1. About the Documentation
This section provides a brief overview of Reactor Netty
reference documentation. You do not
need to read this guide in a linear fashion. Each piece stands on its own, though they
often refer to other pieces.
1.1. Latest Version and Copyright Notice
The Reactor Netty
reference guide is available as HTML
documents. The latest copy is available
at https://projectreactor.io/docs/netty/release/reference/index.html
Copies of this document may be made for your own use and for distribution to others,
provided that you do not charge any fee for such copies and further provided that each
copy contains this Copyright Notice
, whether distributed in print or electronically.
1.2. Contributing to the Documentation
The reference guide is written in Asciidoc, and you can find its sources at https://github.com/reactor/reactor-netty/tree/main/docs/asciidoc.
If you have an improvement, we will be happy to get a pull request from you!
We recommend that you check out a local copy of the repository so that you can
generate the documentation by using the asciidoctor
Gradle task and checking the
rendering. Some of the sections rely on included files, so GitHub
rendering is
not always complete.
To facilitate documentation edits, most sections have a link at the end that opens
an edit UI directly on GitHub for the main source file for that section. These links are
only present in the HTML5 version of this reference guide. They look like the following link:
Suggest Edit to About the Documentation.
|
1.3. Getting Help
There are several ways to reach out for help with Reactor Netty
. You can:
-
Get in touch with the community on Gitter.
-
Ask a question on stackoverflow.com at
reactor-netty
. -
Report bugs in
Github
issues. The repository is the following: reactor-netty.
All of Reactor Netty is open source,
including this
documentation.
|
2. Getting Started
This section contains information that should help you get going with Reactor Netty
. It
includes the following information:
2.1. Introducing Reactor Netty
Suited for Microservices Architecture, Reactor Netty
offers
backpressure-ready network engines for HTTP
(including Websockets), TCP
, and UDP
.
2.2. Prerequisites
Reactor Netty
runs on Java 8
and above.
It has transitive dependencies on:
-
Reactive Streams v1.0.3
-
Reactor Core v3.x
-
Netty v4.1.x
2.3. Understanding the BOM and versioning scheme
Reactor Netty
is part of the Project Reactor BOM
(since the Aluminium
release train).
This curated list groups artifacts that are meant to work well together, providing
the relevant versions despite potentially divergent versioning schemes in these artifacts.
The versioning scheme has changed between 0.9.x and 1.0.x (Dysprosium and Europium). |
Artifacts follow a versioning scheme of MAJOR.MINOR.PATCH-QUALIFIER
while the BOM is versioned using a CalVer inspired scheme of YYYY.MINOR.PATCH-QUALIFIER
, where:
-
MAJOR
is the current generation of Reactor, where each new generation can bring fundamental changes to the structure of the project (which might imply a more significant migration effort) -
YYYY
is the year of the first GA release in a given release cycle (like 1.0.0 for 1.0.x) -
.MINOR
is a 0-based number incrementing with each new release cycle-
in the case of projects, it generally reflects wider changes and can indicate a moderate migration effort
-
in the case of the BOM it allows discerning between release cycles in case two get first released the same year
-
-
.PATCH
is a 0-based number incrementing with each service release -
-QUALIFIER
is a textual qualifier, which is omitted in the case of GA releases (see below)
The first release cycle to follow that convention is thus 2020.0.x
, codename Europium
.
The scheme uses the following qualifiers (note the use of dash separator), in order:
-
-M1
..-M9
: milestones (we don’t expect more than 9 per service release) -
-RC1
..-RC9
: release candidates (we don’t expect more than 9 per service release) -
-SNAPSHOT
: snapshots -
no qualifier for GA releases
Snapshots appear higher in the order above because, conceptually, they’re always "the freshest pre-release" of any given PATCH. Even though the first deployed artifact of a PATCH cycle will always be a -SNAPSHOT, a similarly named but more up-to-date snapshot would also get released after eg. a milestone or between release candidates. |
Each release cycle is also given a codename, in continuity with the previous codename-based scheme, which can be used to reference it more informally (like in discussions, blog posts, etc…). The codenames represent what would traditionally be the MAJOR.MINOR number. They (mostly) come from the Periodic Table of Elements, in increasing alphabetical order.
Up until Dysprosium, the BOM was versioned using a release train scheme with a codename followed by a qualifier, and the qualifiers were slightly different. For example: Aluminium-RELEASE (first GA release, would now be something like YYYY.0.0), Bismuth-M1, Californium-SR1 (service release would now be something like YYYY.0.1), Dysprosium-RC1, Dysprosium-BUILD-SNAPSHOT (after each patch, we’d go back to the same snapshot version. would now be something like YYYY.0.X-SNAPSHOT so we get 1 snapshot per PATCH) |
2.4. Getting Reactor Netty
As mentioned earlier, the easiest way to use
Reactor Netty
in your core is to use the BOM
and
add the relevant dependencies to your project. Note that, when adding such a dependency,
you must omit the version so that the version gets picked up from the BOM
.
However, if you want to force the use of a specific artifact’s version, you can specify
it when adding your dependency as you usually would. You can also forego the BOM
entirely
and specify dependencies by their artifact versions.
2.4.1. Maven Installation
The BOM
concept is natively supported by Maven
. First, you need to import the BOM
by
adding the following snippet to your pom.xml
. If the top section
(dependencyManagement
) already exists in your pom, add only the contents.
<dependencyManagement> (1)
<dependencies>
<dependency>
<groupId>io.projectreactor</groupId>
<artifactId>reactor-bom</artifactId>
<version>2020.0.19</version> (2)
<type>pom</type>
<scope>import</scope>
</dependency>
</dependencies>
</dependencyManagement>
1 | Notice the dependencyManagement tag. This is in addition to the regular
dependencies section. |
2 | As of this writing, 2020.0.19 is the latest version of the BOM .
Check for updates at https://github.com/reactor/reactor/releases. |
Next, add your dependencies to the relevant reactor projects, as usual (except without a
<version>
). The following listing shows how to do so:
<dependencies>
<dependency>
<groupId>io.projectreactor.netty</groupId>
<artifactId>reactor-netty-core</artifactId> (1)
(2)
</dependency>
</dependencies>
<dependencies>
<dependency>
<groupId>io.projectreactor.netty</groupId>
<artifactId>reactor-netty-http</artifactId>
</dependency>
</dependencies>
1 | Dependency on Reactor Netty |
2 | No version tag here |
2.4.2. Gradle Installation
The BOM
concept is supported in Gradle since version 5.
The following listing shows how to import the BOM
and add a dependency to Reactor Netty
:
dependencies {
// import a BOM
implementation platform('io.projectreactor:reactor-bom:2020.0.19') (1)
// define dependencies without versions
implementation 'io.projectreactor.netty:reactor-netty-core' (2)
implementation 'io.projectreactor.netty:reactor-netty-http'
}
1 | As of this writing, 2020.0.19 is the latest version of the BOM .
Check for updates at https://github.com/reactor/reactor/releases. |
2 | There is no third : separated section for the version. It is taken from the BOM . |
2.4.3. Milestones and Snapshots
Milestones and developer previews are distributed through the Spring Milestones
repository rather than Maven Central
. To add it to your build configuration
file, use the following snippet:
<repositories>
<repository>
<id>spring-milestones</id>
<name>Spring Milestones Repository</name>
<url>https://repo.spring.io/milestone</url>
</repository>
</repositories>
For Gradle, use the following snippet:
repositories {
maven { url 'https://repo.spring.io/milestone' }
mavenCentral()
}
Similarly, snapshots are also available in a separate dedicated repository (for both Maven and Gradle):
<repositories>
<repository>
<id>spring-snapshots</id>
<name>Spring Snapshot Repository</name>
<url>https://repo.spring.io/snapshot</url>
</repository>
</repositories>
repositories {
maven { url 'https://repo.spring.io/snapshot' }
mavenCentral()
}
2.5. Support and policies
The entries below are mirroring https://github.com/reactor/.github/blob/main/SUPPORT.adoc
2.5.1. Do you have a question?
Search Stack Overflow first; discuss if necessary |
If you’re unsure why something isn’t working or wondering if there is a better way of doing it please check on Stack Overflow first and if necessary start a discussion. Use relevant tags among the ones we monitor for that purpose:
-
reactor-netty
for specific reactor-netty questions -
project-reactor
for generic reactor questions
If you prefer real-time discussion, we also have a few Gitter channels:
-
reactor
is the historic most active one, where most of the community can help -
reactor-core
is intended for more advanced pinpointed discussions around the inner workings of the library -
reactor-netty
is intended for netty-specific questions
Refer to each project’s README for potential other sources of information.
We generally discourage opening GitHub issues for questions, in favor of the two channels above.
2.5.2. Our policy on deprecations
When dealing with deprecations, given a version A.B.C
, we’ll ensure that:
-
deprecations introduced in version
A
.B
.0
will be removed no sooner than versionA
.B+1
.0
-
deprecations introduced in version
A
.B
.1+
will be removed no sooner than versionA
.B+2
.0
-
we’ll strive to mention the following in the deprecation javadoc:
3. TCP Server
Reactor Netty
provides an easy to use and configure
TcpServer
.
It hides most of the Netty
functionality that is needed to create a TCP
server
and adds Reactive Streams
backpressure.
3.1. Starting and Stopping
To start a TCP
server, you must create and configure a
TcpServer
instance.
By default, the host
is configured for any local address, and the system picks up an ephemeral port
when the bind
operation is invoked. The following example shows how to create and
configure a TcpServer
instance:
import reactor.netty.DisposableServer;
import reactor.netty.tcp.TcpServer;
public class Application {
public static void main(String[] args) {
DisposableServer server =
TcpServer.create() (1)
.bindNow(); (2)
server.onDispose()
.block();
}
}
1 | Creates a TcpServer
instance that is ready for configuring. |
2 | Starts the server in a blocking fashion and waits for it to finish initializing. |
The returned DisposableServer
offers a simple server API, including disposeNow()
,
which shuts the server down in a blocking fashion.
3.1.1. Host and Port
To serve on a specific host
and port
, you can apply the following configuration to the TCP
server:
import reactor.netty.DisposableServer;
import reactor.netty.tcp.TcpServer;
public class Application {
public static void main(String[] args) {
DisposableServer server =
TcpServer.create()
.host("localhost") (1)
.port(8080) (2)
.bindNow();
server.onDispose()
.block();
}
}
1 | Configures the TCP server host |
2 | Configures the TCP server port |
To serve on multiple addresses, after having configured the TcpServer
you can bind it multiple times to obtain separate DisposableServer`s.
All created servers will share resources such as `LoopResources
because they use the same configuration instance under the hood.
import reactor.core.publisher.Mono;
import reactor.netty.DisposableServer;
import reactor.netty.tcp.TcpServer;
public class MultiAddressApplication {
public static void main(String[] args) {
TcpServer tcpServer = TcpServer.create();
DisposableServer server1 = tcpServer
.host("localhost") (1)
.port(8080) (2)
.bindNow();
DisposableServer server2 = tcpServer
.host("0.0.0.0") (3)
.port(8081) (4)
.bindNow();
Mono.when(server1.onDispose(), server2.onDispose())
.block();
}
}
1 | Configures the first TCP server host |
2 | Configures the first TCP server port |
3 | Configures the second TCP server host |
4 | Configures the second TCP server port |
3.2. Eager Initialization
By default, the initialization of the TcpServer
resources happens on demand. This means that the bind
operation
absorbs the extra time needed to initialize and load:
-
the event loop groups
-
the native transport libraries (when native transport is used)
-
the native libraries for the security (in case of
OpenSsl
)
When you need to preload these resources, you can configure the TcpServer
as follows:
import reactor.netty.DisposableServer;
import reactor.netty.tcp.TcpServer;
public class Application {
public static void main(String[] args) {
TcpServer tcpServer =
TcpServer.create()
.handle((inbound, outbound) -> inbound.receive().then());
tcpServer.warmup() (1)
.block();
DisposableServer server = tcpServer.bindNow();
server.onDispose()
.block();
}
}
1 | Initialize and load the event loop groups, the native transport libraries and the native libraries for the security |
3.3. Writing Data
In order to send data to a connected client, you must attach an I/O handler.
The I/O handler has access to NettyOutbound
to be able to write data. The following example shows how to attach an I/O handler:
import reactor.core.publisher.Mono;
import reactor.netty.DisposableServer;
import reactor.netty.tcp.TcpServer;
public class Application {
public static void main(String[] args) {
DisposableServer server =
TcpServer.create()
.handle((inbound, outbound) -> outbound.sendString(Mono.just("hello"))) (1)
.bindNow();
server.onDispose()
.block();
}
}
1 | Sends hello string to the connected clients |
3.4. Consuming Data
In order to receive data from a connected client, you must attach an I/O handler.
The I/O handler has access to NettyInbound
to be able to read data. The following example shows how to use it:
import reactor.netty.DisposableServer;
import reactor.netty.tcp.TcpServer;
public class Application {
public static void main(String[] args) {
DisposableServer server =
TcpServer.create()
.handle((inbound, outbound) -> inbound.receive().then()) (1)
.bindNow();
server.onDispose()
.block();
}
}
1 | Receives data from the connected clients |
3.5. Lifecycle Callbacks
The following lifecycle callbacks are provided to let you extend the TcpServer
:
Callback | Description |
---|---|
|
Invoked when the server channel is about to bind. |
|
Invoked when the server channel is bound. |
|
Invoked when initializing the channel. |
|
Invoked when a remote client is connected |
|
Invoked when the server channel is unbound. |
The following example uses the doOnConnection
and doOnChannelInit
callbacks:
import io.netty.handler.logging.LoggingHandler;
import io.netty.handler.timeout.ReadTimeoutHandler;
import reactor.netty.DisposableServer;
import reactor.netty.tcp.TcpServer;
import java.util.concurrent.TimeUnit;
public class Application {
public static void main(String[] args) {
DisposableServer server =
TcpServer.create()
.doOnConnection(conn ->
conn.addHandlerFirst(new ReadTimeoutHandler(10, TimeUnit.SECONDS))) (1)
.doOnChannelInit((observer, channel, remoteAddress) ->
channel.pipeline()
.addFirst(new LoggingHandler("reactor.netty.examples"))) (2)
.bindNow();
server.onDispose()
.block();
}
}
1 | Netty pipeline is extended with ReadTimeoutHandler when a remote client is connected. |
2 | Netty pipeline is extended with LoggingHandler when initializing the channel. |
3.6. TCP-level Configurations
This section describes three kinds of configuration that you can use at the TCP level:
3.6.1. Setting Channel Options
By default, the TCP
server is configured with the following options:
Map<ChannelOption<?>, Boolean> childOptions = new HashMap<>(2);
childOptions.put(ChannelOption.AUTO_READ, false);
childOptions.put(ChannelOption.TCP_NODELAY, true);
this.config = new TcpServerConfig(
Collections.singletonMap(ChannelOption.SO_REUSEADDR, true),
childOptions,
() -> new InetSocketAddress(DEFAULT_PORT));
}
If additional options are necessary or changes to the current options are needed, you can apply the following configuration:
import io.netty.channel.ChannelOption;
import reactor.netty.DisposableServer;
import reactor.netty.tcp.TcpServer;
public class Application {
public static void main(String[] args) {
DisposableServer server =
TcpServer.create()
.option(ChannelOption.CONNECT_TIMEOUT_MILLIS, 10000)
.bindNow();
server.onDispose()
.block();
}
}
You can find more about Netty
channel options at the following links:
3.6.2. Wire Logger
Reactor Netty provides wire logging for when the traffic between the peers needs to be inspected.
By default, wire logging is disabled.
To enable it, you must set the logger reactor.netty.tcp.TcpServer
level to DEBUG
and apply the following configuration:
import reactor.netty.DisposableServer;
import reactor.netty.tcp.TcpServer;
public class Application {
public static void main(String[] args) {
DisposableServer server =
TcpServer.create()
.wiretap(true) (1)
.bindNow();
server.onDispose()
.block();
}
}
1 | Enables the wire logging |
Wire Logger formatters
Reactor Netty supports 3 different formatters:
-
AdvancedByteBufFormat#HEX_DUMP - the default
/**
* When wire logging is enabled with this format, both events and content will be logged.
* The content will be in hex format.
* <p>Examples:</p>
* <pre>
* {@code
* reactor.netty.http.HttpTests - [d5230a14, L:/0:0:0:0:0:0:0:1:60267 - R:/0:0:0:0:0:0:0:1:60269] REGISTERED
* reactor.netty.http.HttpTests - [d5230a14, L:/0:0:0:0:0:0:0:1:60267 - R:/0:0:0:0:0:0:0:1:60269] ACTIVE
* reactor.netty.http.HttpTests - [d5230a14, L:/0:0:0:0:0:0:0:1:60267 - R:/0:0:0:0:0:0:0:1:60269] READ: 145B
* +-------------------------------------------------+
* | 0 1 2 3 4 5 6 7 8 9 a b c d e f |
* +--------+-------------------------------------------------+----------------+
* |00000000| 50 4f 53 54 20 2f 74 65 73 74 2f 57 6f 72 6c 64 |POST /test/World|
* |00000010| 20 48 54 54 50 2f 31 2e 31 0d 0a 43 6f 6e 74 65 | HTTP/1.1..Conte|
* |00000020| 6e 74 2d 54 79 70 65 3a 20 74 65 78 74 2f 70 6c |nt-Type: text/pl|
* |00000030| 61 69 6e 0d 0a 75 73 65 72 2d 61 67 65 6e 74 3a |ain..user-agent:|
* |00000040| 20 52 65 61 63 74 6f 72 4e 65 74 74 79 2f 64 65 | ReactorNetty/de|
* ...
* reactor.netty.http.HttpTests - [d5230a14, L:/0:0:0:0:0:0:0:1:60267 - R:/0:0:0:0:0:0:0:1:60269] WRITE: 38B
* +-------------------------------------------------+
* | 0 1 2 3 4 5 6 7 8 9 a b c d e f |
* +--------+-------------------------------------------------+----------------+
* |00000000| 48 54 54 50 2f 31 2e 31 20 32 30 30 20 4f 4b 0d |HTTP/1.1 200 OK.|
* |00000010| 0a 63 6f 6e 74 65 6e 74 2d 6c 65 6e 67 74 68 3a |.content-length:|
* |00000020| 20 30 0d 0a 0d 0a | 0.... |
* +--------+-------------------------------------------------+----------------+
* }
* </pre>
*/
/**
* When wire logging is enabled with this format, only the events will be logged.
* <p>Examples:</p>
* <pre>
* {@code
* reactor.netty.http.HttpTests - [230d3686, L:/0:0:0:0:0:0:0:1:60241 - R:/0:0:0:0:0:0:0:1:60245] REGISTERED
* reactor.netty.http.HttpTests - [230d3686, L:/0:0:0:0:0:0:0:1:60241 - R:/0:0:0:0:0:0:0:1:60245] ACTIVE
* reactor.netty.http.HttpTests - [230d3686, L:/0:0:0:0:0:0:0:1:60241 - R:/0:0:0:0:0:0:0:1:60245] READ: 145B
* reactor.netty.http.HttpTests - [230d3686, L:/0:0:0:0:0:0:0:1:60241 - R:/0:0:0:0:0:0:0:1:60245] WRITE: 38B
* }
* </pre>
*/
/**
* When wire logging is enabled with this format, both events and content will be logged.
* The content will be in plain text format.
* <p>Examples:</p>
* <pre>
* {@code
* reactor.netty.http.HttpTests - [02c3db6c, L:/0:0:0:0:0:0:0:1:60317 - R:/0:0:0:0:0:0:0:1:60319] REGISTERED
* reactor.netty.http.HttpTests - [02c3db6c, L:/0:0:0:0:0:0:0:1:60317 - R:/0:0:0:0:0:0:0:1:60319] ACTIVE
* reactor.netty.http.HttpTests - [02c3db6c, L:/0:0:0:0:0:0:0:1:60317 - R:/0:0:0:0:0:0:0:1:60319] READ: 145B POST /test/World HTTP/1.1
* Content-Type: text/plain
* user-agent: ReactorNetty/dev
* ...
* reactor.netty.http.HttpTests - [02c3db6c, L:/0:0:0:0:0:0:0:1:60317 - R:/0:0:0:0:0:0:0:1:60319] WRITE: 38B HTTP/1.1 200 OK
* content-length: 0
* }
* </pre>
*/
When you need to change the default formatter you can configure it as follows:
import io.netty.handler.logging.LogLevel;
import reactor.netty.DisposableServer;
import reactor.netty.tcp.TcpServer;
import reactor.netty.transport.logging.AdvancedByteBufFormat;
public class Application {
public static void main(String[] args) {
DisposableServer server =
TcpServer.create()
.wiretap("logger-name", LogLevel.DEBUG, AdvancedByteBufFormat.TEXTUAL) (1)
.bindNow();
server.onDispose()
.block();
}
}
1 | Enables the wire logging, AdvancedByteBufFormat#TEXTUAL is used for printing the content. |
3.6.3. Using an Event Loop Group
By default, the TCP
server uses an “Event Loop Group,” where the number of the worker threads equals the number of
processors available to the runtime on initialization (but with a minimum value of 4). When you need a different configuration,
you can use one of the LoopResource#create
methods.
The default configuration for the Event Loop Group
is the following:
/**
* Default worker thread count, fallback to available processor
* (but with a minimum value of 4)
*/
public static final String IO_WORKER_COUNT = "reactor.netty.ioWorkerCount";
/**
* Default selector thread count, fallback to -1 (no selector thread)
*/
public static final String IO_SELECT_COUNT = "reactor.netty.ioSelectCount";
/**
* Default worker thread count for UDP, fallback to available processor
* (but with a minimum value of 4)
*/
public static final String UDP_IO_THREAD_COUNT = "reactor.netty.udp.ioThreadCount";
/**
* Default quiet period that guarantees that the disposal of the underlying LoopResources
* will not happen, fallback to 2 seconds.
*/
public static final String SHUTDOWN_QUIET_PERIOD = "reactor.netty.ioShutdownQuietPeriod";
/**
* Default maximum amount of time to wait until the disposal of the underlying LoopResources
* regardless if a task was submitted during the quiet period, fallback to 15 seconds.
*/
public static final String SHUTDOWN_TIMEOUT = "reactor.netty.ioShutdownTimeout";
/**
* Default value whether the native transport (epoll, kqueue) will be preferred,
* fallback it will be preferred when available
*/
public static final String NATIVE = "reactor.netty.native";
If changes to the these settings are needed, you can apply the following configuration:
import reactor.netty.DisposableServer;
import reactor.netty.resources.LoopResources;
import reactor.netty.tcp.TcpServer;
public class Application {
public static void main(String[] args) {
LoopResources loop = LoopResources.create("event-loop", 1, 4, true);
DisposableServer server =
TcpServer.create()
.runOn(loop)
.bindNow();
server.onDispose()
.block();
}
}
3.7. SSL and TLS
When you need SSL or TLS, you can apply the configuration shown in the next listing.
By default, if OpenSSL
is available,
SslProvider.OPENSSL
provider is used as a provider. Otherwise
SslProvider.JDK
is used.
Switching the provider can be done through
SslContextBuilder
or by setting -Dio.netty.handler.ssl.noOpenSsl=true
.
The following example uses SslContextBuilder
:
import reactor.netty.DisposableServer;
import reactor.netty.tcp.TcpServer;
import reactor.netty.tcp.TcpSslContextSpec;
import java.io.File;
public class Application {
public static void main(String[] args) {
File cert = new File("certificate.crt");
File key = new File("private.key");
TcpSslContextSpec tcpSslContextSpec = TcpSslContextSpec.forServer(cert, key);
DisposableServer server =
TcpServer.create()
.secure(spec -> spec.sslContext(tcpSslContextSpec))
.bindNow();
server.onDispose()
.block();
}
}
3.7.1. Server Name Indication
You can configure the TCP
server with multiple SslContext
mapped to a specific domain.
An exact domain name or a domain name containing a wildcard can be used when configuring the SNI
mapping.
The following example uses a domain name containing a wildcard:
import io.netty.handler.ssl.SslContext;
import io.netty.handler.ssl.SslContextBuilder;
import reactor.netty.DisposableServer;
import reactor.netty.tcp.TcpServer;
import java.io.File;
public class Application {
public static void main(String[] args) throws Exception {
File defaultCert = new File("default_certificate.crt");
File defaultKey = new File("default_private.key");
File testDomainCert = new File("default_certificate.crt");
File testDomainKey = new File("default_private.key");
SslContext defaultSslContext = SslContextBuilder.forServer(defaultCert, defaultKey).build();
SslContext testDomainSslContext = SslContextBuilder.forServer(testDomainCert, testDomainKey).build();
DisposableServer server =
TcpServer.create()
.secure(spec -> spec.sslContext(defaultSslContext)
.addSniMapping("*.test.com",
testDomainSpec -> testDomainSpec.sslContext(testDomainSslContext)))
.bindNow();
server.onDispose()
.block();
}
}
3.8. Metrics
The TCP server supports built-in integration with Micrometer
.
It exposes all metrics with a prefix of reactor.netty.tcp.server
.
The following table provides information for the TCP server metrics:
metric name | type | description |
---|---|---|
reactor.netty.tcp.server.connections.total |
Gauge |
The number of all opened connections |
reactor.netty.tcp.server.data.received |
DistributionSummary |
Amount of the data received, in bytes |
reactor.netty.tcp.server.data.sent |
DistributionSummary |
Amount of the data sent, in bytes |
reactor.netty.tcp.server.errors |
Counter |
Number of errors that occurred |
reactor.netty.tcp.server.tls.handshake.time |
Timer |
Time spent for TLS handshake |
These additional metrics are also available:
ByteBufAllocator
metrics
metric name | type | description |
---|---|---|
reactor.netty.bytebuf.allocator.used.heap.memory |
Gauge |
The number of bytes reserved by heap buffer allocator |
reactor.netty.bytebuf.allocator.used.direct.memory |
Gauge |
The number of bytes reserved by direct buffer allocator |
reactor.netty.bytebuf.allocator.used.heap.arenas |
Gauge |
The number of heap arenas (when |
reactor.netty.bytebuf.allocator.used.direct.arenas |
Gauge |
The number of direct arenas (when |
reactor.netty.bytebuf.allocator.used.threadlocal.caches |
Gauge |
The number of thread local caches (when |
reactor.netty.bytebuf.allocator.used.small.cache.size |
Gauge |
The size of the small cache (when |
reactor.netty.bytebuf.allocator.used.normal.cache.size |
Gauge |
The size of the normal cache (when |
reactor.netty.bytebuf.allocator.used.chunk.size |
Gauge |
The chunk size for an arena (when |
reactor.netty.bytebuf.allocator.active.heap.buffers |
Gauge |
The actual bytes consumed by in-use heap buffers (when |
reactor.netty.bytebuf.allocator.active.direct.buffers |
Gauge |
The actual bytes consumed by in-use direct buffers (when |
EventLoop
metrics
metric name | type | description |
---|---|---|
reactor.netty.eventloop.pending.tasks |
Gauge |
The number of tasks that are pending for processing on an event loop |
The following example enables that integration:
import reactor.netty.DisposableServer;
import reactor.netty.tcp.TcpServer;
public class Application {
public static void main(String[] args) {
DisposableServer server =
TcpServer.create()
.metrics(true) (1)
.bindNow();
server.onDispose()
.block();
}
}
1 | Enables the built-in integration with Micrometer |
When TCP server metrics are needed for an integration with a system other than Micrometer
or you want
to provide your own integration with Micrometer
, you can provide your own metrics recorder, as follows:
import reactor.netty.DisposableServer;
import reactor.netty.channel.ChannelMetricsRecorder;
import reactor.netty.tcp.TcpServer;
import java.net.SocketAddress;
import java.time.Duration;
public class Application {
public static void main(String[] args) {
DisposableServer server =
TcpServer.create()
.metrics(true, CustomChannelMetricsRecorder::new) (1)
.bindNow();
server.onDispose()
.block();
}
1 | Enables TCP server metrics and provides ChannelMetricsRecorder implementation. |
3.9. Unix Domain Sockets
The TCP
server supports Unix Domain Sockets (UDS) when native transport is in use.
The following example shows how to use UDS support:
import io.netty.channel.unix.DomainSocketAddress;
import reactor.netty.DisposableServer;
import reactor.netty.tcp.TcpServer;
public class Application {
public static void main(String[] args) {
DisposableServer server =
TcpServer.create()
.bindAddress(() -> new DomainSocketAddress("/tmp/test.sock")) (1)
.bindNow();
server.onDispose()
.block();
}
}
1 | Specifies DomainSocketAddress that will be used |
Suggest Edit to "TCP Server"
4. TCP Client
Reactor Netty provides the easy-to-use and easy-to-configure
TcpClient
.
It hides most of the Netty functionality that is needed in order to create a TCP
client
and adds Reactive Streams backpressure.
4.1. Connect and Disconnect
To connect the TCP
client to a given endpoint, you must create and configure a
TcpClient
instance.
By default, the host
is localhost
and the port
is 12012
.
The following example shows how to create a TcpClient
:
import reactor.netty.Connection;
import reactor.netty.tcp.TcpClient;
public class Application {
public static void main(String[] args) {
Connection connection =
TcpClient.create() (1)
.connectNow(); (2)
connection.onDispose()
.block();
}
}
1 | Creates a TcpClient
instance that is ready for configuring. |
2 | Connects the client in a blocking fashion and waits for it to finish initializing. |
The returned Connection
offers a simple connection API, including disposeNow()
,
which shuts the client down in a blocking fashion.
4.1.1. Host and Port
To connect to a specific host
and port
, you can apply the following configuration to the TCP
client.
The following example shows how to do so:
import reactor.netty.Connection;
import reactor.netty.tcp.TcpClient;
public class Application {
public static void main(String[] args) {
Connection connection =
TcpClient.create()
.host("example.com") (1)
.port(80) (2)
.connectNow();
connection.onDispose()
.block();
}
}
1 | Configures the TCP host |
2 | Configures the TCP port |
4.2. Eager Initialization
By default, the initialization of the TcpClient
resources happens on demand. This means that the connect
operation
absorbs the extra time needed to initialize and load:
-
the event loop group
-
the host name resolver
-
the native transport libraries (when native transport is used)
-
the native libraries for the security (in case of
OpenSsl
)
When you need to preload these resources, you can configure the TcpClient
as follows:
import reactor.core.publisher.Mono;
import reactor.netty.Connection;
import reactor.netty.tcp.TcpClient;
public class Application {
public static void main(String[] args) {
TcpClient tcpClient =
TcpClient.create()
.host("example.com")
.port(80)
.handle((inbound, outbound) -> outbound.sendString(Mono.just("hello")));
tcpClient.warmup() (1)
.block();
Connection connection = tcpClient.connectNow(); (2)
connection.onDispose()
.block();
}
}
1 | Initialize and load the event loop group, the host name resolver, the native transport libraries and the native libraries for the security |
2 | Host name resolution happens when connecting to the remote peer |
4.3. Writing Data
To send data to a given endpoint, you must attach an I/O handler.
The I/O handler has access to NettyOutbound
to be able to write data.
import reactor.core.publisher.Mono;
import reactor.netty.Connection;
import reactor.netty.tcp.TcpClient;
public class Application {
public static void main(String[] args) {
Connection connection =
TcpClient.create()
.host("example.com")
.port(80)
.handle((inbound, outbound) -> outbound.sendString(Mono.just("hello"))) (1)
.connectNow();
connection.onDispose()
.block();
}
}
1 | Sends hello string to the endpoint. |
When you need more control over the writing process, as an alternative for I/O handler you may use
Connection#outbound
. As opposed to I/O handler
where the connection is closed when the provided Publisher
finishes (in case of finite Publisher
),
when using Connection#outbound
, you have to invoke explicitly
Connection#dispose
in order to close the connection.
import reactor.core.publisher.Mono;
import reactor.netty.Connection;
import reactor.netty.tcp.TcpClient;
public class Application {
public static void main(String[] args) {
Connection connection =
TcpClient.create()
.host("example.com")
.port(80)
.connectNow();
connection.outbound()
.sendString(Mono.just("hello 1")) (1)
.then()
.subscribe();
connection.outbound()
.sendString(Mono.just("hello 2")) (2)
.then()
.subscribe(null, null, connection::dispose); (3)
connection.onDispose()
.block();
}
}
1 | Sends hello 1 string to the endpoint. |
2 | Sends hello 2 string to the endpoint. |
3 | Closes the connection once the message is sent to the endpoint. |
4.4. Consuming Data
To receive data from a given endpoint, you must attach an I/O handler.
The I/O handler has access to NettyInbound
to be able to read data. The following example shows how to do so:
import reactor.netty.Connection;
import reactor.netty.tcp.TcpClient;
public class Application {
public static void main(String[] args) {
Connection connection =
TcpClient.create()
.host("example.com")
.port(80)
.handle((inbound, outbound) -> inbound.receive().then()) (1)
.connectNow();
connection.onDispose()
.block();
}
}
1 | Receives data from a given endpoint |
When you need more control over the reading process, as an alternative for I/O handler you may use
Connection#inbound
. As opposed to I/O handler
where the connection is closed when the provided Publisher
finishes (in case of finite Publisher
),
when using Connection#inbound
, you have to invoke explicitly
Connection#dispose
in order to close the connection.
import reactor.netty.Connection;
import reactor.netty.tcp.TcpClient;
public class Application {
public static void main(String[] args) {
Connection connection =
TcpClient.create()
.host("example.com")
.port(80)
.connectNow();
connection.inbound()
.receive() (1)
.then()
.subscribe();
connection.onDispose()
.block();
}
}
1 | Receives data from a given endpoint. |
4.5. Lifecycle Callbacks
The following lifecycle callbacks are provided to let you extend the TcpClient
.
Callback | Description |
---|---|
|
Invoked after the remote address has been resolved successfully. |
|
Invoked when initializing the channel. |
|
Invoked when the channel is about to connect. |
|
Invoked after the channel has been connected. |
|
Invoked after the channel has been disconnected. |
|
Invoked when the remote address is about to be resolved. |
|
Invoked in case the remote address hasn’t been resolved successfully. |
The following example uses the doOnConnected
and doOnChannelInit
callbacks:
import io.netty.handler.logging.LoggingHandler;
import io.netty.handler.timeout.ReadTimeoutHandler;
import reactor.netty.Connection;
import reactor.netty.tcp.TcpClient;
import java.util.concurrent.TimeUnit;
public class Application {
public static void main(String[] args) {
Connection connection =
TcpClient.create()
.host("example.com")
.port(80)
.doOnConnected(conn ->
conn.addHandlerFirst(new ReadTimeoutHandler(10, TimeUnit.SECONDS))) (1)
.doOnChannelInit((observer, channel, remoteAddress) ->
channel.pipeline()
.addFirst(new LoggingHandler("reactor.netty.examples"))) (2)
.connectNow();
connection.onDispose()
.block();
}
}
1 | Netty pipeline is extended with ReadTimeoutHandler when the channel has been connected. |
2 | Netty pipeline is extended with LoggingHandler when initializing the channel. |
4.6. TCP-level Configurations
This section describes three kinds of configuration that you can use at the TCP level:
4.6.1. Channel Options
By default, the TCP
client is configured with the following options:
this.config = new TcpClientConfig(
provider,
Collections.singletonMap(ChannelOption.AUTO_READ, false),
() -> AddressUtils.createUnresolved(NetUtil.LOCALHOST.getHostAddress(), DEFAULT_PORT));
}
If additional options are necessary or changes to the current options are needed, you can apply the following configuration:
import io.netty.channel.ChannelOption;
import reactor.netty.Connection;
import reactor.netty.tcp.TcpClient;
public class Application {
public static void main(String[] args) {
Connection connection =
TcpClient.create()
.host("example.com")
.port(80)
.option(ChannelOption.CONNECT_TIMEOUT_MILLIS, 10000)
.connectNow();
connection.onDispose()
.block();
}
}
You can find more about Netty
channel options at the following links:
4.6.2. Wire Logger
Reactor Netty provides wire logging for when the traffic between the peers needs to be inspected.
By default, wire logging is disabled.
To enable it, you must set the logger reactor.netty.tcp.TcpClient
level to DEBUG
and apply the following configuration:
import reactor.netty.Connection;
import reactor.netty.tcp.TcpClient;
public class Application {
public static void main(String[] args) {
Connection connection =
TcpClient.create()
.wiretap(true) (1)
.host("example.com")
.port(80)
.connectNow();
connection.onDispose()
.block();
1 | Enables the wire logging |
Wire Logger formatters
Reactor Netty supports 3 different formatters:
-
AdvancedByteBufFormat#HEX_DUMP - the default
/**
* When wire logging is enabled with this format, both events and content will be logged.
* The content will be in hex format.
* <p>Examples:</p>
* <pre>
* {@code
* reactor.netty.http.HttpTests - [d5230a14, L:/0:0:0:0:0:0:0:1:60267 - R:/0:0:0:0:0:0:0:1:60269] REGISTERED
* reactor.netty.http.HttpTests - [d5230a14, L:/0:0:0:0:0:0:0:1:60267 - R:/0:0:0:0:0:0:0:1:60269] ACTIVE
* reactor.netty.http.HttpTests - [d5230a14, L:/0:0:0:0:0:0:0:1:60267 - R:/0:0:0:0:0:0:0:1:60269] READ: 145B
* +-------------------------------------------------+
* | 0 1 2 3 4 5 6 7 8 9 a b c d e f |
* +--------+-------------------------------------------------+----------------+
* |00000000| 50 4f 53 54 20 2f 74 65 73 74 2f 57 6f 72 6c 64 |POST /test/World|
* |00000010| 20 48 54 54 50 2f 31 2e 31 0d 0a 43 6f 6e 74 65 | HTTP/1.1..Conte|
* |00000020| 6e 74 2d 54 79 70 65 3a 20 74 65 78 74 2f 70 6c |nt-Type: text/pl|
* |00000030| 61 69 6e 0d 0a 75 73 65 72 2d 61 67 65 6e 74 3a |ain..user-agent:|
* |00000040| 20 52 65 61 63 74 6f 72 4e 65 74 74 79 2f 64 65 | ReactorNetty/de|
* ...
* reactor.netty.http.HttpTests - [d5230a14, L:/0:0:0:0:0:0:0:1:60267 - R:/0:0:0:0:0:0:0:1:60269] WRITE: 38B
* +-------------------------------------------------+
* | 0 1 2 3 4 5 6 7 8 9 a b c d e f |
* +--------+-------------------------------------------------+----------------+
* |00000000| 48 54 54 50 2f 31 2e 31 20 32 30 30 20 4f 4b 0d |HTTP/1.1 200 OK.|
* |00000010| 0a 63 6f 6e 74 65 6e 74 2d 6c 65 6e 67 74 68 3a |.content-length:|
* |00000020| 20 30 0d 0a 0d 0a | 0.... |
* +--------+-------------------------------------------------+----------------+
* }
* </pre>
*/
/**
* When wire logging is enabled with this format, only the events will be logged.
* <p>Examples:</p>
* <pre>
* {@code
* reactor.netty.http.HttpTests - [230d3686, L:/0:0:0:0:0:0:0:1:60241 - R:/0:0:0:0:0:0:0:1:60245] REGISTERED
* reactor.netty.http.HttpTests - [230d3686, L:/0:0:0:0:0:0:0:1:60241 - R:/0:0:0:0:0:0:0:1:60245] ACTIVE
* reactor.netty.http.HttpTests - [230d3686, L:/0:0:0:0:0:0:0:1:60241 - R:/0:0:0:0:0:0:0:1:60245] READ: 145B
* reactor.netty.http.HttpTests - [230d3686, L:/0:0:0:0:0:0:0:1:60241 - R:/0:0:0:0:0:0:0:1:60245] WRITE: 38B
* }
* </pre>
*/
/**
* When wire logging is enabled with this format, both events and content will be logged.
* The content will be in plain text format.
* <p>Examples:</p>
* <pre>
* {@code
* reactor.netty.http.HttpTests - [02c3db6c, L:/0:0:0:0:0:0:0:1:60317 - R:/0:0:0:0:0:0:0:1:60319] REGISTERED
* reactor.netty.http.HttpTests - [02c3db6c, L:/0:0:0:0:0:0:0:1:60317 - R:/0:0:0:0:0:0:0:1:60319] ACTIVE
* reactor.netty.http.HttpTests - [02c3db6c, L:/0:0:0:0:0:0:0:1:60317 - R:/0:0:0:0:0:0:0:1:60319] READ: 145B POST /test/World HTTP/1.1
* Content-Type: text/plain
* user-agent: ReactorNetty/dev
* ...
* reactor.netty.http.HttpTests - [02c3db6c, L:/0:0:0:0:0:0:0:1:60317 - R:/0:0:0:0:0:0:0:1:60319] WRITE: 38B HTTP/1.1 200 OK
* content-length: 0
* }
* </pre>
*/
When you need to change the default formatter you can configure it as follows:
import io.netty.handler.logging.LogLevel;
import reactor.netty.Connection;
import reactor.netty.tcp.TcpClient;
import reactor.netty.transport.logging.AdvancedByteBufFormat;
public class Application {
public static void main(String[] args) {
Connection connection =
TcpClient.create()
.wiretap("logger-name", LogLevel.DEBUG, AdvancedByteBufFormat.TEXTUAL) (1)
.host("example.com")
.port(80)
.connectNow();
connection.onDispose()
.block();
1 | Enables the wire logging, AdvancedByteBufFormat#TEXTUAL is used for printing the content. |
4.6.3. Event Loop Group
By default the TCP
client uses an “Event Loop Group”, where the number of the worker threads equals the number of
processors available to the runtime on initialization (but with a minimum value of 4). When you need a different configuration,
you can use one of the LoopResource#create
methods.
The following listing shows the default configuration for the Event Loop Group:
/**
* Default worker thread count, fallback to available processor
* (but with a minimum value of 4)
*/
public static final String IO_WORKER_COUNT = "reactor.netty.ioWorkerCount";
/**
* Default selector thread count, fallback to -1 (no selector thread)
*/
public static final String IO_SELECT_COUNT = "reactor.netty.ioSelectCount";
/**
* Default worker thread count for UDP, fallback to available processor
* (but with a minimum value of 4)
*/
public static final String UDP_IO_THREAD_COUNT = "reactor.netty.udp.ioThreadCount";
/**
* Default quiet period that guarantees that the disposal of the underlying LoopResources
* will not happen, fallback to 2 seconds.
*/
public static final String SHUTDOWN_QUIET_PERIOD = "reactor.netty.ioShutdownQuietPeriod";
/**
* Default maximum amount of time to wait until the disposal of the underlying LoopResources
* regardless if a task was submitted during the quiet period, fallback to 15 seconds.
*/
public static final String SHUTDOWN_TIMEOUT = "reactor.netty.ioShutdownTimeout";
/**
* Default value whether the native transport (epoll, kqueue) will be preferred,
* fallback it will be preferred when available
*/
public static final String NATIVE = "reactor.netty.native";
If you need changes to the these settings, you can apply the following configuration:
import reactor.netty.Connection;
import reactor.netty.resources.LoopResources;
import reactor.netty.tcp.TcpClient;
public class Application {
public static void main(String[] args) {
LoopResources loop = LoopResources.create("event-loop", 1, 4, true);
Connection connection =
TcpClient.create()
.host("example.com")
.port(80)
.runOn(loop)
.connectNow();
connection.onDispose()
.block();
}
}
4.7. Connection Pool
By default, TcpClient
uses a “fixed” connection pool with 500
as the maximum number of active channels
and 1000
as the maximum number of further channel acquisition attempts allowed to be kept in a pending state
(for the rest of the configurations check the system properties or the builder configurations below).
This means that the implementation creates a new channel if someone tries to acquire a channel
as long as less than 500
have been created and are managed by the pool.
When the maximum number of channels in the pool is reached, up to 1000
new attempts to
acquire a channel are delayed (pending) until a channel is closed (and thus a slot is free and a new connection can be opened),
and further attempts are declined with an error.
Connections used by the TcpClient are never returned to the pool, but closed. When a connection is closed, a slot is freed
in the pool and thus a new connection can be opened when needed. This behaviour is specific only for TcpClient
and is intentional because only the user/framework knows if the actual protocol is compatible with reusing connections.
(opposed to HttpClient where the protocol is known and Reactor Netty can return the connection to the pool when this is possible)
|
/**
* Default max connections. Fallback to
* 2 * available number of processors (but with a minimum value of 16)
*/
public static final String POOL_MAX_CONNECTIONS = "reactor.netty.pool.maxConnections";
/**
* Default acquisition timeout (milliseconds) before error. If -1 will never wait to
* acquire before opening a new
* connection in an unbounded fashion. Fallback 45 seconds
*/
public static final String POOL_ACQUIRE_TIMEOUT = "reactor.netty.pool.acquireTimeout";
When you need to change the default settings, you can configure the ConnectionProvider
as follows:
import reactor.netty.Connection;
import reactor.netty.resources.ConnectionProvider;
import reactor.netty.tcp.TcpClient;
import java.time.Duration;
public class Application {
public static void main(String[] args) {
ConnectionProvider provider =
ConnectionProvider.builder("fixed")
.maxConnections(50)
.pendingAcquireTimeout(Duration.ofSeconds(60)) (1)
.build();
Connection connection =
TcpClient.create(provider)
.host("example.com")
.port(80)
.connectNow();
connection.onDispose()
.block();
}
}
1 | Configures the maximum time for the pending acquire operation to 60 seconds. |
The following listing shows the available configurations:
Configuration name | Description |
---|---|
|
When this option is enabled, connection pools are regularly checked in the background, and those that are empty and been inactive for a specified time become eligible for disposal. By default, this background disposal of inactive pools is disabled. |
|
When |
|
The maximum number of connections (per connection pool) before start pending. Default to 2 * available number of processors (but with a minimum value of 16). |
|
Enables/disables built-in integration with Micrometer. |
|
The maximum number of extra attempts at acquiring a connection to keep in a pending queue. If -1 is specified, the pending queue does not have upper limit. Default to 2 * max connections. |
|
The maximum time before which a pending acquire must complete, or a TimeoutException is thrown (resolution: ms). If -1 is specified, no such timeout is applied. Default: 45 seconds. |
If you need to disable the connection pool, you can apply the following configuration:
import reactor.netty.Connection;
import reactor.netty.tcp.TcpClient;
public class Application {
public static void main(String[] args) {
Connection connection =
TcpClient.newConnection()
.host("example.com")
.port(80)
.connectNow();
connection.onDispose()
.block();
}
}
4.7.1. Metrics
The pooled ConnectionProvider
supports built-in integration with Micrometer
.
It exposes all metrics with a prefix of reactor.netty.connection.provider
.
Pooled ConnectionProvider
metrics
metric name | type | description |
---|---|---|
reactor.netty.connection.provider.total.connections |
Gauge |
The number of all connections, active or idle |
reactor.netty.connection.provider.active.connections |
Gauge |
The number of the connections that have been successfully acquired and are in active use |
reactor.netty.connection.provider.max.connections |
Gauge |
The maximum number of active connections that are allowed |
reactor.netty.connection.provider.idle.connections |
Gauge |
The number of the idle connections |
reactor.netty.connection.provider.pending.connections |
Gauge |
The number of requests that are waiting for a connection |
reactor.netty.connection.provider.max.pending.connections |
Gauge |
The maximum number of requests that will be queued while waiting for a ready connection |
The following example enables that integration:
import reactor.netty.Connection;
import reactor.netty.resources.ConnectionProvider;
import reactor.netty.tcp.TcpClient;
public class Application {
public static void main(String[] args) {
ConnectionProvider provider =
ConnectionProvider.builder("fixed")
.maxConnections(50)
.metrics(true) (1)
.build();
Connection connection =
TcpClient.create(provider)
.host("example.com")
.port(80)
.connectNow();
connection.onDispose()
.block();
}
}
1 | Enables the built-in integration with Micrometer |
4.8. SSL and TLS
When you need SSL or TLS, you can apply the following configuration.
By default, if OpenSSL
is available, the
SslProvider.OPENSSL
provider is used as a provider. Otherwise, the provider is
SslProvider.JDK.
You can switch the provider by using
SslContextBuilder
or by setting -Dio.netty.handler.ssl.noOpenSsl=true
.
The following example uses SslContextBuilder
:
import reactor.netty.Connection;
import reactor.netty.tcp.TcpClient;
import reactor.netty.tcp.TcpSslContextSpec;
public class Application {
public static void main(String[] args) {
TcpSslContextSpec tcpSslContextSpec = TcpSslContextSpec.forClient();
Connection connection =
TcpClient.create()
.host("example.com")
.port(443)
.secure(spec -> spec.sslContext(tcpSslContextSpec))
.connectNow();
connection.onDispose()
.block();
}
}
4.8.1. Server Name Indication
By default, the TCP
client sends the remote host name as SNI
server name.
When you need to change this default setting, you can configure the TCP
client as follows:
import io.netty.handler.ssl.SslContext;
import io.netty.handler.ssl.SslContextBuilder;
import reactor.netty.Connection;
import reactor.netty.tcp.TcpClient;
import javax.net.ssl.SNIHostName;
public class Application {
public static void main(String[] args) throws Exception {
SslContext sslContext = SslContextBuilder.forClient().build();
Connection connection =
TcpClient.create()
.host("127.0.0.1")
.port(8080)
.secure(spec -> spec.sslContext(sslContext)
.serverNames(new SNIHostName("test.com")))
.connectNow();
connection.onDispose()
.block();
}
}
4.9. Proxy Support
Reactor Netty supports the proxy functionality provided by Netty and provides a way
to specify non proxy hosts
through the ProxyProvider
builder.
Netty’s HTTP proxy support always uses CONNECT
method in order to establish a tunnel to the specified proxy regardless of the scheme that is used http
or https
.
(More information: Netty enforce HTTP proxy to support HTTP CONNECT method).
Some proxies might not support CONNECT
method when the scheme is http
or might need to be configured in order to support this way of communication.
Sometimes this might be the reason for not being able to connect to the proxy. Consider checking the proxy documentation
whether it supports or needs an additional configuration in order to support CONNECT
method.
The following example uses ProxyProvider
:
import reactor.netty.Connection;
import reactor.netty.transport.ProxyProvider;
import reactor.netty.tcp.TcpClient;
public class Application {
public static void main(String[] args) {
Connection connection =
TcpClient.create()
.host("example.com")
.port(80)
.proxy(spec -> spec.type(ProxyProvider.Proxy.SOCKS4)
.host("proxy")
.port(8080)
.nonProxyHosts("localhost")
.connectTimeoutMillis(20_000)) (1)
.connectNow();
connection.onDispose()
.block();
}
1 | Configures the connection establishment timeout to 20 seconds. |
4.10. Metrics
The TCP client supports built-in integration with Micrometer
.
It exposes all metrics with a prefix of reactor.netty.tcp.client
.
The following table provides information for the TCP client metrics:
metric name | type | description |
---|---|---|
reactor.netty.tcp.client.data.received |
DistributionSummary |
Amount of the data received, in bytes |
reactor.netty.tcp.client.data.sent |
DistributionSummary |
Amount of the data sent, in bytes |
reactor.netty.tcp.client.errors |
Counter |
Number of errors that occurred |
reactor.netty.tcp.client.tls.handshake.time |
Timer |
Time spent for TLS handshake |
reactor.netty.tcp.client.connect.time |
Timer |
Time spent for connecting to the remote address |
reactor.netty.tcp.client.address.resolver |
Timer |
Time spent for resolving the address |
These additional metrics are also available:
Pooled ConnectionProvider
metrics
metric name | type | description |
---|---|---|
reactor.netty.connection.provider.total.connections |
Gauge |
The number of all connections, active or idle |
reactor.netty.connection.provider.active.connections |
Gauge |
The number of the connections that have been successfully acquired and are in active use |
reactor.netty.connection.provider.max.connections |
Gauge |
The maximum number of active connections that are allowed |
reactor.netty.connection.provider.idle.connections |
Gauge |
The number of the idle connections |
reactor.netty.connection.provider.pending.connections |
Gauge |
The number of requests that are waiting for a connection |
reactor.netty.connection.provider.max.pending.connections |
Gauge |
The maximum number of requests that will be queued while waiting for a ready connection |
ByteBufAllocator
metrics
metric name | type | description |
---|---|---|
reactor.netty.bytebuf.allocator.used.heap.memory |
Gauge |
The number of bytes reserved by heap buffer allocator |
reactor.netty.bytebuf.allocator.used.direct.memory |
Gauge |
The number of bytes reserved by direct buffer allocator |
reactor.netty.bytebuf.allocator.used.heap.arenas |
Gauge |
The number of heap arenas (when |
reactor.netty.bytebuf.allocator.used.direct.arenas |
Gauge |
The number of direct arenas (when |
reactor.netty.bytebuf.allocator.used.threadlocal.caches |
Gauge |
The number of thread local caches (when |
reactor.netty.bytebuf.allocator.used.small.cache.size |
Gauge |
The size of the small cache (when |
reactor.netty.bytebuf.allocator.used.normal.cache.size |
Gauge |
The size of the normal cache (when |
reactor.netty.bytebuf.allocator.used.chunk.size |
Gauge |
The chunk size for an arena (when |
reactor.netty.bytebuf.allocator.active.heap.buffers |
Gauge |
The actual bytes consumed by in-use heap buffers (when |
reactor.netty.bytebuf.allocator.active.direct.buffers |
Gauge |
The actual bytes consumed by in-use direct buffers (when |
EventLoop
metrics
metric name | type | description |
---|---|---|
reactor.netty.eventloop.pending.tasks |
Gauge |
The number of tasks that are pending for processing on an event loop |
The following example enables that integration:
import reactor.netty.Connection;
import reactor.netty.tcp.TcpClient;
public class Application {
public static void main(String[] args) {
Connection connection =
TcpClient.create()
.host("example.com")
.port(80)
.metrics(true) (1)
.connectNow();
connection.onDispose()
.block();
}
}
1 | Enables the built-in integration with Micrometer |
When TCP client metrics are needed for an integration with a system other than Micrometer
or you want
to provide your own integration with Micrometer
, you can provide your own metrics recorder, as follows:
import reactor.netty.Connection;
import reactor.netty.channel.ChannelMetricsRecorder;
import reactor.netty.tcp.TcpClient;
import java.net.SocketAddress;
import java.time.Duration;
public class Application {
public static void main(String[] args) {
Connection connection =
TcpClient.create()
.host("example.com")
.port(80)
.metrics(true, CustomChannelMetricsRecorder::new) (1)
.connectNow();
connection.onDispose()
.block();
}
1 | Enables TCP client metrics and provides ChannelMetricsRecorder implementation. |
4.11. Unix Domain Sockets
The TCP
client supports Unix Domain Sockets (UDS) when native transport is in use.
The following example shows how to use UDS support:
import io.netty.channel.unix.DomainSocketAddress;
import reactor.netty.Connection;
import reactor.netty.tcp.TcpClient;
public class Application {
public static void main(String[] args) {
Connection connection =
TcpClient.create()
.remoteAddress(() -> new DomainSocketAddress("/tmp/test.sock")) (1)
.connectNow();
connection.onDispose()
.block();
}
}
1 | Specifies DomainSocketAddress that will be used |
4.12. Host Name Resolution
By default, the TcpClient
uses Netty’s domain name lookup mechanism that resolves a domain name asynchronously.
This is as an alternative of the JVM’s built-in blocking resolver.
When you need to change the default settings, you can configure the TcpClient
as follows:
import reactor.netty.Connection;
import reactor.netty.tcp.TcpClient;
import java.time.Duration;
public class Application {
public static void main(String[] args) {
Connection connection =
TcpClient.create()
.host("example.com")
.port(80)
.resolver(spec -> spec.queryTimeout(Duration.ofMillis(500))) (1)
.connectNow();
connection.onDispose()
.block();
}
}
1 | The timeout of each DNS query performed by this resolver will be 500ms. |
The following listing shows the available configurations:
Configuration name | Description |
---|---|
|
The max time to live of the cached DNS resource records (resolution: seconds).
If the time to live of the DNS resource record returned by the DNS server is greater
than this max time to live, this resolver ignores the time to live from
the DNS server and uses use this max time to live.
Default to |
|
The min time to live of the cached DNS resource records (resolution: seconds). If the time to live of the DNS resource record returned by the DNS server is less than this min time to live, this resolver ignores the time to live from the DNS server and uses this min time to live. Default: 0. |
|
The time to live of the cache for the failed DNS queries (resolution: seconds). Default: 0. |
|
When this setting is enabled, the resolver notifies as soon as all queries for the preferred address type are complete.
When this setting is disabled, the resolver notifies when all possible address types are complete.
This configuration is applicable for |
|
Disables the automatic inclusion of an optional record that tries to give a hint to the remote DNS server about how much data the resolver can read per response. By default, this setting is enabled. |
|
Specifies whether this resolver has to send a DNS query with the recursion desired (RD) flag set. By default, this setting is enabled. |
|
Sets a custom |
|
Sets the capacity of the datagram packet buffer (in bytes). Default: 4096. |
|
Sets the maximum allowed number of DNS queries to send when resolving a host name. Default: 16. |
|
Sets the number of dots that must appear in a name before an initial absolute query is made. Default: -1 (to determine the value from the OS on Unix or use a value of 1 otherwise). |
|
Sets the timeout of each DNS query performed by this resolver (resolution: milliseconds). Default: 5000. |
|
The list of the protocol families of the resolved address. |
|
The supplier of the local address to bind to. |
|
Enables an
|
|
Performs the communication with the DNS servers on the given
|
|
The list of search domains of the resolver. By default, the effective search domain list is populated by using the system DNS search domains. |
|
A specific logger and log level to be used by this resolver when generating detailed trace information in case of resolution failure. |
Sometimes, you may want to switch to the JVM built-in resolver. To do so, you can configure the TcpClient
as follows:
import io.netty.resolver.DefaultAddressResolverGroup;
import reactor.netty.Connection;
import reactor.netty.tcp.TcpClient;
public class Application {
public static void main(String[] args) {
Connection connection =
TcpClient.create()
.host("example.com")
.port(80)
.resolver(DefaultAddressResolverGroup.INSTANCE) (1)
.connectNow();
connection.onDispose()
.block();
}
}
1 | Sets the JVM built-in resolver. |
Suggest Edit to "TCP Client"
5. HTTP Server
Reactor Netty
provides the easy-to-use and easy-to-configure
HttpServer
class.
It hides most of the Netty
functionality that is needed in order to create a HTTP
server
and adds Reactive Streams
backpressure.
5.1. Starting and Stopping
To start an HTTP server, you must create and configure a
HttpServer instance.
By default, the host
is configured for any local address, and the system picks up an ephemeral port
when the bind
operation is invoked.
The following example shows how to create an HttpServer
instance:
import reactor.netty.DisposableServer;
import reactor.netty.http.server.HttpServer;
public class Application {
public static void main(String[] args) {
DisposableServer server =
HttpServer.create() (1)
.bindNow(); (2)
server.onDispose()
.block();
}
}
1 | Creates an HttpServer instance ready for configuring. |
2 | Starts the server in a blocking fashion and waits for it to finish initializing. |
The returned DisposableServer
offers a simple server API, including disposeNow()
,
which shuts the server down in a blocking fashion.
5.1.1. Host and Port
To serve on a specific host
and port
, you can apply the following configuration to the HTTP
server:
import reactor.netty.DisposableServer;
import reactor.netty.http.server.HttpServer;
public class Application {
public static void main(String[] args) {
DisposableServer server =
HttpServer.create()
.host("localhost") (1)
.port(8080) (2)
.bindNow();
server.onDispose()
.block();
}
}
1 | Configures the HTTP server host |
2 | Configures the HTTP server port |
To serve on multiple addresses, after having configured the HttpServer
you can bind it multiple times to obtain separate DisposableServer`s.
All created servers will share resources such as `LoopResources
because they use the same configuration instance under the hood.
import reactor.core.publisher.Mono;
import reactor.netty.DisposableServer;
import reactor.netty.http.server.HttpServer;
public class MultiAddressApplication {
public static void main(String[] args) {
HttpServer httpServer = HttpServer.create();
DisposableServer server1 = httpServer
.host("localhost") (1)
.port(8080) (2)
.bindNow();
DisposableServer server2 = httpServer
.host("0.0.0.0") (3)
.port(8081) (4)
.bindNow();
Mono.when(server1.onDispose(), server2.onDispose())
.block();
}
}
1 | Configures the first HTTP server host |
2 | Configures the first HTTP server port |
3 | Configures the second HTTP server host |
4 | Configures the second HTTP server port |
5.2. Eager Initialization
By default, the initialization of the HttpServer
resources happens on demand. This means that the bind
operation
absorbs the extra time needed to initialize and load:
-
the event loop groups
-
the native transport libraries (when native transport is used)
-
the native libraries for the security (in case of
OpenSsl
)
When you need to preload these resources, you can configure the HttpServer
as follows:
import reactor.netty.DisposableServer;
import reactor.netty.http.server.HttpServer;
public class Application {
public static void main(String[] args) {
HttpServer httpServer =
HttpServer.create()
.handle((request, response) -> request.receive().then());
httpServer.warmup() (1)
.block();
DisposableServer server = httpServer.bindNow();
server.onDispose()
.block();
}
}
1 | Initialize and load the event loop groups, the native transport libraries and the native libraries for the security |
5.3. Routing HTTP
Defining routes for the HTTP
server requires configuring the provided
HttpServerRoutes
builder.
The following example shows how to do so:
import reactor.core.publisher.Mono;
import reactor.netty.DisposableServer;
import reactor.netty.http.server.HttpServer;
public class Application {
public static void main(String[] args) {
DisposableServer server =
HttpServer.create()
.route(routes ->
routes.get("/hello", (1)
(request, response) -> response.sendString(Mono.just("Hello World!")))
.post("/echo", (2)
(request, response) -> response.send(request.receive().retain()))
.get("/path/{param}", (3)
(request, response) -> response.sendString(Mono.just(request.param("param"))))
.ws("/ws", (4)
(wsInbound, wsOutbound) -> wsOutbound.send(wsInbound.receive().retain())))
.bindNow();
server.onDispose()
.block();
}
}
1 | Serves a GET request to /hello and returns Hello World! |
2 | Serves a POST request to /echo and returns the received request body as a response. |
3 | Serves a GET request to /path/{param} and returns the value of the path parameter. |
4 | Serves websocket to /ws and returns the received incoming data as outgoing data. |
The server routes are unique and only the first matching in order of declaration is invoked. |
5.3.1. SSE
The following code shows how you can configure the HTTP
server to serve Server-Sent Events
:
import com.fasterxml.jackson.databind.ObjectMapper;
import io.netty.buffer.ByteBuf;
import io.netty.buffer.ByteBufAllocator;
import org.reactivestreams.Publisher;
import reactor.core.publisher.Flux;
import reactor.netty.DisposableServer;
import reactor.netty.http.server.HttpServer;
import reactor.netty.http.server.HttpServerRequest;
import reactor.netty.http.server.HttpServerResponse;
import java.io.ByteArrayOutputStream;
import java.nio.charset.Charset;
import java.time.Duration;
import java.util.function.BiFunction;
public class Application {
public static void main(String[] args) {
DisposableServer server =
HttpServer.create()
.route(routes -> routes.get("/sse", serveSse()))
.bindNow();
server.onDispose()
.block();
}
/**
* Prepares SSE response
* The "Content-Type" is "text/event-stream"
* The flushing strategy is "flush after every element" emitted by the provided Publisher
*/
private static BiFunction<HttpServerRequest, HttpServerResponse, Publisher<Void>> serveSse() {
Flux<Long> flux = Flux.interval(Duration.ofSeconds(10));
return (request, response) ->
response.sse()
.send(flux.map(Application::toByteBuf), b -> true);
}
/**
* Transforms the Object to ByteBuf following the expected SSE format.
*/
private static ByteBuf toByteBuf(Object any) {
ByteArrayOutputStream out = new ByteArrayOutputStream();
try {
out.write("data: ".getBytes(Charset.defaultCharset()));
MAPPER.writeValue(out, any);
out.write("\n\n".getBytes(Charset.defaultCharset()));
}
catch (Exception e) {
throw new RuntimeException(e);
}
return ByteBufAllocator.DEFAULT
.buffer()
.writeBytes(out.toByteArray());
}
private static final ObjectMapper MAPPER = new ObjectMapper();
}
5.3.2. Static Resources
The following code shows how you can configure the HTTP
server to serve static resources:
import reactor.netty.DisposableServer;
import reactor.netty.http.server.HttpServer;
import java.net.URISyntaxException;
import java.nio.file.Path;
import java.nio.file.Paths;
public class Application {
public static void main(String[] args) throws URISyntaxException {
Path file = Paths.get(Application.class.getResource("/logback.xml").toURI());
DisposableServer server =
HttpServer.create()
.route(routes -> routes.file("/index.html", file))
.bindNow();
server.onDispose()
.block();
}
}
5.4. Writing Data
To send data to a connected client, you must attach an I/O handler by using either
handle(…)
or
route(…)
.
The I/O handler has access to HttpServerResponse
,
to be able to write data. The following example uses the handle(…)
method:
import reactor.core.publisher.Mono;
import reactor.netty.DisposableServer;
import reactor.netty.http.server.HttpServer;
public class Application {
public static void main(String[] args) {
DisposableServer server =
HttpServer.create()
.handle((request, response) -> response.sendString(Mono.just("hello"))) (1)
.bindNow();
server.onDispose()
.block();
}
}
1 | Sends hello string to the connected clients |
5.4.1. Adding Headers and Other Metadata
When you send data to the connected clients, you may need to send additional headers,
cookies, status code, and other metadata.
You can provide this additional metadata by using
HttpServerResponse
.
The following example shows how to do so:
import io.netty.handler.codec.http.HttpHeaderNames;
import io.netty.handler.codec.http.HttpResponseStatus;
import reactor.core.publisher.Mono;
import reactor.netty.DisposableServer;
import reactor.netty.http.server.HttpServer;
public class Application {
public static void main(String[] args) {
DisposableServer server =
HttpServer.create()
.route(routes ->
routes.get("/hello",
(request, response) ->
response.status(HttpResponseStatus.OK)
.header(HttpHeaderNames.CONTENT_LENGTH, "12")
.sendString(Mono.just("Hello World!"))))
.bindNow();
server.onDispose()
.block();
}
}
5.4.2. Compression
You can configure the HTTP
server to send a compressed response, depending on the request header
Accept-Encoding
.
Reactor Netty
provides three different strategies for compressing the outgoing data:
-
compress(boolean)
: Depending on the boolean that is provided, the compression is enabled (true
) or disabled (false
). -
compress(int)
: The compression is performed once the response size exceeds the given value (in bytes). -
compress(BiPredicate<HttpServerRequest, HttpServerResponse>)
: The compression is performed if the predicate returnstrue
.
The following example uses the compress
method (set to true
) to enable compression:
import reactor.netty.DisposableServer;
import reactor.netty.http.server.HttpServer;
import java.net.URISyntaxException;
import java.nio.file.Path;
import java.nio.file.Paths;
public class Application {
public static void main(String[] args) throws URISyntaxException {
Path file = Paths.get(Application.class.getResource("/logback.xml").toURI());
DisposableServer server =
HttpServer.create()
.compress(true)
.route(routes -> routes.file("/index.html", file))
.bindNow();
server.onDispose()
.block();
}
}
5.5. Consuming Data
To receive data from a connected client, you must attach an I/O handler by using either
handle(…)
or
route(…)
.
The I/O handler has access to HttpServerRequest
,
to be able to read data.
The following example uses the handle(…)
method:
import reactor.netty.DisposableServer;
import reactor.netty.http.server.HttpServer;
public class Application {
public static void main(String[] args) {
DisposableServer server =
HttpServer.create()
.handle((request, response) -> request.receive().then()) (1)
.bindNow();
server.onDispose()
.block();
}
}
1 | Receives data from the connected clients |
5.5.1. Reading Headers, URI Params, and other Metadata
When you receive data from the connected clients, you might need to check request headers,
parameters, and other metadata. You can obtain this additional metadata by using
HttpServerRequest
.
The following example shows how to do so:
import reactor.core.publisher.Mono;
import reactor.netty.DisposableServer;
import reactor.netty.http.server.HttpServer;
public class Application {
public static void main(String[] args) {
DisposableServer server =
HttpServer.create()
.route(routes ->
routes.get("/{param}",
(request, response) -> {
if (request.requestHeaders().contains("Some-Header")) {
return response.sendString(Mono.just(request.param("param")));
}
return response.sendNotFound();
}))
.bindNow();
server.onDispose()
.block();
}
}
5.5.2. Reading Post Form or Multipart Data
When you receive data from the connected clients, you might want to access POST
form
(application/x-www-form-urlencoded
) or
multipart
(multipart/form-data
) data. You can obtain this data by using
HttpServerRequest
.
import reactor.core.publisher.Mono;
import reactor.netty.DisposableServer;
import reactor.netty.http.server.HttpServer;
public class Application {
public static void main(String[] args) {
DisposableServer server =
HttpServer.create()
.route(routes ->
routes.post("/multipart", (request, response) -> response.sendString(
request.receiveForm() (1)
.flatMap(data -> Mono.just('[' + data.getName() + ']')))))
.bindNow();
server.onDispose()
.block();
}
}
1 | Receives POST form/multipart data. |
When you need to change the default settings, you can configure the HttpServer
or you can provide a configuration per request:
import reactor.core.publisher.Mono;
import reactor.netty.DisposableServer;
import reactor.netty.http.server.HttpServer;
public class Application {
public static void main(String[] args) {
DisposableServer server =
HttpServer.create()
.httpFormDecoder(builder -> builder.maxInMemorySize(0)) (1)
.route(routes ->
routes.post("/multipart", (request, response) -> response.sendString(
request.receiveForm(builder -> builder.maxInMemorySize(256)) (2)
.flatMap(data -> Mono.just('[' + data.getName() + ']')))))
.bindNow();
server.onDispose()
.block();
}
}
1 | Configuration on the HttpServer that specifies that the data is stored on disk only. |
2 | Configuration per request that specifies that if the data size exceed the specified size, the data is stored on the disk. |
The following listing shows the available configurations:
Configuration name | Description |
---|---|
|
Configures the directory where to store the data on the disk. Default to generated temp directory. |
|
Configures the |
|
Configures the maximum in-memory size per data i.e. the data is written
on disk if the size is greater than |
|
Configures the maximum size per data. When the limit is reached, an exception is raised.
If set to |
|
Configures the scheduler to be used for offloading disk operations in the decoding phase.
Default to |
|
When set to |
Obtaining the Remote (Client) Address
In addition to the metadata that you can obtain from the request, you can also receive the
host (server)
address, the remote (client)
address and the scheme
. Depending on the
chosen factory method, you can retrieve the information directly from the channel or by
using the Forwarded
or X-Forwarded-*
HTTP
request headers.
The following example shows how to do so:
import reactor.core.publisher.Mono;
import reactor.netty.DisposableServer;
import reactor.netty.http.server.HttpServer;
public class Application {
public static void main(String[] args) {
DisposableServer server =
HttpServer.create()
.forwarded(true) (1)
.route(routes ->
routes.get("/clientip",
(request, response) ->
response.sendString(Mono.just(request.remoteAddress() (2)
.getHostString()))))
.bindNow();
server.onDispose()
.block();
}
}
1 | Specifies that the information about the connection is to be obtained from the Forwarded and X-Forwarded-*
HTTP request headers, if possible. |
2 | Returns the address of the remote (client) peer. |
It is also possible to customize the behavior of the Forwarded
or X-Forwarded-*
header handler.
The following example shows how to do so:
import java.net.InetSocketAddress;
import reactor.core.publisher.Mono;
import reactor.netty.DisposableServer;
import reactor.netty.http.server.HttpServer;
import reactor.netty.transport.AddressUtils;
public class CustomForwardedHeaderHandlerApplication {
public static void main(String[] args) {
DisposableServer server =
HttpServer.create()
.forwarded((connectionInfo, request) -> { (1)
String hostHeader = request.headers().get("X-Forwarded-Host");
if (hostHeader != null) {
String[] hosts = hostHeader.split(",", 2);
InetSocketAddress hostAddress = AddressUtils.createUnresolved(
hosts[hosts.length - 1].trim(),
connectionInfo.getHostAddress().getPort());
connectionInfo = connectionInfo.withHostAddress(hostAddress);
}
return connectionInfo;
})
.route(routes ->
routes.get("/clientip",
(request, response) ->
response.sendString(Mono.just(request.remoteAddress() (2)
.getHostString()))))
.bindNow();
server.onDispose()
.block();
}
}
1 | Add a custom header handler. |
2 | Returns the address of the remote (client) peer. |
5.5.3. HTTP Request Decoder
By default, Netty
configures some restrictions for the incoming requests, such as:
-
The maximum length of the initial line.
-
The maximum length of all headers.
-
The maximum length of the content or each chunk.
For more information, see HttpRequestDecoder
and HttpServerUpgradeHandler
By default, the HTTP
server is configured with the following settings:
public static final int DEFAULT_MAX_INITIAL_LINE_LENGTH = 4096;
public static final int DEFAULT_MAX_HEADER_SIZE = 8192;
public static final int DEFAULT_MAX_CHUNK_SIZE = 8192;
public static final boolean DEFAULT_VALIDATE_HEADERS = true;
public static final int DEFAULT_INITIAL_BUFFER_SIZE = 128;
public static final boolean DEFAULT_ALLOW_DUPLICATE_CONTENT_LENGTHS = false;
/**
* The maximum length of the content of the HTTP/2.0 clear-text upgrade request.
* By default, the server will reject an upgrade request with non-empty content,
* because the upgrade request is most likely a GET request.
*/
public static final int DEFAULT_H2C_MAX_CONTENT_LENGTH = 0;
When you need to change these default settings, you can configure the HTTP
server as follows:
import reactor.core.publisher.Mono;
import reactor.netty.DisposableServer;
import reactor.netty.http.server.HttpServer;
public class Application {
public static void main(String[] args) {
DisposableServer server =
HttpServer.create()
.httpRequestDecoder(spec -> spec.maxHeaderSize(16384)) (1)
.handle((request, response) -> response.sendString(Mono.just("hello")))
.bindNow();
server.onDispose()
.block();
}
}
1 | The maximum length of all headers will be 16384 .
When this value is exceeded, a
TooLongFrameException
is raised. |
5.6. Lifecycle Callbacks
The following lifecycle callbacks are provided to let you extend the HttpServer
:
Callback | Description |
---|---|
|
Invoked when the server channel is about to bind. |
|
Invoked when the server channel is bound. |
|
Invoked when initializing the channel. |
|
Invoked when a remote client is connected |
|
Invoked when the server channel is unbound. |
The following example uses the doOnConnection
and doOnChannelInit
callbacks:
import io.netty.handler.logging.LoggingHandler;
import io.netty.handler.timeout.ReadTimeoutHandler;
import reactor.netty.DisposableServer;
import reactor.netty.http.server.HttpServer;
import java.util.concurrent.TimeUnit;
public class Application {
public static void main(String[] args) {
DisposableServer server =
HttpServer.create()
.doOnConnection(conn ->
conn.addHandlerFirst(new ReadTimeoutHandler(10, TimeUnit.SECONDS))) (1)
.doOnChannelInit((observer, channel, remoteAddress) ->
channel.pipeline()
.addFirst(new LoggingHandler("reactor.netty.examples"))) (2)
.bindNow();
server.onDispose()
.block();
}
}
1 | Netty pipeline is extended with ReadTimeoutHandler when a remote client is connected. |
2 | Netty pipeline is extended with LoggingHandler when initializing the channel. |
5.7. TCP-level Configuration
When you need to change configuration on the TCP level, you can use the following snippet
to extend the default TCP
server configuration:
import io.netty.channel.ChannelOption;
import reactor.netty.DisposableServer;
import reactor.netty.http.server.HttpServer;
public class Application {
public static void main(String[] args) {
DisposableServer server =
HttpServer.create()
.option(ChannelOption.CONNECT_TIMEOUT_MILLIS, 10000)
.bindNow();
server.onDispose()
.block();
}
}
See TCP Server for more detail about TCP-level configuration.
5.7.1. Wire Logger
Reactor Netty provides wire logging for when the traffic between the peers needs to be inspected.
By default, wire logging is disabled.
To enable it, you must set the logger reactor.netty.http.server.HttpServer
level to DEBUG
and apply the following configuration:
import reactor.netty.DisposableServer;
import reactor.netty.http.server.HttpServer;
public class Application {
public static void main(String[] args) {
DisposableServer server =
HttpServer.create()
.wiretap(true) (1)
.bindNow();
server.onDispose()
.block();
}
}
1 | Enables the wire logging |
Wire Logger formatters
Reactor Netty supports 3 different formatters:
-
AdvancedByteBufFormat#HEX_DUMP - the default
/**
* When wire logging is enabled with this format, both events and content will be logged.
* The content will be in hex format.
* <p>Examples:</p>
* <pre>
* {@code
* reactor.netty.http.HttpTests - [d5230a14, L:/0:0:0:0:0:0:0:1:60267 - R:/0:0:0:0:0:0:0:1:60269] REGISTERED
* reactor.netty.http.HttpTests - [d5230a14, L:/0:0:0:0:0:0:0:1:60267 - R:/0:0:0:0:0:0:0:1:60269] ACTIVE
* reactor.netty.http.HttpTests - [d5230a14, L:/0:0:0:0:0:0:0:1:60267 - R:/0:0:0:0:0:0:0:1:60269] READ: 145B
* +-------------------------------------------------+
* | 0 1 2 3 4 5 6 7 8 9 a b c d e f |
* +--------+-------------------------------------------------+----------------+
* |00000000| 50 4f 53 54 20 2f 74 65 73 74 2f 57 6f 72 6c 64 |POST /test/World|
* |00000010| 20 48 54 54 50 2f 31 2e 31 0d 0a 43 6f 6e 74 65 | HTTP/1.1..Conte|
* |00000020| 6e 74 2d 54 79 70 65 3a 20 74 65 78 74 2f 70 6c |nt-Type: text/pl|
* |00000030| 61 69 6e 0d 0a 75 73 65 72 2d 61 67 65 6e 74 3a |ain..user-agent:|
* |00000040| 20 52 65 61 63 74 6f 72 4e 65 74 74 79 2f 64 65 | ReactorNetty/de|
* ...
* reactor.netty.http.HttpTests - [d5230a14, L:/0:0:0:0:0:0:0:1:60267 - R:/0:0:0:0:0:0:0:1:60269] WRITE: 38B
* +-------------------------------------------------+
* | 0 1 2 3 4 5 6 7 8 9 a b c d e f |
* +--------+-------------------------------------------------+----------------+
* |00000000| 48 54 54 50 2f 31 2e 31 20 32 30 30 20 4f 4b 0d |HTTP/1.1 200 OK.|
* |00000010| 0a 63 6f 6e 74 65 6e 74 2d 6c 65 6e 67 74 68 3a |.content-length:|
* |00000020| 20 30 0d 0a 0d 0a | 0.... |
* +--------+-------------------------------------------------+----------------+
* }
* </pre>
*/
/**
* When wire logging is enabled with this format, only the events will be logged.
* <p>Examples:</p>
* <pre>
* {@code
* reactor.netty.http.HttpTests - [230d3686, L:/0:0:0:0:0:0:0:1:60241 - R:/0:0:0:0:0:0:0:1:60245] REGISTERED
* reactor.netty.http.HttpTests - [230d3686, L:/0:0:0:0:0:0:0:1:60241 - R:/0:0:0:0:0:0:0:1:60245] ACTIVE
* reactor.netty.http.HttpTests - [230d3686, L:/0:0:0:0:0:0:0:1:60241 - R:/0:0:0:0:0:0:0:1:60245] READ: 145B
* reactor.netty.http.HttpTests - [230d3686, L:/0:0:0:0:0:0:0:1:60241 - R:/0:0:0:0:0:0:0:1:60245] WRITE: 38B
* }
* </pre>
*/
/**
* When wire logging is enabled with this format, both events and content will be logged.
* The content will be in plain text format.
* <p>Examples:</p>
* <pre>
* {@code
* reactor.netty.http.HttpTests - [02c3db6c, L:/0:0:0:0:0:0:0:1:60317 - R:/0:0:0:0:0:0:0:1:60319] REGISTERED
* reactor.netty.http.HttpTests - [02c3db6c, L:/0:0:0:0:0:0:0:1:60317 - R:/0:0:0:0:0:0:0:1:60319] ACTIVE
* reactor.netty.http.HttpTests - [02c3db6c, L:/0:0:0:0:0:0:0:1:60317 - R:/0:0:0:0:0:0:0:1:60319] READ: 145B POST /test/World HTTP/1.1
* Content-Type: text/plain
* user-agent: ReactorNetty/dev
* ...
* reactor.netty.http.HttpTests - [02c3db6c, L:/0:0:0:0:0:0:0:1:60317 - R:/0:0:0:0:0:0:0:1:60319] WRITE: 38B HTTP/1.1 200 OK
* content-length: 0
* }
* </pre>
*/
When you need to change the default formatter you can configure it as follows:
import io.netty.handler.logging.LogLevel;
import reactor.netty.DisposableServer;
import reactor.netty.http.server.HttpServer;
import reactor.netty.transport.logging.AdvancedByteBufFormat;
public class Application {
public static void main(String[] args) {
DisposableServer server =
HttpServer.create()
.wiretap("logger-name", LogLevel.DEBUG, AdvancedByteBufFormat.TEXTUAL) (1)
.bindNow();
server.onDispose()
.block();
}
}
1 | Enables the wire logging, AdvancedByteBufFormat#TEXTUAL is used for printing the content. |
5.8. SSL and TLS
When you need SSL or TLS, you can apply the configuration shown in the next example.
By default, if OpenSSL
is available,
SslProvider.OPENSSL
provider is used as a provider. Otherwise
SslProvider.JDK
is used.
You can switch the provider by using
SslContextBuilder
or by setting -Dio.netty.handler.ssl.noOpenSsl=true
.
The following example uses SslContextBuilder
:
import reactor.netty.DisposableServer;
import reactor.netty.http.Http11SslContextSpec;
import reactor.netty.http.server.HttpServer;
import java.io.File;
public class Application {
public static void main(String[] args) {
File cert = new File("certificate.crt");
File key = new File("private.key");
Http11SslContextSpec http11SslContextSpec = Http11SslContextSpec.forServer(cert, key);
DisposableServer server =
HttpServer.create()
.secure(spec -> spec.sslContext(http11SslContextSpec))
.bindNow();
server.onDispose()
.block();
}
}
5.8.1. Server Name Indication
You can configure the HTTP
server with multiple SslContext
mapped to a specific domain.
An exact domain name or a domain name containing a wildcard can be used when configuring the SNI
mapping.
The following example uses a domain name containing a wildcard:
import io.netty.handler.ssl.SslContext;
import io.netty.handler.ssl.SslContextBuilder;
import reactor.netty.DisposableServer;
import reactor.netty.http.server.HttpServer;
import java.io.File;
public class Application {
public static void main(String[] args) throws Exception {
File defaultCert = new File("default_certificate.crt");
File defaultKey = new File("default_private.key");
File testDomainCert = new File("default_certificate.crt");
File testDomainKey = new File("default_private.key");
SslContext defaultSslContext = SslContextBuilder.forServer(defaultCert, defaultKey).build();
SslContext testDomainSslContext = SslContextBuilder.forServer(testDomainCert, testDomainKey).build();
DisposableServer server =
HttpServer.create()
.secure(spec -> spec.sslContext(defaultSslContext)
.addSniMapping("*.test.com",
testDomainSpec -> testDomainSpec.sslContext(testDomainSslContext)))
.bindNow();
server.onDispose()
.block();
}
}
5.9. HTTP Access Log
You can enable the HTTP
access log either programmatically or by configuration. By default, it is disabled.
You can use -Dreactor.netty.http.server.accessLogEnabled=true
to enable the HTTP
access log by configuration.
You can use the following configuration (for Logback or similar logging frameworks) to have a separate
HTTP
access log file:
<appender name="accessLog" class="ch.qos.logback.core.FileAppender">
<file>access_log.log</file>
<encoder>
<pattern>%msg%n</pattern>
</encoder>
</appender>
<appender name="async" class="ch.qos.logback.classic.AsyncAppender">
<appender-ref ref="accessLog" />
</appender>
<logger name="reactor.netty.http.server.AccessLog" level="INFO" additivity="false">
<appender-ref ref="async"/>
</logger>
The following example enables it programmatically:
import reactor.netty.DisposableServer;
import reactor.netty.http.server.HttpServer;
public class Application {
public static void main(String[] args) {
DisposableServer server =
HttpServer.create()
.accessLog(true)
.bindNow();
server.onDispose()
.block();
}
}
Calling this method takes precedence over the system property configuration.
By default, the logging format is Common Log Format, but you can specify a custom one as a parameter, as in the following example:
import reactor.netty.DisposableServer;
import reactor.netty.http.server.HttpServer;
import reactor.netty.http.server.logging.AccessLog;
public class CustomLogAccessFormatApplication {
public static void main(String[] args) {
DisposableServer server =
HttpServer.create()
.accessLog(true, x -> AccessLog.create("method={}, uri={}", x.method(), x.uri()))
.bindNow();
server.onDispose()
.block();
}
}
You can also filter HTTP
access logs by using the AccessLogFactory#createFilter
method, as in the following example:
import reactor.netty.DisposableServer;
import reactor.netty.http.server.HttpServer;
import reactor.netty.http.server.logging.AccessLogFactory;
public class FilterLogAccessApplication {
public static void main(String[] args) {
DisposableServer server =
HttpServer.create()
.accessLog(true, AccessLogFactory.createFilter(p -> !String.valueOf(p.uri()).startsWith("/health/")))
.bindNow();
server.onDispose()
.block();
}
}
Note that this method can take a custom format parameter too, as in this example:
import reactor.netty.DisposableServer;
import reactor.netty.http.server.HttpServer;
import reactor.netty.http.server.logging.AccessLog;
import reactor.netty.http.server.logging.AccessLogFactory;
public class CustomFormatAndFilterAccessLogApplication {
public static void main(String[] args) {
DisposableServer server =
HttpServer.create()
.accessLog(true, AccessLogFactory.createFilter(p -> !String.valueOf(p.uri()).startsWith("/health/"), (1)
x -> AccessLog.create("method={}, uri={}", x.method(), x.uri()))) (2)
.bindNow();
server.onDispose()
.block();
}
}
1 | Specifies the filter predicate to use |
2 | Specifies the custom format to apply |
5.10. HTTP/2
By default, the HTTP
server supports HTTP/1.1
. If you need HTTP/2
, you can get it through configuration.
In addition to the protocol configuration, if you need H2
but not H2C (cleartext)
, you must also configure SSL.
As Application-Layer Protocol Negotiation (ALPN) is not supported “out-of-the-box” by JDK8 (although some vendors backported ALPN to JDK8), you need an additional dependency to a native library that
supports it — for example, netty-tcnative-boringssl-static .
|
The following listing presents a simple H2
example:
import reactor.core.publisher.Mono;
import reactor.netty.DisposableServer;
import reactor.netty.http.Http2SslContextSpec;
import reactor.netty.http.HttpProtocol;
import reactor.netty.http.server.HttpServer;
import java.io.File;
public class H2Application {
public static void main(String[] args) {
File cert = new File("certificate.crt");
File key = new File("private.key");
Http2SslContextSpec http2SslContextSpec = Http2SslContextSpec.forServer(cert, key);
DisposableServer server =
HttpServer.create()
.port(8080)
.protocol(HttpProtocol.H2) (1)
.secure(spec -> spec.sslContext(http2SslContextSpec)) (2)
.handle((request, response) -> response.sendString(Mono.just("hello")))
.bindNow();
server.onDispose()
.block();
}
}
1 | Configures the server to support only HTTP/2 |
2 | Configures SSL |
The application should now behave as follows:
$ curl --http2 https://localhost:8080 -i
HTTP/2 200
hello
The following listing presents a simple H2C
example:
import reactor.core.publisher.Mono;
import reactor.netty.DisposableServer;
import reactor.netty.http.HttpProtocol;
import reactor.netty.http.server.HttpServer;
public class H2CApplication {
public static void main(String[] args) {
DisposableServer server =
HttpServer.create()
.port(8080)
.protocol(HttpProtocol.H2C)
.handle((request, response) -> response.sendString(Mono.just("hello")))
.bindNow();
server.onDispose()
.block();
}
}
The application should now behave as follows:
$ curl --http2-prior-knowledge http://localhost:8080 -i
HTTP/2 200
hello
5.10.1. Protocol Selection
public enum HttpProtocol {
/**
* The default supported HTTP protocol by HttpServer and HttpClient
*/
HTTP11,
/**
* HTTP/2.0 support with TLS
* <p>If used along with HTTP/1.1 protocol, HTTP/2.0 will be the preferred protocol.
* While negotiating the application level protocol, HTTP/2.0 or HTTP/1.1 can be chosen.
* <p>If used without HTTP/1.1 protocol, HTTP/2.0 will always be offered as a protocol
* for communication with no fallback to HTTP/1.1.
*/
H2,
/**
* HTTP/2.0 support with clear-text.
* <p>If used along with HTTP/1.1 protocol, will support H2C "upgrade":
* Request or consume requests as HTTP/1.1 first, looking for HTTP/2.0 headers
* and {@literal Connection: Upgrade}. A server will typically reply a successful
* 101 status if upgrade is successful or a fallback HTTP/1.1 response. When
* successful the client will start sending HTTP/2.0 traffic.
* <p>If used without HTTP/1.1 protocol, will support H2C "prior-knowledge": Doesn't
* require {@literal Connection: Upgrade} handshake between a client and server but
* fallback to HTTP/1.1 will not be supported.
*/
H2C
}
5.11. Metrics
The HTTP server supports built-in integration with Micrometer
.
It exposes all metrics with a prefix of reactor.netty.http.server
.
The following table provides information for the HTTP server metrics:
metric name | type | description |
---|---|---|
reactor.netty.http.server.connections.active |
Gauge |
The number of http connections currently processing requests |
reactor.netty.http.server.connections.total |
Gauge |
The number of all opened connections |
reactor.netty.http.server.data.received |
DistributionSummary |
Amount of the data received, in bytes |
reactor.netty.http.server.data.sent |
DistributionSummary |
Amount of the data sent, in bytes |
reactor.netty.http.server.errors |
Counter |
Number of errors that occurred |
reactor.netty.http.server.data.received.time |
Timer |
Time spent in consuming incoming data |
reactor.netty.http.server.data.sent.time |
Timer |
Time spent in sending outgoing data |
reactor.netty.http.server.response.time |
Timer |
Total time for the request/response |
These additional metrics are also available:
ByteBufAllocator
metrics
metric name | type | description |
---|---|---|
reactor.netty.bytebuf.allocator.used.heap.memory |
Gauge |
The number of bytes reserved by heap buffer allocator |
reactor.netty.bytebuf.allocator.used.direct.memory |
Gauge |
The number of bytes reserved by direct buffer allocator |
reactor.netty.bytebuf.allocator.used.heap.arenas |
Gauge |
The number of heap arenas (when |
reactor.netty.bytebuf.allocator.used.direct.arenas |
Gauge |
The number of direct arenas (when |
reactor.netty.bytebuf.allocator.used.threadlocal.caches |
Gauge |
The number of thread local caches (when |
reactor.netty.bytebuf.allocator.used.small.cache.size |
Gauge |
The size of the small cache (when |
reactor.netty.bytebuf.allocator.used.normal.cache.size |
Gauge |
The size of the normal cache (when |
reactor.netty.bytebuf.allocator.used.chunk.size |
Gauge |
The chunk size for an arena (when |
reactor.netty.bytebuf.allocator.active.heap.buffers |
Gauge |
The actual bytes consumed by in-use heap buffers (when |
reactor.netty.bytebuf.allocator.active.direct.buffers |
Gauge |
The actual bytes consumed by in-use direct buffers (when |
EventLoop
metrics
metric name | type | description |
---|---|---|
reactor.netty.eventloop.pending.tasks |
Gauge |
The number of tasks that are pending for processing on an event loop |
The following example enables that integration:
import io.micrometer.core.instrument.Metrics;
import io.micrometer.core.instrument.config.MeterFilter;
import reactor.core.publisher.Mono;
import reactor.netty.DisposableServer;
import reactor.netty.http.server.HttpServer;
public class Application {
public static void main(String[] args) {
Metrics.globalRegistry (1)
.config()
.meterFilter(MeterFilter.maximumAllowableTags("reactor.netty.http.server", "URI", 100, MeterFilter.deny()));
DisposableServer server =
HttpServer.create()
.metrics(true, s -> {
if (s.startsWith("/stream/")) { (2)
return "/stream/{n}";
}
else if (s.startsWith("/bytes/")) {
return "/bytes/{n}";
}
return s;
}) (3)
.route(r ->
r.get("/stream/{n}",
(req, res) -> res.sendString(Mono.just(req.param("n"))))
.get("/bytes/{n}",
(req, res) -> res.sendString(Mono.just(req.param("n")))))
.bindNow();
server.onDispose()
.block();
}
}
1 | Applies upper limit for the meters with URI tag |
2 | Templated URIs will be used as an URI tag value when possible |
3 | Enables the built-in integration with Micrometer |
In order to avoid a memory and CPU overhead of the enabled metrics, it is important to convert the real URIs to templated URIs when possible. Without a conversion to a template-like form, each distinct URI leads to the creation of a distinct tag, which takes a lot of memory for the metrics. |
Always apply an upper limit for the meters with URI tags. Configuring an upper limit on the number of meters can help in cases when the real URIs cannot be templated.
You can find more information at maximumAllowableTags .
|
When HTTP server metrics are needed for an integration with a system other than Micrometer
or you want
to provide your own integration with Micrometer
, you can provide your own metrics recorder, as follows:
import reactor.core.publisher.Mono;
import reactor.netty.DisposableServer;
import reactor.netty.http.server.HttpServer;
import reactor.netty.http.server.HttpServerMetricsRecorder;
import java.net.SocketAddress;
import java.time.Duration;
public class Application {
public static void main(String[] args) {
DisposableServer server =
HttpServer.create()
.metrics(true, CustomHttpServerMetricsRecorder::new) (1)
.route(r ->
r.get("/stream/{n}",
(req, res) -> res.sendString(Mono.just(req.param("n"))))
.get("/bytes/{n}",
(req, res) -> res.sendString(Mono.just(req.param("n")))))
.bindNow();
server.onDispose()
.block();
}
1 | Enables HTTP server metrics and provides HttpServerMetricsRecorder implementation. |
5.12. Unix Domain Sockets
The HTTP
server supports Unix Domain Sockets (UDS) when native transport is in use.
The following example shows how to use UDS support:
import io.netty.channel.unix.DomainSocketAddress;
import reactor.netty.DisposableServer;
import reactor.netty.http.server.HttpServer;
public class Application {
public static void main(String[] args) {
DisposableServer server =
HttpServer.create()
.bindAddress(() -> new DomainSocketAddress("/tmp/test.sock")) (1)
.bindNow();
server.onDispose()
.block();
}
}
1 | Specifies DomainSocketAddress that will be used |
Suggest Edit to "HTTP Server"
6. HTTP Client
Reactor Netty provides the easy-to-use and easy-to-configure
HttpClient
.
It hides most of the Netty functionality that is required to create an HTTP
client
and adds Reactive Streams backpressure.
6.1. Connect
To connect the HTTP
client to a given HTTP
endpoint, you must create and configure a
HttpClient
instance.
The following example shows how to do so:
import reactor.netty.http.client.HttpClient;
public class Application {
public static void main(String[] args) {
HttpClient client = HttpClient.create(); (1)
client.get() (2)
.uri("https://example.com/") (3)
.response() (4)
.block();
}
}
1 | Creates a HttpClient instance ready for configuring. |
2 | Specifies that GET method will be used. |
3 | Specifies the path. |
4 | Obtains the response HttpClientResponse |
The following example uses WebSocket
:
import io.netty.buffer.Unpooled;
import io.netty.util.CharsetUtil;
import reactor.core.publisher.Flux;
import reactor.netty.http.client.HttpClient;
public class Application {
public static void main(String[] args) {
HttpClient client = HttpClient.create();
client.websocket()
.uri("wss://echo.websocket.org")
.handle((inbound, outbound) -> {
inbound.receive()
.asString()
.take(1)
.subscribe(System.out::println);
final byte[] msgBytes = "hello".getBytes(CharsetUtil.ISO_8859_1);
return outbound.send(Flux.just(Unpooled.wrappedBuffer(msgBytes), Unpooled.wrappedBuffer(msgBytes)))
.neverComplete();
})
.blockLast();
}
}
6.1.1. Host and Port
In order to connect to a specific host and port, you can apply the following configuration to the HTTP
client:
import reactor.netty.http.client.HttpClient;
public class Application {
public static void main(String[] args) {
HttpClient client =
HttpClient.create()
.host("example.com") (1)
.port(80); (2)
client.get()
.uri("/")
.response()
.block();
}
}
1 | Configures the HTTP host |
2 | Configures the HTTP port |
6.2. Eager Initialization
By default, the initialization of the HttpClient
resources happens on demand. This means that the first
request
absorbs the extra time needed to initialize and load:
-
the event loop group
-
the host name resolver
-
the native transport libraries (when native transport is used)
-
the native libraries for the security (in case of
OpenSsl
)
When you need to preload these resources, you can configure the HttpClient
as follows:
import reactor.core.publisher.Mono;
import reactor.netty.ByteBufFlux;
import reactor.netty.http.client.HttpClient;
public class Application {
public static void main(String[] args) {
HttpClient client = HttpClient.create();
client.warmup() (1)
.block();
client.post()
.uri("https://example.com/")
.send(ByteBufFlux.fromString(Mono.just("hello")))
.response()
.block(); (2)
}
}
1 | Initialize and load the event loop group, the host name resolver, the native transport libraries and the native libraries for the security |
2 | Host name resolution happens with the first request. In this example, a connection pool is used, so with the first request the connection to the URL is established, the subsequent requests to the same URL reuse the connections from the pool. |
6.3. Writing Data
To send data to a given HTTP
endpoint, you can provide a Publisher
by using the
send(Publisher)
method.
By default, Transfer-Encoding: chunked
is applied for those HTTP
methods for which
a request body is expected. Content-Length
provided through request headers disables Transfer-Encoding: chunked
,
if necessary. The following example sends hello
:
import reactor.core.publisher.Mono;
import reactor.netty.ByteBufFlux;
import reactor.netty.http.client.HttpClient;
public class Application {
public static void main(String[] args) {
HttpClient client = HttpClient.create();
client.post()
.uri("https://example.com/")
.send(ByteBufFlux.fromString(Mono.just("hello"))) (1)
.response()
.block();
}
}
1 | Sends a hello string to the given HTTP endpoint |
6.3.1. Adding Headers and Other Metadata
When sending data to a given HTTP
endpoint, you may need to send additional headers, cookies and other metadata.
You can use the following configuration to do so:
import io.netty.handler.codec.http.HttpHeaderNames;
import reactor.core.publisher.Mono;
import reactor.netty.ByteBufFlux;
import reactor.netty.http.client.HttpClient;
public class Application {
public static void main(String[] args) {
HttpClient client =
HttpClient.create()
.headers(h -> h.set(HttpHeaderNames.CONTENT_LENGTH, 5)); (1)
client.post()
.uri("https://example.com/")
.send(ByteBufFlux.fromString(Mono.just("hello")))
.response()
.block();
}
}
1 | Disables Transfer-Encoding: chunked and provides Content-Length header. |
Compression
You can enable compression on the HTTP
client, which means the request header
Accept-Encoding
is added to the request headers. The following example shows how to do so:
import reactor.netty.http.client.HttpClient;
public class Application {
public static void main(String[] args) {
HttpClient client =
HttpClient.create()
.compress(true);
client.get()
.uri("https://example.com/")
.response()
.block();
}
}
Auto-Redirect Support
You can configure the HTTP
client to enable auto-redirect support.
Reactor Netty provides two different strategies for auto-redirect support:
-
followRedirect(boolean)
: Specifies whether HTTP auto-redirect support is enabled for statuses301|302|307|308
. -
followRedirect(BiPredicate<HttpClientRequest, HttpClientResponse>)
: Enables auto-redirect support if the supplied predicate matches.
The following example uses followRedirect(true)
:
import reactor.netty.http.client.HttpClient;
public class Application {
public static void main(String[] args) {
HttpClient client =
HttpClient.create()
.followRedirect(true);
client.get()
.uri("https://example.com/")
.response()
.block();
}
}
6.4. Consuming Data
To receive data from a given HTTP
endpoint, you can use one of the methods from
HttpClient.ResponseReceiver
.
The following example uses the responseContent
method:
import reactor.netty.http.client.HttpClient;
public class Application {
public static void main(String[] args) {
HttpClient client = HttpClient.create();
client.get()
.uri("https://example.com/")
.responseContent() (1)
.aggregate() (2)
.asString() (3)
.block();
}
}
1 | Receives data from a given HTTP endpoint |
2 | Aggregates the data |
3 | Transforms the data as string |
6.4.1. Reading Headers and Other Metadata
When receiving data from a given HTTP
endpoint, you can check response headers, status code, and other metadata.
You can obtain this additional metadata by using
HttpClientResponse
.
The following example shows how to do so.
import reactor.netty.http.client.HttpClient;
public class Application {
public static void main(String[] args) {
HttpClient client = HttpClient.create();
client.get()
.uri("https://example.com/")
.responseSingle((resp, bytes) -> {
System.out.println(resp.status()); (1)
return bytes.asString();
})
.block();
}
}
1 | Obtains the status code. |
6.4.2. HTTP Response Decoder
By default, Netty
configures some restrictions for the incoming responses, such as:
-
The maximum length of the initial line.
-
The maximum length of all headers.
-
The maximum length of the content or each chunk.
For more information, see HttpResponseDecoder
By default, the HTTP
client is configured with the following settings:
public static final int DEFAULT_MAX_INITIAL_LINE_LENGTH = 4096;
public static final int DEFAULT_MAX_HEADER_SIZE = 8192;
public static final int DEFAULT_MAX_CHUNK_SIZE = 8192;
public static final boolean DEFAULT_VALIDATE_HEADERS = true;
public static final int DEFAULT_INITIAL_BUFFER_SIZE = 128;
public static final boolean DEFAULT_ALLOW_DUPLICATE_CONTENT_LENGTHS = false;
public static final boolean DEFAULT_FAIL_ON_MISSING_RESPONSE = false;
public static final boolean DEFAULT_PARSE_HTTP_AFTER_CONNECT_REQUEST = false;
/**
* The maximum length of the content of the HTTP/2.0 clear-text upgrade request.
* By default, the client will allow an upgrade request with up to 65536 as
* the maximum length of the aggregated content.
*/
public static final int DEFAULT_H2C_MAX_CONTENT_LENGTH = 65536;
When you need to change these default settings, you can configure the HTTP
client as follows:
import reactor.netty.http.client.HttpClient;
public class Application {
public static void main(String[] args) {
HttpClient client =
HttpClient.create()
.httpResponseDecoder(spec -> spec.maxHeaderSize(16384)); (1)
client.get()
.uri("https://example.com/")
.responseContent()
.aggregate()
.asString()
.block();
}
}
1 | The maximum length of all headers will be 16384 .
When this value is exceeded, a
TooLongFrameException
is raised. |
6.5. Lifecycle Callbacks
The following lifecycle callbacks are provided to let you extend the HttpClient
.
Callback | Description |
---|---|
|
Invoked when the request has been sent. |
|
Invoked after the remote address has been resolved successfully. |
|
Invoked after the response has been fully received. |
|
Invoked when initializing the channel. |
|
Invoked when the channel is about to connect. |
|
Invoked after the channel has been connected. |
|
Invoked after the channel has been disconnected. |
|
Invoked when the request has not been sent and when the response has not been fully received. |
|
Invoked when the response headers have been received, and the request is about to be redirected. |
|
Invoked when the request is about to be sent. |
|
Invoked when the request has not been sent. |
|
Invoked when the remote address is about to be resolved. |
|
Invoked in case the remote address hasn’t been resolved successfully. |
|
Invoked after the response headers have been received. |
|
Invoked when the response has not been fully received. |
The following example uses the doOnConnected
and doOnChannelInit
callbacks:
import io.netty.handler.logging.LoggingHandler;
import io.netty.handler.timeout.ReadTimeoutHandler;
import reactor.netty.http.client.HttpClient;
import java.util.concurrent.TimeUnit;
public class Application {
public static void main(String[] args) {
HttpClient client =
HttpClient.create()
.doOnConnected(conn ->
conn.addHandlerFirst(new ReadTimeoutHandler(10, TimeUnit.SECONDS))) (1)
.doOnChannelInit((observer, channel, remoteAddress) ->
channel.pipeline()
.addFirst(new LoggingHandler("reactor.netty.examples"))); (2)
client.get()
.uri("https://example.com/")
.response()
.block();
}
}
1 | Netty pipeline is extended with ReadTimeoutHandler when the channel has been connected. |
2 | Netty pipeline is extended with LoggingHandler when initializing the channel. |
6.6. TCP-level Configuration
When you need configurations on a TCP level, you can use the following snippet
to extend the default TCP
client configuration (add an option, bind address etc.):
import io.netty.channel.ChannelOption;
import io.netty.channel.epoll.EpollChannelOption;
//import io.netty.channel.socket.nio.NioChannelOption;
//import jdk.net.ExtendedSocketOptions;
import reactor.netty.http.client.HttpClient;
import java.net.InetSocketAddress;
public class Application {
public static void main(String[] args) {
HttpClient client =
HttpClient.create()
.bindAddress(() -> new InetSocketAddress("host", 1234))
.option(ChannelOption.CONNECT_TIMEOUT_MILLIS, 10000) (1)
.option(ChannelOption.SO_KEEPALIVE, true) (2)
// The options below are available only when NIO transport (Java 11) is used
// on Mac or Linux (Java does not currently support these extended options on Windows)
// https://bugs.openjdk.java.net/browse/JDK-8194298
//.option(NioChannelOption.of(ExtendedSocketOptions.TCP_KEEPIDLE), 300)
//.option(NioChannelOption.of(ExtendedSocketOptions.TCP_KEEPINTERVAL), 60)
//.option(NioChannelOption.of(ExtendedSocketOptions.TCP_KEEPCOUNT), 8);
// The options below are available only when Epoll transport is used
.option(EpollChannelOption.TCP_KEEPIDLE, 300) (3)
.option(EpollChannelOption.TCP_KEEPINTVL, 60) (4)
.option(EpollChannelOption.TCP_KEEPCNT, 8); (5)
String response =
client.get()
.uri("https://example.com/")
1 | Configures the connection establishment timeout to 10 seconds. |
2 | Enables TCP keepalive . This means that TCP starts sending keepalive probes when a connection is idle for some time. |
3 | The connection needs to remain idle for 5 minutes before TCP starts sending keepalive probes. |
4 | Configures the time between individual keepalive probes to 1 minute. |
5 | Configures the maximum number of TCP keepalive probes to 8. |
See TCP Client for more about TCP
level configurations.
6.6.1. Wire Logger
Reactor Netty provides wire logging for when the traffic between the peers needs to be inspected.
By default, wire logging is disabled.
To enable it, you must set the logger reactor.netty.http.client.HttpClient
level to DEBUG
and apply the following configuration:
import reactor.netty.http.client.HttpClient;
public class Application {
public static void main(String[] args) {
HttpClient client =
HttpClient.create()
.wiretap(true); (1)
client.get()
.uri("https://example.com/")
.response()
.block();
}
}
1 | Enables the wire logging |
Wire Logger formatters
Reactor Netty supports 3 different formatters:
-
AdvancedByteBufFormat#HEX_DUMP - the default
/**
* When wire logging is enabled with this format, both events and content will be logged.
* The content will be in hex format.
* <p>Examples:</p>
* <pre>
* {@code
* reactor.netty.http.HttpTests - [d5230a14, L:/0:0:0:0:0:0:0:1:60267 - R:/0:0:0:0:0:0:0:1:60269] REGISTERED
* reactor.netty.http.HttpTests - [d5230a14, L:/0:0:0:0:0:0:0:1:60267 - R:/0:0:0:0:0:0:0:1:60269] ACTIVE
* reactor.netty.http.HttpTests - [d5230a14, L:/0:0:0:0:0:0:0:1:60267 - R:/0:0:0:0:0:0:0:1:60269] READ: 145B
* +-------------------------------------------------+
* | 0 1 2 3 4 5 6 7 8 9 a b c d e f |
* +--------+-------------------------------------------------+----------------+
* |00000000| 50 4f 53 54 20 2f 74 65 73 74 2f 57 6f 72 6c 64 |POST /test/World|
* |00000010| 20 48 54 54 50 2f 31 2e 31 0d 0a 43 6f 6e 74 65 | HTTP/1.1..Conte|
* |00000020| 6e 74 2d 54 79 70 65 3a 20 74 65 78 74 2f 70 6c |nt-Type: text/pl|
* |00000030| 61 69 6e 0d 0a 75 73 65 72 2d 61 67 65 6e 74 3a |ain..user-agent:|
* |00000040| 20 52 65 61 63 74 6f 72 4e 65 74 74 79 2f 64 65 | ReactorNetty/de|
* ...
* reactor.netty.http.HttpTests - [d5230a14, L:/0:0:0:0:0:0:0:1:60267 - R:/0:0:0:0:0:0:0:1:60269] WRITE: 38B
* +-------------------------------------------------+
* | 0 1 2 3 4 5 6 7 8 9 a b c d e f |
* +--------+-------------------------------------------------+----------------+
* |00000000| 48 54 54 50 2f 31 2e 31 20 32 30 30 20 4f 4b 0d |HTTP/1.1 200 OK.|
* |00000010| 0a 63 6f 6e 74 65 6e 74 2d 6c 65 6e 67 74 68 3a |.content-length:|
* |00000020| 20 30 0d 0a 0d 0a | 0.... |
* +--------+-------------------------------------------------+----------------+
* }
* </pre>
*/
/**
* When wire logging is enabled with this format, only the events will be logged.
* <p>Examples:</p>
* <pre>
* {@code
* reactor.netty.http.HttpTests - [230d3686, L:/0:0:0:0:0:0:0:1:60241 - R:/0:0:0:0:0:0:0:1:60245] REGISTERED
* reactor.netty.http.HttpTests - [230d3686, L:/0:0:0:0:0:0:0:1:60241 - R:/0:0:0:0:0:0:0:1:60245] ACTIVE
* reactor.netty.http.HttpTests - [230d3686, L:/0:0:0:0:0:0:0:1:60241 - R:/0:0:0:0:0:0:0:1:60245] READ: 145B
* reactor.netty.http.HttpTests - [230d3686, L:/0:0:0:0:0:0:0:1:60241 - R:/0:0:0:0:0:0:0:1:60245] WRITE: 38B
* }
* </pre>
*/
/**
* When wire logging is enabled with this format, both events and content will be logged.
* The content will be in plain text format.
* <p>Examples:</p>
* <pre>
* {@code
* reactor.netty.http.HttpTests - [02c3db6c, L:/0:0:0:0:0:0:0:1:60317 - R:/0:0:0:0:0:0:0:1:60319] REGISTERED
* reactor.netty.http.HttpTests - [02c3db6c, L:/0:0:0:0:0:0:0:1:60317 - R:/0:0:0:0:0:0:0:1:60319] ACTIVE
* reactor.netty.http.HttpTests - [02c3db6c, L:/0:0:0:0:0:0:0:1:60317 - R:/0:0:0:0:0:0:0:1:60319] READ: 145B POST /test/World HTTP/1.1
* Content-Type: text/plain
* user-agent: ReactorNetty/dev
* ...
* reactor.netty.http.HttpTests - [02c3db6c, L:/0:0:0:0:0:0:0:1:60317 - R:/0:0:0:0:0:0:0:1:60319] WRITE: 38B HTTP/1.1 200 OK
* content-length: 0
* }
* </pre>
*/
When you need to change the default formatter you can configure it as follows:
import io.netty.handler.logging.LogLevel;
import reactor.netty.http.client.HttpClient;
import reactor.netty.transport.logging.AdvancedByteBufFormat;
public class Application {
public static void main(String[] args) {
HttpClient client =
HttpClient.create()
.wiretap("logger-name", LogLevel.DEBUG, AdvancedByteBufFormat.TEXTUAL); (1)
client.get()
.uri("https://example.com/")
.response()
.block();
}
}
1 | Enables the wire logging, AdvancedByteBufFormat#TEXTUAL is used for printing the content. |
6.7. Connection Pool
By default, HttpClient
uses a “fixed” connection pool with 500
as the maximum number of active channels
and 1000
as the maximum number of further channel acquisition attempts allowed to be kept in a pending state
(for the rest of the configurations check the system properties or the builder configurations below).
This means that the implementation creates a new channel if someone tries to acquire a channel
as long as less than 500
have been created and are managed by the pool.
When the maximum number of channels in the pool is reached, up to 1000
new attempts to
acquire a channel are delayed (pending) until a channel is returned to the pool again,
and further attempts are declined with an error.
/**
* Default max connections. Fallback to
* 2 * available number of processors (but with a minimum value of 16)
*/
public static final String POOL_MAX_CONNECTIONS = "reactor.netty.pool.maxConnections";
/**
* Default acquisition timeout (milliseconds) before error. If -1 will never wait to
* acquire before opening a new
* connection in an unbounded fashion. Fallback 45 seconds
*/
public static final String POOL_ACQUIRE_TIMEOUT = "reactor.netty.pool.acquireTimeout";
/**
* Default max idle time, fallback - max idle time is not specified.
* <p><strong>Note:</strong> This configuration is not applicable for {@link reactor.netty.tcp.TcpClient}.
* A TCP connection is always closed and never returned to the pool.
*/
public static final String POOL_MAX_IDLE_TIME = "reactor.netty.pool.maxIdleTime";
/**
* Default max life time, fallback - max life time is not specified.
* <p><strong>Note:</strong> This configuration is not applicable for {@link reactor.netty.tcp.TcpClient}.
* A TCP connection is always closed and never returned to the pool.
*/
public static final String POOL_MAX_LIFE_TIME = "reactor.netty.pool.maxLifeTime";
/**
* Default leasing strategy (fifo, lifo), fallback to fifo.
* <ul>
* <li>fifo - The connection selection is first in, first out</li>
* <li>lifo - The connection selection is last in, first out</li>
* </ul>
* <p><strong>Note:</strong> This configuration is not applicable for {@link reactor.netty.tcp.TcpClient}.
* A TCP connection is always closed and never returned to the pool.
*/
public static final String POOL_LEASING_STRATEGY = "reactor.netty.pool.leasingStrategy";
/**
* Default {@code getPermitsSamplingRate} (between 0d and 1d (percentage))
* to be used with a {@link SamplingAllocationStrategy}.
* This strategy wraps a {@link PoolBuilder#sizeBetween(int, int) sizeBetween} {@link AllocationStrategy}
* and samples calls to {@link AllocationStrategy#getPermits(int)}.
* Fallback - sampling is not enabled.
*/
public static final String POOL_GET_PERMITS_SAMPLING_RATE = "reactor.netty.pool.getPermitsSamplingRate";
/**
* Default {@code returnPermitsSamplingRate} (between 0d and 1d (percentage))
When you need to change the default settings, you can configure the ConnectionProvider
as follows:
import reactor.netty.http.client.HttpClient;
import reactor.netty.resources.ConnectionProvider;
import java.time.Duration;
public class Application {
public static void main(String[] args) {
ConnectionProvider provider =
ConnectionProvider.builder("custom")
.maxConnections(50)
.maxIdleTime(Duration.ofSeconds(20)) (1)
.maxLifeTime(Duration.ofSeconds(60)) (2)
.pendingAcquireTimeout(Duration.ofSeconds(60)) (3)
.evictInBackground(Duration.ofSeconds(120)) (4)
.build();
HttpClient client = HttpClient.create(provider);
String response =
client.get()
.uri("https://example.com/")
.responseContent()
.aggregate()
.asString()
.block();
System.out.println("Response " + response);
provider.disposeLater()
.block();
}
}
1 | Configures the maximum time for a connection to stay idle to 20 seconds. |
2 | Configures the maximum time for a connection to stay alive to 60 seconds. |
3 | Configures the maximum time for the pending acquire operation to 60 seconds. |
4 | Every two minutes, the connection pool is regularly checked for connections that are applicable for removal. |
Notice that only the default HttpClient (HttpClient.create() ) uses 500 as the maximum number of active channels. In the example above, when
instantiating a custom ConnectionProvider , we are changing this value to 50 using maxConnections . Also, if you don’t set this parameter the
default maxConnections is used (2 * available number of processors).
|
The following listing shows the available configurations:
Configuration name | Description |
---|---|
|
When this option is enabled, connection pools are regularly checked in the background, and those that are empty and been inactive for a specified time become eligible for disposal. By default, this background disposal of inactive pools is disabled. |
|
When |
|
When this option is enabled, each connection pool regularly checks for connections that are
eligible for removal according to eviction criteria like |
|
Configure the connection pool so that if there are idle connections (i.e. pool is under-utilized),
the next acquire operation will get the |
|
Configure the connection pool so that if there are idle connections (i.e. pool is under-utilized),
the next acquire operation will get the |
|
The maximum number of connections (per connection pool) before start pending. Default to 2 * available number of processors (but with a minimum value of 16). |
|
The time after which the channel is eligible to be closed when idle (resolution: ms). Default: max idle time is not specified. |
|
The total life time after which the channel is eligible to be closed (resolution: ms). Default: max life time is not specified. |
|
Enables/disables built-in integration with Micrometer. |
|
The maximum number of extra attempts at acquiring a connection to keep in a pending queue. If -1 is specified, the pending queue does not have upper limit. Default to 2 * max connections. |
|
The maximum time before which a pending acquire must complete, or a TimeoutException is thrown (resolution: ms). If -1 is specified, no such timeout is applied. Default: 45 seconds. |
When you expect a high load, be cautious with a connection pool with a very high value for maximum connections. You might experience
reactor.netty.http.client.PrematureCloseException exception with a root cause "Connect Timeout" due
to too many concurrent connections opened/acquired.
|
If you need to disable the connection pool, you can apply the following configuration:
import reactor.netty.http.client.HttpClient;
public class Application {
public static void main(String[] args) {
HttpClient client =
HttpClient.newConnection()
.doOnConnected(conn -> System.out.println("Connection " + conn.channel()));
String response =
// A new connection is established for every request
client.get()
.uri("https://httpbin.org/get")
.responseContent()
.aggregate()
.asString()
.block();
System.out.println("Response " + response);
response =
// A new connection is established for every request
client.post()
.uri("https://httpbin.org/post")
.responseContent()
.aggregate()
.asString()
.block();
System.out.println("Response " + response);
}
}
6.7.1. Metrics
The pooled ConnectionProvider
supports built-in integration with Micrometer
.
It exposes all metrics with a prefix of reactor.netty.connection.provider
.
Pooled ConnectionProvider
metrics
metric name | type | description |
---|---|---|
reactor.netty.connection.provider.total.connections |
Gauge |
The number of all connections, active or idle |
reactor.netty.connection.provider.active.connections |
Gauge |
The number of the connections that have been successfully acquired and are in active use |
reactor.netty.connection.provider.max.connections |
Gauge |
The maximum number of active connections that are allowed |
reactor.netty.connection.provider.idle.connections |
Gauge |
The number of the idle connections |
reactor.netty.connection.provider.pending.connections |
Gauge |
The number of requests that are waiting for a connection |
reactor.netty.connection.provider.max.pending.connections |
Gauge |
The maximum number of requests that will be queued while waiting for a ready connection |
The following example enables that integration:
import reactor.netty.http.client.HttpClient;
import reactor.netty.resources.ConnectionProvider;
public class Application {
public static void main(String[] args) {
ConnectionProvider provider =
ConnectionProvider.builder("custom")
.maxConnections(50)
.metrics(true) (1)
.build();
HttpClient client = HttpClient.create(provider);
String response =
client.get()
.uri("https://example.com/")
.responseContent()
.aggregate()
.asString()
.block();
System.out.println("Response " + response);
provider.disposeLater()
.block();
}
}
1 | Enables the built-in integration with Micrometer |
6.8. SSL and TLS
When you need SSL or TLS, you can apply the configuration shown in the next example.
By default, if OpenSSL
is available, a
SslProvider.OPENSSL
provider is used as a provider. Otherwise, a
SslProvider.JDK provider is used
You can switch the provider by using
SslContextBuilder
or by setting -Dio.netty.handler.ssl.noOpenSsl=true
.
The following example uses SslContextBuilder
:
import reactor.netty.http.Http11SslContextSpec;
import reactor.netty.http.client.HttpClient;
public class Application {
public static void main(String[] args) {
Http11SslContextSpec http11SslContextSpec = Http11SslContextSpec.forClient();
HttpClient client =
HttpClient.create()
.secure(spec -> spec.sslContext(http11SslContextSpec));
client.get()
.uri("https://example.com/")
.response()
.block();
}
}
6.8.1. Server Name Indication
By default, the HTTP
client sends the remote host name as SNI
server name.
When you need to change this default setting, you can configure the HTTP
client as follows:
import io.netty.handler.ssl.SslContext;
import io.netty.handler.ssl.SslContextBuilder;
import reactor.netty.http.client.HttpClient;
import javax.net.ssl.SNIHostName;
public class Application {
public static void main(String[] args) throws Exception {
SslContext sslContext = SslContextBuilder.forClient().build();
HttpClient client =
HttpClient.create()
.secure(spec -> spec.sslContext(sslContext)
.serverNames(new SNIHostName("test.com")));
client.get()
.uri("https://127.0.0.1:8080/")
.response()
.block();
}
}
6.9. Retry Strategies
By default, the HTTP
client retries the request once if it was aborted on the TCP
level.
6.10. HTTP/2
By default, the HTTP
client supports HTTP/1.1
. If you need HTTP/2
, you can get it through configuration.
In addition to the protocol configuration, if you need H2
but not H2C (cleartext)
, you must also configure SSL.
As Application-Layer Protocol Negotiation (ALPN) is not supported “out-of-the-box” by JDK8 (although some vendors backported ALPN to JDK8), you need an additional dependency to a native library that
supports it — for example, netty-tcnative-boringssl-static .
|
The following listing presents a simple H2
example:
import io.netty.handler.codec.http.HttpHeaders;
import reactor.core.publisher.Mono;
import reactor.netty.http.HttpProtocol;
import reactor.netty.http.client.HttpClient;
import reactor.util.function.Tuple2;
public class H2Application {
public static void main(String[] args) {
HttpClient client =
HttpClient.create()
.protocol(HttpProtocol.H2) (1)
.secure(); (2)
Tuple2<String, HttpHeaders> response =
client.get()
.uri("https://example.com/")
.responseSingle((res, bytes) -> bytes.asString()
.zipWith(Mono.just(res.responseHeaders())))
.block();
System.out.println("Used stream ID: " + response.getT2().get("x-http2-stream-id"));
System.out.println("Response: " + response.getT1());
}
}
1 | Configures the client to support only HTTP/2 |
2 | Configures SSL |
The following listing presents a simple H2C
example:
import io.netty.handler.codec.http.HttpHeaders;
import reactor.core.publisher.Mono;
import reactor.netty.http.HttpProtocol;
import reactor.netty.http.client.HttpClient;
import reactor.util.function.Tuple2;
public class H2CApplication {
public static void main(String[] args) {
HttpClient client =
HttpClient.create()
.protocol(HttpProtocol.H2C);
Tuple2<String, HttpHeaders> response =
client.get()
.uri("http://localhost:8080/")
.responseSingle((res, bytes) -> bytes.asString()
.zipWith(Mono.just(res.responseHeaders())))
.block();
System.out.println("Used stream ID: " + response.getT2().get("x-http2-stream-id"));
System.out.println("Response: " + response.getT1());
}
}
6.10.1. Protocol Selection
public enum HttpProtocol {
/**
* The default supported HTTP protocol by HttpServer and HttpClient
*/
HTTP11,
/**
* HTTP/2.0 support with TLS
* <p>If used along with HTTP/1.1 protocol, HTTP/2.0 will be the preferred protocol.
* While negotiating the application level protocol, HTTP/2.0 or HTTP/1.1 can be chosen.
* <p>If used without HTTP/1.1 protocol, HTTP/2.0 will always be offered as a protocol
* for communication with no fallback to HTTP/1.1.
*/
H2,
/**
* HTTP/2.0 support with clear-text.
* <p>If used along with HTTP/1.1 protocol, will support H2C "upgrade":
* Request or consume requests as HTTP/1.1 first, looking for HTTP/2.0 headers
* and {@literal Connection: Upgrade}. A server will typically reply a successful
* 101 status if upgrade is successful or a fallback HTTP/1.1 response. When
* successful the client will start sending HTTP/2.0 traffic.
* <p>If used without HTTP/1.1 protocol, will support H2C "prior-knowledge": Doesn't
* require {@literal Connection: Upgrade} handshake between a client and server but
* fallback to HTTP/1.1 will not be supported.
*/
H2C
}
6.11. Proxy Support
Reactor Netty supports the proxy functionality provided by Netty and provides a way
to specify non proxy hosts
through the ProxyProvider
builder.
Netty’s HTTP proxy support always uses CONNECT
method in order to establish a tunnel to the specified proxy regardless of the scheme that is used http
or https
.
(More information: Netty enforce HTTP proxy to support HTTP CONNECT method).
Some proxies might not support CONNECT
method when the scheme is http
or might need to be configured in order to support this way of communication.
Sometimes this might be the reason for not being able to connect to the proxy. Consider checking the proxy documentation
whether it supports or needs an additional configuration in order to support CONNECT
method.
The following example uses ProxyProvider
:
import reactor.netty.http.client.HttpClient;
import reactor.netty.transport.ProxyProvider;
public class Application {
public static void main(String[] args) {
HttpClient client =
HttpClient.create()
.proxy(spec -> spec.type(ProxyProvider.Proxy.HTTP)
.host("proxy")
.port(8080)
.nonProxyHosts("localhost")
.connectTimeoutMillis(20_000)); (1)
String response =
client.get()
.uri("https://example.com/")
.responseContent()
.aggregate()
.asString()
.block();
1 | Configures the connection establishment timeout to 20 seconds. |
6.12. Metrics
The HTTP client supports built-in integration with Micrometer
.
It exposes all metrics with a prefix of reactor.netty.http.client
.
The following table provides information for the HTTP client metrics:
metric name | type | description |
---|---|---|
reactor.netty.http.client.data.received |
DistributionSummary |
Amount of the data received, in bytes |
reactor.netty.http.client.data.sent |
DistributionSummary |
Amount of the data sent, in bytes |
reactor.netty.http.client.errors |
Counter |
Number of errors that occurred |
reactor.netty.http.client.tls.handshake.time |
Timer |
Time spent for TLS handshake |
reactor.netty.http.client.connect.time |
Timer |
Time spent for connecting to the remote address |
reactor.netty.http.client.address.resolver |
Timer |
Time spent for resolving the address |
reactor.netty.http.client.data.received.time |
Timer |
Time spent in consuming incoming data |
reactor.netty.http.client.data.sent.time |
Timer |
Time spent in sending outgoing data |
reactor.netty.http.client.response.time |
Timer |
Total time for the request/response |
These additional metrics are also available:
Pooled ConnectionProvider
metrics
metric name | type | description |
---|---|---|
reactor.netty.connection.provider.total.connections |
Gauge |
The number of all connections, active or idle |
reactor.netty.connection.provider.active.connections |
Gauge |
The number of the connections that have been successfully acquired and are in active use |
reactor.netty.connection.provider.max.connections |
Gauge |
The maximum number of active connections that are allowed |
reactor.netty.connection.provider.idle.connections |
Gauge |
The number of the idle connections |
reactor.netty.connection.provider.pending.connections |
Gauge |
The number of requests that are waiting for a connection |
reactor.netty.connection.provider.max.pending.connections |
Gauge |
The maximum number of requests that will be queued while waiting for a ready connection |
The following table provides information for the HTTP client metrics when it is configured to serve HTTP/2
traffic:
metric name | type | description |
---|---|---|
reactor.netty.connection.provider.active.streams |
Gauge |
The number of the active HTTP/2 streams |
reactor.netty.connection.provider.pending.streams |
Gauge |
The number of requests that are waiting for opening HTTP/2 stream |
ByteBufAllocator
metrics
metric name | type | description |
---|---|---|
reactor.netty.bytebuf.allocator.used.heap.memory |
Gauge |
The number of bytes reserved by heap buffer allocator |
reactor.netty.bytebuf.allocator.used.direct.memory |
Gauge |
The number of bytes reserved by direct buffer allocator |
reactor.netty.bytebuf.allocator.used.heap.arenas |
Gauge |
The number of heap arenas (when |
reactor.netty.bytebuf.allocator.used.direct.arenas |
Gauge |
The number of direct arenas (when |
reactor.netty.bytebuf.allocator.used.threadlocal.caches |
Gauge |
The number of thread local caches (when |
reactor.netty.bytebuf.allocator.used.small.cache.size |
Gauge |
The size of the small cache (when |
reactor.netty.bytebuf.allocator.used.normal.cache.size |
Gauge |
The size of the normal cache (when |
reactor.netty.bytebuf.allocator.used.chunk.size |
Gauge |
The chunk size for an arena (when |
reactor.netty.bytebuf.allocator.active.heap.buffers |
Gauge |
The actual bytes consumed by in-use heap buffers (when |
reactor.netty.bytebuf.allocator.active.direct.buffers |
Gauge |
The actual bytes consumed by in-use direct buffers (when |
EventLoop
metrics
metric name | type | description |
---|---|---|
reactor.netty.eventloop.pending.tasks |
Gauge |
The number of tasks that are pending for processing on an event loop |
The following example enables that integration:
import io.micrometer.core.instrument.Metrics;
import io.micrometer.core.instrument.config.MeterFilter;
import reactor.netty.http.client.HttpClient;
public class Application {
public static void main(String[] args) {
Metrics.globalRegistry (1)
.config()
.meterFilter(MeterFilter.maximumAllowableTags("reactor.netty.http.client", "URI", 100, MeterFilter.deny()));
HttpClient client =
HttpClient.create()
.metrics(true, s -> {
if (s.startsWith("/stream/")) { (2)
return "/stream/{n}";
}
else if (s.startsWith("/bytes/")) {
return "/bytes/{n}";
}
return s;
}); (3)
client.get()
.uri("https://httpbin.org/stream/2")
.responseContent()
.blockLast();
client.get()
.uri("https://httpbin.org/bytes/1024")
.responseContent()
.blockLast();
}
}
1 | Applies upper limit for the meters with URI tag |
2 | Templated URIs will be used as a URI tag value when possible |
3 | Enables the built-in integration with Micrometer |
In order to avoid a memory and CPU overhead of the enabled metrics, it is important to convert the real URIs to templated URIs when possible. Without a conversion to a template-like form, each distinct URI leads to the creation of a distinct tag, which takes a lot of memory for the metrics. |
Always apply an upper limit for the meters with URI tags. Configuring an upper limit on the number of meters can help in cases when the real URIs cannot be templated.
You can find more information at maximumAllowableTags .
|
When HTTP client metrics are needed for an integration with a system other than Micrometer
or you want
to provide your own integration with Micrometer
, you can provide your own metrics recorder, as follows:
import reactor.netty.http.client.HttpClient;
import reactor.netty.http.client.HttpClientMetricsRecorder;
import java.net.SocketAddress;
import java.time.Duration;
public class Application {
public static void main(String[] args) {
HttpClient client =
HttpClient.create()
.metrics(true, CustomHttpClientMetricsRecorder::new); (1)
client.get()
.uri("https://httpbin.org/stream/2")
.response()
.block();
}
1 | Enables HTTP client metrics and provides HttpClientMetricsRecorder implementation. |
6.13. Unix Domain Sockets
The HTTP
client supports Unix Domain Sockets (UDS) when native transport is in use.
The following example shows how to use UDS support:
import io.netty.channel.unix.DomainSocketAddress;
import reactor.netty.http.client.HttpClient;
public class Application {
public static void main(String[] args) {
HttpClient client =
HttpClient.create()
.remoteAddress(() -> new DomainSocketAddress("/tmp/test.sock")); (1)
client.get()
.uri("/")
.response()
.block();
}
}
1 | Specifies DomainSocketAddress that will be used |
6.14. Host Name Resolution
By default, the HttpClient
uses Netty’s domain name lookup mechanism that resolves a domain name asynchronously.
This is as an alternative of the JVM’s built-in blocking resolver.
When you need to change the default settings, you can configure the HttpClient
as follows:
import reactor.netty.http.client.HttpClient;
import java.time.Duration;
public class Application {
public static void main(String[] args) {
HttpClient client =
HttpClient.create()
.resolver(spec -> spec.queryTimeout(Duration.ofMillis(500))); (1)
String response =
client.get()
.uri("https://example.com/")
.responseContent()
.aggregate()
.asString()
.block();
System.out.println("Response " + response);
}
}
1 | The timeout of each DNS query performed by this resolver will be 500ms. |
The following listing shows the available configurations:
Configuration name | Description |
---|---|
|
The max time to live of the cached DNS resource records (resolution: seconds).
If the time to live of the DNS resource record returned by the DNS server is greater
than this max time to live, this resolver ignores the time to live from
the DNS server and uses this max time to live.
Default to |
|
The min time to live of the cached DNS resource records (resolution: seconds). If the time to live of the DNS resource record returned by the DNS server is less than this min time to live, this resolver ignores the time to live from the DNS server and uses this min time to live. Default: 0. |
|
The time to live of the cache for the failed DNS queries (resolution: seconds). Default: 0. |
|
When this setting is enabled, the resolver notifies as soon as all queries for the preferred address type are complete.
When this setting is disabled, the resolver notifies when all possible address types are complete.
This configuration is applicable for |
|
Disables the automatic inclusion of an optional record that tries to give a hint to the remote DNS server about how much data the resolver can read per response. By default, this setting is enabled. |
|
Specifies whether this resolver has to send a DNS query with the recursion desired (RD) flag set. By default, this setting is enabled. |
|
Sets a custom |
|
Sets the capacity of the datagram packet buffer (in bytes). Default: 4096. |
|
Sets the maximum allowed number of DNS queries to send when resolving a host name. Default: 16. |
|
Sets the number of dots that must appear in a name before an initial absolute query is made. Default: -1 (to determine the value from the OS on Unix or use a value of 1 otherwise). |
|
Sets the timeout of each DNS query performed by this resolver (resolution: milliseconds). Default: 5000. |
|
The list of the protocol families of the resolved address. |
|
The supplier of the local address to bind to. |
|
Enables an
|
|
Performs the communication with the DNS servers on the given
|
|
The list of search domains of the resolver. By default, the effective search domain list is populated by using the system DNS search domains. |
|
A specific logger and log level to be used by this resolver when generating detailed trace information in case of resolution failure. |
Sometimes, you may want to switch to the JVM built-in resolver. To do so, you can configure the HttpClient
as follows:
import io.netty.resolver.DefaultAddressResolverGroup;
import reactor.netty.http.client.HttpClient;
public class Application {
public static void main(String[] args) {
HttpClient client =
HttpClient.create()
.resolver(DefaultAddressResolverGroup.INSTANCE); (1)
String response =
client.get()
.uri("https://example.com/")
.responseContent()
.aggregate()
.asString()
.block();
System.out.println("Response " + response);
}
}
1 | Sets the JVM built-in resolver. |
6.15. Timeout Configuration
This section describes various timeout configuration options that can be used in HttpClient
.
Configuring a proper timeout may improve or solve issues in the communication process.
The configuration options can be grouped as follows:
6.15.1. Connection Pool Timeout
By default, HttpClient
uses a connection pool. When a request is completed successfully and if the connection is not scheduled for closing,
the connection is returned to the connection pool and can thus be reused for processing another request. The connection may
be reused immediately for another request or may stay idle in the connection pool for some time.
The following list describes the available timeout configuration options:
-
maxIdleTime
- The maximum time (resolution: ms) that this connection stays idle in the connection pool. By default,maxIdleTime
is not specified.
When you configure maxIdleTime , you should consider the idle timeout configuration on the target server.
Choose a configuration that is equal to or less than the one on the target server. By doing so, you can reduce the I/O
issues caused by a connection closed by the target server.
|
-
maxLifeTime
- The maximum time (resolution: ms) that this connection stays alive. By default,maxLifeTime
is not specified. -
pendingAcquireTimeout
- The maximum time (resolution: ms) after which a pending acquire operation must complete, or aPoolAcquireTimeoutException
is thrown. Default: 45s.
By default, these timeouts are checked on connection release
or acquire
operations and, if some timeout is reached, the connection is closed and removed from the connection pool.
However, you can also configure the connection pool, by setting evictInBackground
, to perform periodic checks on connections.
To customize the default settings, you can configure HttpClient
as follows:
import reactor.netty.http.client.HttpClient;
import reactor.netty.resources.ConnectionProvider;
import java.time.Duration;
public class Application {
public static void main(String[] args) {
ConnectionProvider provider =
ConnectionProvider.builder("custom")
.maxConnections(50)
.maxIdleTime(Duration.ofSeconds(20)) (1)
.maxLifeTime(Duration.ofSeconds(60)) (2)
.pendingAcquireTimeout(Duration.ofSeconds(60)) (3)
.evictInBackground(Duration.ofSeconds(120)) (4)
.build();
HttpClient client = HttpClient.create(provider);
String response =
client.get()
.uri("https://example.com/")
.responseContent()
.aggregate()
.asString()
.block();
System.out.println("Response " + response);
provider.disposeLater()
.block();
}
}
1 | Configures the maximum time for a connection to stay idle to 20 seconds. |
2 | Configures the maximum time for a connection to stay alive to 60 seconds. |
3 | Configures the maximum time for the pending acquire operation to 60 seconds. |
4 | Every two minutes, the connection pool is regularly checked for connections that are applicable for removal. |
6.15.2. HttpClient Timeout
This section provides information for the various timeout configuration options at the HttpClient
level.
Reactor Netty uses Reactor Core as its Reactive Streams implementation, and you may want to use the timeout operator that Mono and Flux provide.
Keep in mind, however, that it is better to use the more specific timeout configuration options available in Reactor Netty, since they provide more control for a specific purpose and use case.
By contrast, the timeout operator can only apply to the operation as a whole, from establishing the connection to the remote peer to receiving the response.
|
Response Timeout
HttpClient
provides an API for configuring a default response timeout for all requests. You can change this default response timeout
through an API for a specific request. By default,
responseTimeout
is not specified.
It is always a good practice to configure a response timeout. |
To customize the default settings, you can configure HttpClient
as follows:
import reactor.core.publisher.Mono;
import reactor.netty.http.client.HttpClient;
import java.time.Duration;
public class Application {
public static void main(String[] args) {
HttpClient client =
HttpClient.create()
.responseTimeout(Duration.ofSeconds(1)); (1)
String response1 =
client.post()
.uri("https://example.com/")
.send((req, out) -> {
req.responseTimeout(Duration.ofSeconds(2)); (2)
return out.sendString(Mono.just("body1"));
})
.responseContent()
.aggregate()
.asString()
.block();
System.out.println("Response " + response1);
String response2 =
client.post()
.uri("https://example.com/")
.send((req, out) -> out.sendString(Mono.just("body2")))
.responseContent()
.aggregate()
.asString()
.block();
System.out.println("Response " + response2);
}
}
1 | Configures the default response timeout to 1 second. |
2 | Configures a response timeout for a specific request to 2 seconds. |
Connection Timeout
The following listing shows all available connection timeout configuration options, but some of them may apply only to a specific transport.
-
CONNECT_TIMEOUT_MILLIS
- If the connection establishment attempt to the remote peer does not finish within the configured connect timeout (resolution: ms), the connection establishment attempt fails. Default: 30s. -
SO_KEEPALIVE
- When the connection stays idle for some time (the time is implementation dependent, but the default is typically two hours), TCP automatically sends akeepalive
probe to the remote peer. By default,SO_KEEPALIVE
is not enabled. When you run withEpoll
/NIO
(since Java 11 on Mac or Linux) transport, you may also configure:-
TCP_KEEPIDLE
- The maximum time (resolution: seconds) that this connection stays idle before TCP starts sendingkeepalive
probes, ifSO_KEEPALIVE
has been set. The maximum time is implementation dependent, but the default is typically two hours. -
TCP_KEEPINTVL
(Epoll)/TCP_KEEPINTERVAL
(NIO) - The time (resolution: seconds) between individualkeepalive
probes. -
TCP_KEEPCNT
(Epoll)/TCP_KEEPCOUNT
(NIO) - The maximum number ofkeepalive
probes TCP should send before dropping the connection.
-
Sometimes, between the client and the server, you may have a network component that silently drops the idle connections without sending a response.
From the Reactor Netty point of view, in this use case, the remote peer just does not respond.
To be able to handle such a use case you may consider configuring
SO_KEEPALIVE .
|
To customize the default settings, you can configure HttpClient
as follows:
import io.netty.channel.ChannelOption;
import io.netty.channel.epoll.EpollChannelOption;
//import io.netty.channel.socket.nio.NioChannelOption;
//import jdk.net.ExtendedSocketOptions;
import reactor.netty.http.client.HttpClient;
import java.net.InetSocketAddress;
public class Application {
public static void main(String[] args) {
HttpClient client =
HttpClient.create()
.bindAddress(() -> new InetSocketAddress("host", 1234))
.option(ChannelOption.CONNECT_TIMEOUT_MILLIS, 10000) (1)
.option(ChannelOption.SO_KEEPALIVE, true) (2)
// The options below are available only when NIO transport (Java 11) is used
// on Mac or Linux (Java does not currently support these extended options on Windows)
// https://bugs.openjdk.java.net/browse/JDK-8194298
//.option(NioChannelOption.of(ExtendedSocketOptions.TCP_KEEPIDLE), 300)
//.option(NioChannelOption.of(ExtendedSocketOptions.TCP_KEEPINTERVAL), 60)
//.option(NioChannelOption.of(ExtendedSocketOptions.TCP_KEEPCOUNT), 8);
// The options below are available only when Epoll transport is used
.option(EpollChannelOption.TCP_KEEPIDLE, 300) (3)
.option(EpollChannelOption.TCP_KEEPINTVL, 60) (4)
.option(EpollChannelOption.TCP_KEEPCNT, 8); (5)
String response =
client.get()
.uri("https://example.com/")
.responseContent()
.aggregate()
.asString()
.block();
System.out.println("Response " + response);
1 | Configures the connection establishment timeout to 10 seconds. |
2 | Enables TCP keepalive . This means that TCP starts sending keepalive probes when a connection is idle for some time. |
3 | The connection needs to remain idle for 5 minutes before TCP starts sending keepalive probes. |
4 | Configures the time between individual keepalive probes to 1 minute. |
5 | Configures the maximum number of TCP keepalive probes to 8. |
SSL/TLS Timeout
HttpClient
supports the SSL/TLS functionality provided by Netty.
The following list describes the available timeout configuration options:
-
handshakeTimeout
- Use this option to configure the SSL handshake timeout (resolution: ms). Default: 10s.
You should consider increasing the SSL handshake timeout when expecting slow network connections. |
-
closeNotifyFlushTimeout
- Use this option to configure the SSLclose_notify
flush timeout (resolution: ms). Default: 3s. -
closeNotifyReadTimeout
- Use this option to configure the SSLclose_notify
read timeout (resolution: ms). Default: 0s.
To customize the default settings, you can configure HttpClient
as follows:
import reactor.netty.http.Http11SslContextSpec;
import reactor.netty.http.client.HttpClient;
import java.time.Duration;
public class Application {
public static void main(String[] args) {
Http11SslContextSpec http11SslContextSpec = Http11SslContextSpec.forClient();
HttpClient client =
HttpClient.create()
.secure(spec -> spec.sslContext(http11SslContextSpec)
.handshakeTimeout(Duration.ofSeconds(30)) (1)
.closeNotifyFlushTimeout(Duration.ofSeconds(10)) (2)
.closeNotifyReadTimeout(Duration.ofSeconds(10))); (3)
String response =
client.get()
.uri("https://example.com/")
.responseContent()
.aggregate()
.asString()
.block();
System.out.println("Response " + response);
}
}
1 | Configures the SSL handshake timeout to 30 seconds. |
2 | Configures the SSL close_notify flush timeout to 10 seconds. |
3 | Configures the SSL close_notify read timeout to 10 seconds. |
Proxy Timeout
HttpClient
supports the proxy functionality provided by Netty and provides a way to specify the
connection establishment timeout.
If the connection establishment attempt to the remote peer does not finish within the timeout,
the connection establishment attempt fails. Default: 10s.
To customize the default settings, you can configure HttpClient
as follows:
import reactor.netty.http.client.HttpClient;
import reactor.netty.transport.ProxyProvider;
public class Application {
public static void main(String[] args) {
HttpClient client =
HttpClient.create()
.proxy(spec -> spec.type(ProxyProvider.Proxy.HTTP)
.host("proxy")
.port(8080)
.nonProxyHosts("localhost")
.connectTimeoutMillis(20_000)); (1)
String response =
client.get()
.uri("https://example.com/")
.responseContent()
.aggregate()
.asString()
.block();
System.out.println("Response " + response);
}
1 | Configures the connection establishment timeout to 20 seconds. |
Host Name Resolution Timeout
By default, the HttpClient
uses Netty’s domain name lookup mechanism to resolve a domain name asynchronously.
The following list describes the available timeout configuration options:
-
cacheMaxTimeToLive
- The maximum time to live of the cached DNS resource records (resolution: seconds). If the time to live of the DNS resource record returned by the DNS server is greater than this maximum time to live, this resolver ignores the time to live from the DNS server and uses this maximum time to live. Default:Integer.MAX_VALUE
. -
cacheMinTimeToLive
- The minimum time to live of the cached DNS resource records (resolution: seconds). If the time to live of the DNS resource record returned by the DNS server is less than this minimum time to live, this resolver ignores the time to live from the DNS server and uses this minimum time to live. Default: 0s. -
cacheNegativeTimeToLive
- The time to live of the cache for the failed DNS queries (resolution: seconds). Default: 0s. -
queryTimeout
- Sets the timeout of each DNS query performed by this resolver (resolution: milliseconds). Default: 5s.
To customize the default settings, you can configure HttpClient
as follows:
import reactor.netty.http.client.HttpClient;
import java.time.Duration;
public class Application {
public static void main(String[] args) {
HttpClient client =
HttpClient.create()
.resolver(spec -> spec.queryTimeout(Duration.ofMillis(500))); (1)
String response =
client.get()
.uri("https://example.com/")
.responseContent()
.aggregate()
.asString()
.block();
System.out.println("Response " + response);
}
}
1 | The timeout of each DNS query performed by this resolver will be 500ms. |
Suggest Edit to "HTTP Client"
7. UDP Server
Reactor Netty provides the easy-to-use and easy-to-configure
UdpServer
.
It hides most of the Netty functionality that is required to create a UDP
server
and adds Reactive Streams
backpressure.
7.1. Starting and Stopping
To start a UDP server, a UdpServer
instance has to be created and configured.
By default, the host is configured to be localhost
and the port is 12012
.
The following example shows how to create and start a UDP server:
import reactor.netty.Connection;
import reactor.netty.udp.UdpServer;
import java.time.Duration;
public class Application {
public static void main(String[] args) {
Connection server =
UdpServer.create() (1)
.bindNow(Duration.ofSeconds(30)); (2)
server.onDispose()
.block();
}
}
1 | Creates a UdpServer
instance that is ready for configuring. |
2 | Starts the server in a blocking fashion and waits for it to finish initializing. |
The returned Connection
offers a simple server API, including disposeNow()
,
which shuts the server down in a blocking fashion.
7.1.1. Host and Port
In order to serve on a specific host and port, you can apply the following configuration to the UDP
server:
import reactor.netty.Connection;
import reactor.netty.udp.UdpServer;
import java.time.Duration;
public class Application {
public static void main(String[] args) {
Connection server =
UdpServer.create()
.host("localhost") (1)
.port(8080) (2)
.bindNow(Duration.ofSeconds(30));
server.onDispose()
.block();
}
}
1 | Configures the UDP server host |
2 | Configures the UDP server port |
7.2. Eager Initialization
By default, the initialization of the UdpServer
resources happens on demand. This means that the bind
operation
absorbs the extra time needed to initialize and load:
-
the event loop group
-
the native transport libraries (when native transport is used)
When you need to preload these resources, you can configure the UdpServer
as follows:
import io.netty.channel.socket.DatagramPacket;
import reactor.core.publisher.Mono;
import reactor.netty.Connection;
import reactor.netty.udp.UdpServer;
import java.time.Duration;
public class Application {
public static void main(String[] args) {
UdpServer udpServer =
UdpServer.create()
.handle((in, out) ->
out.sendObject(
in.receiveObject()
.map(o -> {
if (o instanceof DatagramPacket) {
DatagramPacket p = (DatagramPacket) o;
return new DatagramPacket(p.content().retain(), p.sender());
}
else {
return Mono.error(new Exception("Unexpected type of the message: " + o));
}
})));
udpServer.warmup() (1)
.block();
Connection server = udpServer.bindNow(Duration.ofSeconds(30));
server.onDispose()
.block();
}
}
1 | Initialize and load the event loop group and the native transport libraries |
7.3. Writing Data
To send data to the remote peer, you must attach an I/O handler.
The I/O handler has access to UdpOutbound
,
to be able to write data.
The following example shows how to send hello
:
import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.socket.DatagramPacket;
import io.netty.util.CharsetUtil;
import reactor.core.publisher.Mono;
import reactor.netty.Connection;
import reactor.netty.udp.UdpServer;
import java.time.Duration;
public class Application {
public static void main(String[] args) {
Connection server =
UdpServer.create()
.handle((in, out) ->
out.sendObject(
in.receiveObject()
.map(o -> {
if (o instanceof DatagramPacket) {
DatagramPacket p = (DatagramPacket) o;
ByteBuf buf = Unpooled.copiedBuffer("hello", CharsetUtil.UTF_8);
return new DatagramPacket(buf, p.sender()); (1)
}
else {
return Mono.error(new Exception("Unexpected type of the message: " + o));
}
})))
.bindNow(Duration.ofSeconds(30));
server.onDispose()
.block();
}
}
1 | Sends a hello string to the remote peer |
7.4. Consuming Data
To receive data from a remote peer, you must attach an I/O handler.
The I/O handler has access to UdpInbound
,
to be able to read data.
The following example shows how to consume data:
import io.netty.channel.socket.DatagramPacket;
import reactor.core.publisher.Mono;
import reactor.netty.Connection;
import reactor.netty.udp.UdpServer;
import java.time.Duration;
public class Application {
public static void main(String[] args) {
Connection server =
UdpServer.create()
.handle((in, out) ->
out.sendObject(
in.receiveObject()
.map(o -> {
if (o instanceof DatagramPacket) {
DatagramPacket p = (DatagramPacket) o;
return new DatagramPacket(p.content().retain(), p.sender()); (1)
}
else {
return Mono.error(new Exception("Unexpected type of the message: " + o));
}
})))
.bindNow(Duration.ofSeconds(30));
server.onDispose()
.block();
}
}
1 | Receives data from the remote peer |
7.5. Lifecycle Callbacks
The following lifecycle callbacks are provided to let you extend the UdpServer
:
Callback | Description |
---|---|
|
Invoked when the server channel is about to bind. |
|
Invoked when the server channel is bound. |
|
Invoked when initializing the channel. |
|
Invoked when the server channel is unbound. |
The following example uses the doOnBound
and doOnChannelInit
callbacks:
import io.netty.handler.codec.LineBasedFrameDecoder;
import io.netty.handler.logging.LoggingHandler;
import reactor.netty.Connection;
import reactor.netty.udp.UdpServer;
import java.time.Duration;
public class Application {
public static void main(String[] args) {
Connection server =
UdpServer.create()
.doOnBound(conn -> conn.addHandlerLast(new LineBasedFrameDecoder(8192))) (1)
.doOnChannelInit((observer, channel, remoteAddress) ->
channel.pipeline()
.addFirst(new LoggingHandler("reactor.netty.examples"))) (2)
.bindNow(Duration.ofSeconds(30));
server.onDispose()
.block();
}
}
1 | Netty pipeline is extended with LineBasedFrameDecoder when the server channel is bound. |
2 | Netty pipeline is extended with LoggingHandler when initializing the channel. |
7.6. Connection Configuration
This section describes three kinds of configuration that you can use at the UDP level:
7.6.1. Channel Options
By default, the UDP
server is configured with the following options:
UdpServerBind() {
this.config = new UdpServerConfig(
Collections.singletonMap(ChannelOption.AUTO_READ, false),
() -> new InetSocketAddress(NetUtil.LOCALHOST, DEFAULT_PORT));
}
If you need additional options or need to change the current options, you can apply the following configuration:
import io.netty.channel.ChannelOption;
import reactor.netty.Connection;
import reactor.netty.udp.UdpServer;
import java.time.Duration;
public class Application {
public static void main(String[] args) {
Connection server =
UdpServer.create()
.option(ChannelOption.CONNECT_TIMEOUT_MILLIS, 10000)
.bindNow(Duration.ofSeconds(30));
server.onDispose()
.block();
}
}
For more information about Netty channel options, see the following links:
7.6.2. Wire Logger
Reactor Netty provides wire logging for when the traffic between the peers needs to be inspected.
By default, wire logging is disabled.
To enable it, you must set the logger reactor.netty.udp.UdpServer
level to DEBUG
and apply the following configuration:
import reactor.netty.Connection;
import reactor.netty.udp.UdpServer;
import java.time.Duration;
public class Application {
public static void main(String[] args) {
Connection server =
UdpServer.create()
.wiretap(true) (1)
.bindNow(Duration.ofSeconds(30));
server.onDispose()
.block();
}
1 | Enables the wire logging |
Wire Logger formatters
Reactor Netty supports 3 different formatters:
-
AdvancedByteBufFormat#HEX_DUMP - the default
/**
* When wire logging is enabled with this format, both events and content will be logged.
* The content will be in hex format.
* <p>Examples:</p>
* <pre>
* {@code
* reactor.netty.http.HttpTests - [d5230a14, L:/0:0:0:0:0:0:0:1:60267 - R:/0:0:0:0:0:0:0:1:60269] REGISTERED
* reactor.netty.http.HttpTests - [d5230a14, L:/0:0:0:0:0:0:0:1:60267 - R:/0:0:0:0:0:0:0:1:60269] ACTIVE
* reactor.netty.http.HttpTests - [d5230a14, L:/0:0:0:0:0:0:0:1:60267 - R:/0:0:0:0:0:0:0:1:60269] READ: 145B
* +-------------------------------------------------+
* | 0 1 2 3 4 5 6 7 8 9 a b c d e f |
* +--------+-------------------------------------------------+----------------+
* |00000000| 50 4f 53 54 20 2f 74 65 73 74 2f 57 6f 72 6c 64 |POST /test/World|
* |00000010| 20 48 54 54 50 2f 31 2e 31 0d 0a 43 6f 6e 74 65 | HTTP/1.1..Conte|
* |00000020| 6e 74 2d 54 79 70 65 3a 20 74 65 78 74 2f 70 6c |nt-Type: text/pl|
* |00000030| 61 69 6e 0d 0a 75 73 65 72 2d 61 67 65 6e 74 3a |ain..user-agent:|
* |00000040| 20 52 65 61 63 74 6f 72 4e 65 74 74 79 2f 64 65 | ReactorNetty/de|
* ...
* reactor.netty.http.HttpTests - [d5230a14, L:/0:0:0:0:0:0:0:1:60267 - R:/0:0:0:0:0:0:0:1:60269] WRITE: 38B
* +-------------------------------------------------+
* | 0 1 2 3 4 5 6 7 8 9 a b c d e f |
* +--------+-------------------------------------------------+----------------+
* |00000000| 48 54 54 50 2f 31 2e 31 20 32 30 30 20 4f 4b 0d |HTTP/1.1 200 OK.|
* |00000010| 0a 63 6f 6e 74 65 6e 74 2d 6c 65 6e 67 74 68 3a |.content-length:|
* |00000020| 20 30 0d 0a 0d 0a | 0.... |
* +--------+-------------------------------------------------+----------------+
* }
* </pre>
*/
/**
* When wire logging is enabled with this format, only the events will be logged.
* <p>Examples:</p>
* <pre>
* {@code
* reactor.netty.http.HttpTests - [230d3686, L:/0:0:0:0:0:0:0:1:60241 - R:/0:0:0:0:0:0:0:1:60245] REGISTERED
* reactor.netty.http.HttpTests - [230d3686, L:/0:0:0:0:0:0:0:1:60241 - R:/0:0:0:0:0:0:0:1:60245] ACTIVE
* reactor.netty.http.HttpTests - [230d3686, L:/0:0:0:0:0:0:0:1:60241 - R:/0:0:0:0:0:0:0:1:60245] READ: 145B
* reactor.netty.http.HttpTests - [230d3686, L:/0:0:0:0:0:0:0:1:60241 - R:/0:0:0:0:0:0:0:1:60245] WRITE: 38B
* }
* </pre>
*/
/**
* When wire logging is enabled with this format, both events and content will be logged.
* The content will be in plain text format.
* <p>Examples:</p>
* <pre>
* {@code
* reactor.netty.http.HttpTests - [02c3db6c, L:/0:0:0:0:0:0:0:1:60317 - R:/0:0:0:0:0:0:0:1:60319] REGISTERED
* reactor.netty.http.HttpTests - [02c3db6c, L:/0:0:0:0:0:0:0:1:60317 - R:/0:0:0:0:0:0:0:1:60319] ACTIVE
* reactor.netty.http.HttpTests - [02c3db6c, L:/0:0:0:0:0:0:0:1:60317 - R:/0:0:0:0:0:0:0:1:60319] READ: 145B POST /test/World HTTP/1.1
* Content-Type: text/plain
* user-agent: ReactorNetty/dev
* ...
* reactor.netty.http.HttpTests - [02c3db6c, L:/0:0:0:0:0:0:0:1:60317 - R:/0:0:0:0:0:0:0:1:60319] WRITE: 38B HTTP/1.1 200 OK
* content-length: 0
* }
* </pre>
*/
When you need to change the default formatter you can configure it as follows:
import io.netty.handler.logging.LogLevel;
import reactor.netty.Connection;
import reactor.netty.transport.logging.AdvancedByteBufFormat;
import reactor.netty.udp.UdpServer;
import java.time.Duration;
public class Application {
public static void main(String[] args) {
Connection server =
UdpServer.create()
.wiretap("logger-name", LogLevel.DEBUG, AdvancedByteBufFormat.TEXTUAL) (1)
.bindNow(Duration.ofSeconds(30));
server.onDispose()
.block();
1 | Enables the wire logging, AdvancedByteBufFormat#TEXTUAL is used for printing the content. |
7.6.3. Event Loop Group
By default, the UDP server uses “Event Loop Group,” where the number of the worker threads equals the number of
processors available to the runtime on initialization (but with a minimum value of 4). When you need a different configuration,
you can use one of the LoopResource#create
methods.
The default configuration for the “Event Loop Group” is the following:
/**
* Default worker thread count, fallback to available processor
* (but with a minimum value of 4)
*/
public static final String IO_WORKER_COUNT = "reactor.netty.ioWorkerCount";
/**
* Default selector thread count, fallback to -1 (no selector thread)
*/
public static final String IO_SELECT_COUNT = "reactor.netty.ioSelectCount";
/**
* Default worker thread count for UDP, fallback to available processor
* (but with a minimum value of 4)
*/
public static final String UDP_IO_THREAD_COUNT = "reactor.netty.udp.ioThreadCount";
/**
* Default quiet period that guarantees that the disposal of the underlying LoopResources
* will not happen, fallback to 2 seconds.
*/
public static final String SHUTDOWN_QUIET_PERIOD = "reactor.netty.ioShutdownQuietPeriod";
/**
* Default maximum amount of time to wait until the disposal of the underlying LoopResources
* regardless if a task was submitted during the quiet period, fallback to 15 seconds.
*/
public static final String SHUTDOWN_TIMEOUT = "reactor.netty.ioShutdownTimeout";
/**
* Default value whether the native transport (epoll, kqueue) will be preferred,
* fallback it will be preferred when available
*/
public static final String NATIVE = "reactor.netty.native";
If you need changes to these settings, you can apply the following configuration:
import reactor.netty.Connection;
import reactor.netty.resources.LoopResources;
import reactor.netty.udp.UdpServer;
import java.time.Duration;
public class Application {
public static void main(String[] args) {
LoopResources loop = LoopResources.create("event-loop", 1, 4, true);
Connection server =
UdpServer.create()
.runOn(loop)
.bindNow(Duration.ofSeconds(30));
server.onDispose()
.block();
}
}
7.7. Metrics
The UDP server supports built-in integration with Micrometer
.
It exposes all metrics with a prefix of reactor.netty.udp.server
.
The following table provides information for the UDP server metrics:
metric name | type | description |
---|---|---|
reactor.netty.udp.server.data.received |
DistributionSummary |
Amount of the data received, in bytes |
reactor.netty.udp.server.data.sent |
DistributionSummary |
Amount of the data sent, in bytes |
reactor.netty.udp.server.errors |
Counter |
Number of errors that occurred |
These additional metrics are also available:
ByteBufAllocator
metrics
metric name | type | description |
---|---|---|
reactor.netty.bytebuf.allocator.used.heap.memory |
Gauge |
The number of bytes reserved by heap buffer allocator |
reactor.netty.bytebuf.allocator.used.direct.memory |
Gauge |
The number of bytes reserved by direct buffer allocator |
reactor.netty.bytebuf.allocator.used.heap.arenas |
Gauge |
The number of heap arenas (when |
reactor.netty.bytebuf.allocator.used.direct.arenas |
Gauge |
The number of direct arenas (when |
reactor.netty.bytebuf.allocator.used.threadlocal.caches |
Gauge |
The number of thread local caches (when |
reactor.netty.bytebuf.allocator.used.small.cache.size |
Gauge |
The size of the small cache (when |
reactor.netty.bytebuf.allocator.used.normal.cache.size |
Gauge |
The size of the normal cache (when |
reactor.netty.bytebuf.allocator.used.chunk.size |
Gauge |
The chunk size for an arena (when |
reactor.netty.bytebuf.allocator.active.heap.buffers |
Gauge |
The actual bytes consumed by in-use heap buffers (when |
reactor.netty.bytebuf.allocator.active.direct.buffers |
Gauge |
The actual bytes consumed by in-use direct buffers (when |
EventLoop
metrics
metric name | type | description |
---|---|---|
reactor.netty.eventloop.pending.tasks |
Gauge |
The number of tasks that are pending for processing on an event loop |
The following example enables that integration:
import reactor.netty.Connection;
import reactor.netty.udp.UdpServer;
import java.time.Duration;
public class Application {
public static void main(String[] args) {
Connection server =
UdpServer.create()
.metrics(true) (1)
.bindNow(Duration.ofSeconds(30));
server.onDispose()
.block();
}
}
1 | Enables the built-in integration with Micrometer |
When UDP server metrics are needed for an integration with a system other than Micrometer
or you want
to provide your own integration with Micrometer
, you can provide your own metrics recorder, as follows:
import reactor.netty.Connection;
import reactor.netty.channel.ChannelMetricsRecorder;
import reactor.netty.udp.UdpServer;
import java.net.SocketAddress;
import java.time.Duration;
public class Application {
public static void main(String[] args) {
Connection server =
UdpServer.create()
.metrics(true, CustomChannelMetricsRecorder::new) (1)
.bindNow(Duration.ofSeconds(30));
server.onDispose()
.block();
}
1 | Enables UDP server metrics and provides ChannelMetricsRecorder implementation. |
7.8. Unix Domain Sockets
The UdpServer
supports Unix Domain Datagram Sockets (UDS) when native transport is in use.
The following example shows how to use UDS support:
import io.netty.channel.unix.DomainDatagramPacket;
import io.netty.channel.unix.DomainSocketAddress;
import reactor.core.publisher.Mono;
import reactor.netty.Connection;
import reactor.netty.udp.UdpServer;
import java.io.File;
public class Application {
public static void main(String[] args) {
Connection server =
UdpServer.create()
.bindAddress(Application::newDomainSocketAddress) (1)
.handle((in, out) ->
out.sendObject(
in.receiveObject()
.map(o -> {
if (o instanceof DomainDatagramPacket) {
DomainDatagramPacket p = (DomainDatagramPacket) o;
return new DomainDatagramPacket(p.content().retain(), p.sender());
}
else {
return Mono.error(new Exception("Unexpected type of the message: " + o));
}
})))
.bindNow();
server.onDispose()
.block();
}
1 | Specifies DomainSocketAddress that will be used |
Suggest Edit to "UDP Server"
8. UDP Client
Reactor Netty provides the easy-to-use and easy-to-configure
UdpClient
.
It hides most of the Netty functionality that is required to create a UDP
client
and adds Reactive Streams backpressure.
8.1. Connecting and Disconnecting
To connect the UDP client to a given endpoint, you must create and configure a
UdpClient instance.
By default, the host is configured for localhost
and the port is 12012
.
The following example shows how to create and connect a UDP client:
import reactor.netty.Connection;
import reactor.netty.udp.UdpClient;
import java.time.Duration;
public class Application {
public static void main(String[] args) {
Connection connection =
UdpClient.create() (1)
.connectNow(Duration.ofSeconds(30)); (2)
connection.onDispose()
.block();
}
}
1 | Creates a UdpClient
instance that is ready for configuring. |
2 | Connects the client in a blocking fashion and waits for it to finish initializing. |
The returned Connection
offers a simple connection API, including disposeNow()
,
which shuts the client down in a blocking fashion.
8.1.1. Host and Port
To connect to a specific host
and port
, you can apply the following configuration to the UDP
client:
import reactor.netty.Connection;
import reactor.netty.udp.UdpClient;
import java.time.Duration;
public class Application {
public static void main(String[] args) {
Connection connection =
UdpClient.create()
.host("example.com") (1)
.port(80) (2)
.connectNow(Duration.ofSeconds(30));
connection.onDispose()
.block();
}
}
1 | Configures the host to which this client should connect |
2 | Configures the port to which this client should connect |
8.2. Eager Initialization
By default, the initialization of the UdpClient
resources happens on demand. This means that the connect
operation
absorbs the extra time needed to initialize and load:
-
the event loop group
-
the host name resolver
-
the native transport libraries (when native transport is used)
When you need to preload these resources, you can configure the UdpClient
as follows:
import reactor.core.publisher.Mono;
import reactor.netty.Connection;
import reactor.netty.udp.UdpClient;
import java.time.Duration;
public class Application {
public static void main(String[] args) {
UdpClient udpClient = UdpClient.create()
.host("example.com")
.port(80)
.handle((udpInbound, udpOutbound) -> udpOutbound.sendString(Mono.just("hello")));
udpClient.warmup() (1)
.block();
Connection connection = udpClient.connectNow(Duration.ofSeconds(30)); (2)
connection.onDispose()
.block();
}
}
1 | Initialize and load the event loop group, the host name resolver, and the native transport libraries |
2 | Host name resolution happens when connecting to the remote peer |
8.3. Writing Data
To send data to a given peer, you must attach an I/O handler.
The I/O handler has access to UdpOutbound
,
to be able to write data.
The following example shows how to send hello
:
import reactor.core.publisher.Mono;
import reactor.netty.Connection;
import reactor.netty.udp.UdpClient;
import java.time.Duration;
public class Application {
public static void main(String[] args) {
Connection connection =
UdpClient.create()
.host("example.com")
.port(80)
.handle((udpInbound, udpOutbound) -> udpOutbound.sendString(Mono.just("hello"))) (1)
.connectNow(Duration.ofSeconds(30));
connection.onDispose()
.block();
}
}
1 | Sends hello string to the remote peer. |
8.4. Consuming Data
To receive data from a given peer, you must attach an I/O handler.
The I/O handler has access to UdpInbound
,
to be able to read data.
The following example shows how to consume data:
import reactor.netty.Connection;
import reactor.netty.udp.UdpClient;
import java.time.Duration;
public class Application {
public static void main(String[] args) {
Connection connection =
UdpClient.create()
.host("example.com")
.port(80)
.handle((udpInbound, udpOutbound) -> udpInbound.receive().then()) (1)
.connectNow(Duration.ofSeconds(30));
connection.onDispose()
.block();
}
}
1 | Receives data from a given peer |
8.5. Lifecycle Callbacks
The following lifecycle callbacks are provided to let you extend the UdpClient
:
Callback | Description |
---|---|
|
Invoked after the remote address has been resolved successfully. |
|
Invoked when initializing the channel. |
|
Invoked when the channel is about to connect. |
|
Invoked after the channel has been connected. |
|
Invoked after the channel has been disconnected. |
|
Invoked when the remote address is about to be resolved. |
|
Invoked in case the remote address hasn’t been resolved successfully. |
The following example uses the doOnConnected
and doOnChannelInit
callbacks:
import io.netty.handler.codec.LineBasedFrameDecoder;
import io.netty.handler.logging.LoggingHandler;
import reactor.netty.Connection;
import reactor.netty.udp.UdpClient;
import java.time.Duration;
public class Application {
public static void main(String[] args) {
Connection connection =
UdpClient.create()
.host("example.com")
.port(80)
.doOnConnected(conn -> conn.addHandlerLast(new LineBasedFrameDecoder(8192))) (1)
.doOnChannelInit((observer, channel, remoteAddress) ->
channel.pipeline()
.addFirst(new LoggingHandler("reactor.netty.examples"))) (2)
.connectNow(Duration.ofSeconds(30));
connection.onDispose()
.block();
}
}
1 | Netty pipeline is extended with LineBasedFrameDecoder when the channel has been connected. |
2 | Netty pipeline is extended with LoggingHandler when initializing the channel. |
8.6. Connection Configuration
This section describes three kinds of configuration that you can use at the UDP level:
8.6.1. Channel Options
By default, the UDP
client is configured with the following options:
UdpClientConnect() {
this.config = new UdpClientConfig(
ConnectionProvider.newConnection(),
Collections.singletonMap(ChannelOption.AUTO_READ, false),
() -> new InetSocketAddress(NetUtil.LOCALHOST, DEFAULT_PORT));
}
If you need additional options or need to change the current options, you can apply the following configuration:
import io.netty.channel.ChannelOption;
import reactor.netty.Connection;
import reactor.netty.udp.UdpClient;
import java.time.Duration;
public class Application {
public static void main(String[] args) {
Connection connection =
UdpClient.create()
.host("example.com")
.port(80)
.option(ChannelOption.CONNECT_TIMEOUT_MILLIS, 10000)
.connectNow(Duration.ofSeconds(30));
connection.onDispose()
.block();
}
}
You can find more about Netty channel options at the following links:
8.6.2. Wire Logger
Reactor Netty provides wire logging for when the traffic between the peers needs to be inspected.
By default, wire logging is disabled.
To enable it, you must set the logger reactor.netty.udp.UdpClient
level to DEBUG
and apply the following configuration:
import reactor.netty.Connection;
import reactor.netty.udp.UdpClient;
import java.time.Duration;
public class Application {
public static void main(String[] args) {
Connection connection =
UdpClient.create()
.host("example.com")
.port(80)
.wiretap(true) (1)
.connectNow(Duration.ofSeconds(30));
connection.onDispose()
1 | Enables the wire logging |
Wire Logger formatters
Reactor Netty supports 3 different formatters:
-
AdvancedByteBufFormat#HEX_DUMP - the default
/**
* When wire logging is enabled with this format, both events and content will be logged.
* The content will be in hex format.
* <p>Examples:</p>
* <pre>
* {@code
* reactor.netty.http.HttpTests - [d5230a14, L:/0:0:0:0:0:0:0:1:60267 - R:/0:0:0:0:0:0:0:1:60269] REGISTERED
* reactor.netty.http.HttpTests - [d5230a14, L:/0:0:0:0:0:0:0:1:60267 - R:/0:0:0:0:0:0:0:1:60269] ACTIVE
* reactor.netty.http.HttpTests - [d5230a14, L:/0:0:0:0:0:0:0:1:60267 - R:/0:0:0:0:0:0:0:1:60269] READ: 145B
* +-------------------------------------------------+
* | 0 1 2 3 4 5 6 7 8 9 a b c d e f |
* +--------+-------------------------------------------------+----------------+
* |00000000| 50 4f 53 54 20 2f 74 65 73 74 2f 57 6f 72 6c 64 |POST /test/World|
* |00000010| 20 48 54 54 50 2f 31 2e 31 0d 0a 43 6f 6e 74 65 | HTTP/1.1..Conte|
* |00000020| 6e 74 2d 54 79 70 65 3a 20 74 65 78 74 2f 70 6c |nt-Type: text/pl|
* |00000030| 61 69 6e 0d 0a 75 73 65 72 2d 61 67 65 6e 74 3a |ain..user-agent:|
* |00000040| 20 52 65 61 63 74 6f 72 4e 65 74 74 79 2f 64 65 | ReactorNetty/de|
* ...
* reactor.netty.http.HttpTests - [d5230a14, L:/0:0:0:0:0:0:0:1:60267 - R:/0:0:0:0:0:0:0:1:60269] WRITE: 38B
* +-------------------------------------------------+
* | 0 1 2 3 4 5 6 7 8 9 a b c d e f |
* +--------+-------------------------------------------------+----------------+
* |00000000| 48 54 54 50 2f 31 2e 31 20 32 30 30 20 4f 4b 0d |HTTP/1.1 200 OK.|
* |00000010| 0a 63 6f 6e 74 65 6e 74 2d 6c 65 6e 67 74 68 3a |.content-length:|
* |00000020| 20 30 0d 0a 0d 0a | 0.... |
* +--------+-------------------------------------------------+----------------+
* }
* </pre>
*/
/**
* When wire logging is enabled with this format, only the events will be logged.
* <p>Examples:</p>
* <pre>
* {@code
* reactor.netty.http.HttpTests - [230d3686, L:/0:0:0:0:0:0:0:1:60241 - R:/0:0:0:0:0:0:0:1:60245] REGISTERED
* reactor.netty.http.HttpTests - [230d3686, L:/0:0:0:0:0:0:0:1:60241 - R:/0:0:0:0:0:0:0:1:60245] ACTIVE
* reactor.netty.http.HttpTests - [230d3686, L:/0:0:0:0:0:0:0:1:60241 - R:/0:0:0:0:0:0:0:1:60245] READ: 145B
* reactor.netty.http.HttpTests - [230d3686, L:/0:0:0:0:0:0:0:1:60241 - R:/0:0:0:0:0:0:0:1:60245] WRITE: 38B
* }
* </pre>
*/
/**
* When wire logging is enabled with this format, both events and content will be logged.
* The content will be in plain text format.
* <p>Examples:</p>
* <pre>
* {@code
* reactor.netty.http.HttpTests - [02c3db6c, L:/0:0:0:0:0:0:0:1:60317 - R:/0:0:0:0:0:0:0:1:60319] REGISTERED
* reactor.netty.http.HttpTests - [02c3db6c, L:/0:0:0:0:0:0:0:1:60317 - R:/0:0:0:0:0:0:0:1:60319] ACTIVE
* reactor.netty.http.HttpTests - [02c3db6c, L:/0:0:0:0:0:0:0:1:60317 - R:/0:0:0:0:0:0:0:1:60319] READ: 145B POST /test/World HTTP/1.1
* Content-Type: text/plain
* user-agent: ReactorNetty/dev
* ...
* reactor.netty.http.HttpTests - [02c3db6c, L:/0:0:0:0:0:0:0:1:60317 - R:/0:0:0:0:0:0:0:1:60319] WRITE: 38B HTTP/1.1 200 OK
* content-length: 0
* }
* </pre>
*/
When you need to change the default formatter you can configure it as follows:
import io.netty.handler.logging.LogLevel;
import reactor.netty.Connection;
import reactor.netty.transport.logging.AdvancedByteBufFormat;
import reactor.netty.udp.UdpClient;
import java.time.Duration;
public class Application {
public static void main(String[] args) {
Connection connection =
UdpClient.create()
.host("example.com")
.port(80)
.wiretap("logger-name", LogLevel.DEBUG, AdvancedByteBufFormat.TEXTUAL) (1)
.connectNow(Duration.ofSeconds(30));
1 | Enables the wire logging, AdvancedByteBufFormat#TEXTUAL is used for printing the content. |
8.6.3. Event Loop Group
By default, the UDP client uses “Event Loop Group,” where the number of the worker threads equals the number of
processors available to the runtime on initialization (but with a minimum value of 4). When you need a different configuration,
you can use one of the LoopResources
#create
methods.
The following listing shows the default configuration for the “Event Loop Group”:
/**
* Default worker thread count, fallback to available processor
* (but with a minimum value of 4)
*/
public static final String IO_WORKER_COUNT = "reactor.netty.ioWorkerCount";
/**
* Default selector thread count, fallback to -1 (no selector thread)
*/
public static final String IO_SELECT_COUNT = "reactor.netty.ioSelectCount";
/**
* Default worker thread count for UDP, fallback to available processor
* (but with a minimum value of 4)
*/
public static final String UDP_IO_THREAD_COUNT = "reactor.netty.udp.ioThreadCount";
/**
* Default quiet period that guarantees that the disposal of the underlying LoopResources
* will not happen, fallback to 2 seconds.
*/
public static final String SHUTDOWN_QUIET_PERIOD = "reactor.netty.ioShutdownQuietPeriod";
/**
* Default maximum amount of time to wait until the disposal of the underlying LoopResources
* regardless if a task was submitted during the quiet period, fallback to 15 seconds.
*/
public static final String SHUTDOWN_TIMEOUT = "reactor.netty.ioShutdownTimeout";
/**
* Default value whether the native transport (epoll, kqueue) will be preferred,
* fallback it will be preferred when available
*/
public static final String NATIVE = "reactor.netty.native";
If you need changes to the these settings, you can apply the following configuration:
import reactor.netty.Connection;
import reactor.netty.resources.LoopResources;
import reactor.netty.udp.UdpClient;
import java.time.Duration;
public class Application {
public static void main(String[] args) {
LoopResources loop = LoopResources.create("event-loop", 1, 4, true);
Connection connection =
UdpClient.create()
.host("example.com")
.port(80)
.runOn(loop)
.connectNow(Duration.ofSeconds(30));
connection.onDispose()
.block();
}
}
8.7. Metrics
The UDP client supports built-in integration with Micrometer
.
It exposes all metrics with a prefix of reactor.netty.udp.client
.
The following table provides information for the UDP client metrics:
metric name | type | description |
---|---|---|
reactor.netty.udp.client.data.received |
DistributionSummary |
Amount of the data received, in bytes |
reactor.netty.udp.client.data.sent |
DistributionSummary |
Amount of the data sent, in bytes |
reactor.netty.udp.client.errors |
Counter |
Number of errors that occurred |
reactor.netty.udp.client.connect.time |
Timer |
Time spent for connecting to the remote address |
reactor.netty.udp.client.address.resolver |
Timer |
Time spent for resolving the address |
These additional metrics are also available:
ByteBufAllocator
metrics
metric name | type | description |
---|---|---|
reactor.netty.bytebuf.allocator.used.heap.memory |
Gauge |
The number of bytes reserved by heap buffer allocator |
reactor.netty.bytebuf.allocator.used.direct.memory |
Gauge |
The number of bytes reserved by direct buffer allocator |
reactor.netty.bytebuf.allocator.used.heap.arenas |
Gauge |
The number of heap arenas (when |
reactor.netty.bytebuf.allocator.used.direct.arenas |
Gauge |
The number of direct arenas (when |
reactor.netty.bytebuf.allocator.used.threadlocal.caches |
Gauge |
The number of thread local caches (when |
reactor.netty.bytebuf.allocator.used.small.cache.size |
Gauge |
The size of the small cache (when |
reactor.netty.bytebuf.allocator.used.normal.cache.size |
Gauge |
The size of the normal cache (when |
reactor.netty.bytebuf.allocator.used.chunk.size |
Gauge |
The chunk size for an arena (when |
reactor.netty.bytebuf.allocator.active.heap.buffers |
Gauge |
The actual bytes consumed by in-use heap buffers (when |
reactor.netty.bytebuf.allocator.active.direct.buffers |
Gauge |
The actual bytes consumed by in-use direct buffers (when |
EventLoop
metrics
metric name | type | description |
---|---|---|
reactor.netty.eventloop.pending.tasks |
Gauge |
The number of tasks that are pending for processing on an event loop |
The following example enables that integration:
import reactor.netty.Connection;
import reactor.netty.udp.UdpClient;
import java.time.Duration;
public class Application {
public static void main(String[] args) {
Connection connection =
UdpClient.create()
.host("example.com")
.port(80)
.metrics(true) (1)
.connectNow(Duration.ofSeconds(30));
connection.onDispose()
.block();
}
}
1 | Enables the built-in integration with Micrometer |
When UDP client metrics are needed for an integration with a system other than Micrometer
or you want
to provide your own integration with Micrometer
, you can provide your own metrics recorder, as follows:
import reactor.netty.Connection;
import reactor.netty.channel.ChannelMetricsRecorder;
import reactor.netty.udp.UdpClient;
import java.net.SocketAddress;
import java.time.Duration;
public class Application {
public static void main(String[] args) {
Connection connection =
UdpClient.create()
.host("example.com")
.port(80)
.metrics(true, CustomChannelMetricsRecorder::new) (1)
.connectNow(Duration.ofSeconds(30));
connection.onDispose()
.block();
}
1 | Enables UDP client metrics and provides ChannelMetricsRecorder implementation. |
8.8. Unix Domain Sockets
The UdpClient
supports Unix Domain Datagram Sockets (UDS) when native transport is in use.
The following example shows how to use UDS support:
import io.netty.channel.unix.DomainSocketAddress;
import reactor.core.publisher.Mono;
import reactor.netty.Connection;
import reactor.netty.udp.UdpClient;
import java.io.File;
public class Application {
public static void main(String[] args) {
Connection connection =
UdpClient.create()
.bindAddress(Application::newDomainSocketAddress)
.remoteAddress(() -> new DomainSocketAddress("/tmp/test-server.sock")) (1)
.handle((in, out) ->
out.sendString(Mono.just("hello"))
.then(in.receive()
.asString()
.doOnNext(System.out::println)
.then()))
.connectNow();
connection.onDispose()
.block();
}
1 | Specifies DomainSocketAddress that will be used |
Suggest Edit to "UDP Client"
Appendix A: Frequently Asked Questions
This section covers the following content:
A.1. Connection to the proxy cannot be established
Netty’s HTTP proxy support always uses CONNECT
method in order to establish a tunnel to the specified proxy regardless of the scheme that is used http
or https
.
(More information: Netty enforce HTTP proxy to support HTTP CONNECT method).
Some proxies might not support CONNECT
method when the scheme is http
or might need to be configured in order to support this way of communication.
Sometimes this might be the reason for not being able to connect to the proxy. Consider checking the proxy documentation
whether it supports or needs an additional configuration in order to support CONNECT
method.
A.2. What is it meaning of the information that is prepended to every log record?
Reactor Netty adds information for the connection at the beginning of every log record (when this is possible).
There is a slight difference in the details for the connection when you use TCP
, UDP
, HTTP/1.1
or HTTP/2
.
A.2.1. TCP and UDP
In case of TCP
and UDP
, the following is added at the beginning of every log record: the id of the underlying connection, local and remote addresses.
Examples
[a1566d55, L:/[0:0:0:0:0:0:0:1]:53446 - R:/[0:0:0:0:0:0:0:1]:53444]
[a1566d55, L:/[0:0:0:0:0:0:0:1]:53446 ! R:/[0:0:0:0:0:0:0:1]:53444]
Format
[<CONNECTION_ID>, L:<LOCAL_ADDRESS> <CONNECTION_OPENED_CLOSED> R:<REMOTE_ADDRESS>]
<CONNECTION_ID>: a1566d55
<LOCAL_ADDRESS>: [0:0:0:0:0:0:0:1]:53446
<CONNECTION_OPENED_CLOSED>: - (connection opened)
! (connection closed)
<REMOTE_ADDRESS>: [0:0:0:0:0:0:0:1]:53444
A.2.2. HTTP/1.1
In case of HTTP/1.1
, the following is added at the beginning of every log record: the id of the underlying connection,
the serial number of the request received on that connection, local and remote addresses.
Examples
[a1566d55-5, L:/[0:0:0:0:0:0:0:1]:53446 - R:/[0:0:0:0:0:0:0:1]:53444]
[a1566d55-5, L:/[0:0:0:0:0:0:0:1]:53446 ! R:/[0:0:0:0:0:0:0:1]:53444]
Format
[<CONNECTION_ID>-<REQUEST_NUMBER>, L:<LOCAL_ADDRESS> <CONNECTION_OPENED_CLOSED> R:<REMOTE_ADDRESS>]
<CONNECTION_ID>: a1566d55
<REQUEST_NUMBER>: 5
<LOCAL_ADDRESS>: [0:0:0:0:0:0:0:1]:53446
<CONNECTION_OPENED_CLOSED>: - (connection opened)
! (connection closed)
<REMOTE_ADDRESS>: [0:0:0:0:0:0:0:1]:53444
A.2.3. HTTP/2
In case of HTTP/2
, the following is added at the beginning of every log record: the id of the underlying connection,
local and remote addresses, the id of the stream received on that connection.
Examples
[a1566d55, L:/[0:0:0:0:0:0:0:1]:53446 - R:/[0:0:0:0:0:0:0:1]:53444](H2 - 5)
[a1566d55, L:/[0:0:0:0:0:0:0:1]:53446 ! R:/[0:0:0:0:0:0:0:1]:53444](H2 - 5)
Format
[<CONNECTION_ID>, L:<LOCAL_ADDRESS> <CONNECTION_OPENED_CLOSED> R:<REMOTE_ADDRESS>]<STREAM_ID>
<CONNECTION_ID>: a1566d55
<LOCAL_ADDRESS>: [0:0:0:0:0:0:0:1]:53446
<CONNECTION_OPENED_CLOSED>: - (connection opened)
! (connection closed)
<REMOTE_ADDRESS>: [0:0:0:0:0:0:0:1]:53444
<STREAM_ID>: (H2 - 5)
A.3. How can I extract all log records for a particular HTTP request?
Reactor Netty adds information for the connection at the beginning of every log record (when this is possible). Use the id of the connection in order to extract all log records for a particular HTTP request. For more information see What is it meaning of the information that is prepended to every log record?
A.4. How can I debug a memory leak?
By default, Reactor Netty uses direct memory as this is more performant when there are many native I/O operations (working with sockets), as this can remove the copying operations. As allocation and deallocation are expensive operations, Reactor Netty also uses pooled buffers by default. For more information, see Reference Counted Objects.
To be able to debug memory issues with the direct memory and the pooled buffers, Netty provides a special memory leak detection mechanism.
Follow the instructions for Troubleshooting Buffer Leaks
to enable this mechanism. In addition to the instructions provided by Netty, Reactor Netty provides a special
logger (_reactor.netty.channel.LeakDetection
) that helps to identify where the memory leak might be located inside Reactor Netty
or whether Reactor Netty already forwarded the ownership of the buffers to the application/framework.
By default, this logger is disabled. To enable it, increase the log level to DEBUG
.
Another way to detect memory leaks is to monitor reactor.netty.bytebuf.allocator.active.heap.memory
and reactor.netty.bytebuf.allocator.active.direct.memory
meters:
-
The
reactor.netty.bytebuf.allocator.active.heap.memory
provides the actual bytes consumed by in-use buffers allocated from heap buffer pools -
The
reactor.netty.bytebuf.allocator.active.direct.memory
provides the actual bytes consumed by in-use buffers allocated from direct buffer pools
If the above meters are constantly growing, then it’s likely that there is a buffer memory leak.
Consider reducing the used memory when debugging memory leak issues (e.g -XX:MaxDirectMemorySize , -Xms , -Xmx ).
The less memory the application has, the sooner the memory leak will happen.
|
A.5. How can I debug "Connection prematurely closed BEFORE response"?
By default, Reactor Netty clients use connection pooling. When a connection is acquired from the connection pool, it is checked to see whether it is still open. However, the connection can be closed at any time after the acquisition. There are many reasons that can cause a connection to be closed. In most cases, the client might not send directly to the server. Instead, there might be other network components (proxies, load balancers, and so on) between them.
If, on the client side, you observe Connection prematurely closed BEFORE response
, perform the following checks to identify the reason for the connection being closed:
-
Obtain a TCP dump and check which peer sends a FIN/RST signal.
-
Check your network connection.
-
Check your Firewall and VPN.
-
Check for any proxies and load balancers.
-
Do they have some kind of idle timeout configuration (the connection is closed when there is no incoming data for a certain period of time)?
-
Do they silently drop the idle connections without sending any signal? In order to verify whether this might be the issue, you can enable the TCP keep-alive as described in the section Connection Timeout. Issues related to TCP keep-alive configuration on various load balancers were reported in the past.
-
-
Check the target server. Are there configurations related to any of the following?
-
idle timeout (the connection is closed when there is no incoming data for a certain period of time)
-
limit for buffering data in memory
-
multipart exceeds the max file size limit
-
bad request
-
Consider checking Timeout Configuration. The section describes various timeout configuration options that are available for Reactor Netty clients. Configuring a proper timeout may improve or solve issues in the communication process.