Package reactor.core

Class Scannable.Attr<T>

java.lang.Object

reactor.core.Scannable.Attr<T>

Type Parameters:

T - the type of data associated with an attribute

Enclosing interface:

Scannable

public static class Scannable.Attr<T>
extends Object

Base class for Scannable attributes, which all can define a meaningful default.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static enum	Scannable.Attr.RunStyle	An Enum enumerating the different styles an operator can run : their Enum.ordinal() reflects the level of confidence in their running mode

Field Summary

Fields

Modifier and Type	Field	Description
static final Scannable.Attr<Scannable>	ACTUAL	The direct dependent component downstream reference if any.
static final Scannable.Attr<Boolean>	ACTUAL_METADATA	Indicate that for some purposes a Scannable should be used as additional source of information about a contiguous Scannable in the chain.
static final Scannable.Attr<Integer>	BUFFERED	A Integer attribute implemented by components with a backlog capacity.
static final Scannable.Attr<Boolean>	CANCELLED	A Boolean attribute indicating whether or not a downstream component has interrupted consuming this scanned component, e.g., a cancelled subscription.
static final Scannable.Attr<Integer>	CAPACITY	Return an an Integer capacity when no PREFETCH is defined or when an arbitrary maximum limit is applied to the backlog capacity of the scanned component.
static final Scannable.Attr<Boolean>	DELAY_ERROR	Delay_Error exposes a Boolean whether the scanned component actively supports error delaying if it manages a backlog instead of fast error-passing which might drop pending backlog.
static final Scannable.Attr<Throwable>	ERROR	a Throwable attribute which indicate an error state if the scanned component keeps track of it.
static final Scannable.Attr<Long>	LARGE_BUFFERED	Similar to BUFFERED, but reserved for operators that can hold a backlog of items that can grow beyond Integer.MAX_VALUE.
static final Scannable.Attr<String>	LIFTER	LIFTER attribute exposes name of the lifter function.
static final Scannable.Attr<String>	NAME	An arbitrary name given to the operator component.
static final Scannable.Attr<Scannable>	PARENT	Parent key exposes the direct upstream relationship of the scanned component.
static final Scannable.Attr<Integer>	PREFETCH	Prefetch is an Integer attribute defining the rate of processing in a component which has capacity to request and hold a backlog of data.
static final Scannable.Attr<Long>	REQUESTED_FROM_DOWNSTREAM	A Long attribute exposing the current pending demand of a downstream component.
static final Scannable.Attr<Scannable>	RUN_ON	A key that links a Scannable to another Scannable it runs on.
static final Scannable.Attr<Scannable.Attr.RunStyle>	RUN_STYLE	An Scannable.Attr.RunStyle enum attribute indicating whether or not an operator continues to operate on the same thread.
static final Scannable.Attr<Stream<Tuple2<String,String>>>	TAGS	A Stream of Tuple2 representing key/value pairs for tagged components.
static final Scannable.Attr<Boolean>	TERMINATED	A Boolean attribute indicating whether or not an upstream component terminated this scanned component.

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	Attr(@Nullable T defaultValue)
protected	Attr(@Nullable T defaultValue, @Nullable Function<Object,? extends T> safeConverter)

Method Summary

Modifier and Type	Method	Description
@Nullable T	defaultValue()	Meaningful and always applicable default value for the attribute, returned instead of null when a specific value hasn't been defined for a component.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

ACTUAL

public static final Scannable.Attr<Scannable> ACTUAL

The direct dependent component downstream reference if any. Operators in Flux/Mono for instance delegate to a target Subscriber, which is going to be the actual chain navigated with this reference key. Subscribers are not always Scannable, but this attribute will convert these raw results to an unavailable scan object in this case.

A reference chain downstream can be navigated via Scannable.actuals().

ACTUAL_METADATA

public static final Scannable.Attr<Boolean> ACTUAL_METADATA

Indicate that for some purposes a Scannable should be used as additional source of information about a contiguous Scannable in the chain.

For example Scannable.steps() uses this to collate the stepName of an assembly trace to its wrapped operator (the one before it in the assembly chain).

BUFFERED

public static final Scannable.Attr<Integer> BUFFERED

A Integer attribute implemented by components with a backlog capacity. It will expose current queue size or similar related to user-provided held data. Note that some operators and processors CAN keep a backlog larger than Integer.MAX_VALUE, in which case the Attr LARGE_BUFFERED should be used instead. Such operators will attempt to serve a BUFFERED query but will return Integer.MIN_VALUE when actual buffer size is oversized for int.

CAPACITY

public static final Scannable.Attr<Integer> CAPACITY

Return an an Integer capacity when no PREFETCH is defined or when an arbitrary maximum limit is applied to the backlog capacity of the scanned component. Integer.MAX_VALUE signal unlimited capacity.

Note: This attribute usually resolves to a constant value.

CANCELLED

public static final Scannable.Attr<Boolean> CANCELLED

A Boolean attribute indicating whether or not a downstream component has interrupted consuming this scanned component, e.g., a cancelled subscription. Note that it differs from TERMINATED which is intended for "normal" shutdown cycles.

DELAY_ERROR

public static final Scannable.Attr<Boolean> DELAY_ERROR

Delay_Error exposes a Boolean whether the scanned component actively supports error delaying if it manages a backlog instead of fast error-passing which might drop pending backlog.

Note: This attribute usually resolves to a constant value.

ERROR

public static final Scannable.Attr<Throwable> ERROR

a Throwable attribute which indicate an error state if the scanned component keeps track of it.

LARGE_BUFFERED

public static final Scannable.Attr<Long> LARGE_BUFFERED

Similar to BUFFERED, but reserved for operators that can hold a backlog of items that can grow beyond Integer.MAX_VALUE. These operators will also answer to a BUFFERED query up to the point where their buffer is actually too large, at which point they'll return Integer.MIN_VALUE, which serves as a signal that this attribute should be used instead. Defaults to null.

Flux.flatMap, Flux.filterWhen and Flux.window (with overlap) are known to use this attribute.

NAME

public static final Scannable.Attr<String> NAME

An arbitrary name given to the operator component. Defaults to null.

PARENT

public static final Scannable.Attr<Scannable> PARENT

Parent key exposes the direct upstream relationship of the scanned component. It can be a Publisher source to an operator, a Subscription to a Subscriber (main flow if ambiguous with inner Subscriptions like flatMap), a Scheduler to a Worker. These types are not always Scannable, but this attribute will convert such raw results to an unavailable scan object in this case.

Scannable.parents() can be used to navigate the parent chain.

RUN_ON

public static final Scannable.Attr<Scannable> RUN_ON

A key that links a Scannable to another Scannable it runs on. Usually exposes a link between an operator/subscriber and its Scheduler.Worker or Scheduler, provided these are Scannable. Will return UNAVAILABLE_SCAN if the supporting execution is not Scannable or NULL_SCAN if the operator doesn't define a specific runtime.

PREFETCH

public static final Scannable.Attr<Integer> PREFETCH

Prefetch is an Integer attribute defining the rate of processing in a component which has capacity to request and hold a backlog of data. It usually maps to a component capacity when no arbitrary CAPACITY is set. Integer.MAX_VALUE signal unlimited capacity and therefore unbounded demand.

Note: This attribute usually resolves to a constant value.

REQUESTED_FROM_DOWNSTREAM

public static final Scannable.Attr<Long> REQUESTED_FROM_DOWNSTREAM

A Long attribute exposing the current pending demand of a downstream component. Note that Long.MAX_VALUE indicates an unbounded (push-style) demand as specified in Subscription.request(long).

TERMINATED

public static final Scannable.Attr<Boolean> TERMINATED

A Boolean attribute indicating whether or not an upstream component terminated this scanned component. e.g. a post onComplete/onError subscriber. By opposition to CANCELLED which determines if a downstream component interrupted this scanned component.

TAGS

public static final Scannable.Attr<Stream<Tuple2<String,String>>> TAGS

A Stream of Tuple2 representing key/value pairs for tagged components. Defaults to null.

RUN_STYLE

public static final Scannable.Attr<Scannable.Attr.RunStyle> RUN_STYLE

An Scannable.Attr.RunStyle enum attribute indicating whether or not an operator continues to operate on the same thread. Each value provides a different degree of guarantee from weakest Scannable.Attr.RunStyle.UNKNOWN to strongest Scannable.Attr.RunStyle.SYNC. Defaults to Scannable.Attr.RunStyle.UNKNOWN.

LIFTER

public static final Scannable.Attr<String> LIFTER

LIFTER attribute exposes name of the lifter function. It is calculated as Object.toString() of a function passed to the Operators.lift(java.util.function.BiFunction<reactor.core.Scannable, ? super reactor.core.CoreSubscriber<? super O>, ? extends reactor.core.CoreSubscriber<? super I>>) or Operators.liftPublisher(java.util.function.BiFunction<org.reactivestreams.Publisher, ? super reactor.core.CoreSubscriber<? super O>, ? extends reactor.core.CoreSubscriber<? super I>>). Defaults to null.

Constructor Details

Attr

protected Attr(@Nullable T defaultValue)

Attr

protected Attr(@Nullable T defaultValue,
 @Nullable Function<Object,? extends T> safeConverter)

Method Details

defaultValue

public @Nullable T defaultValue()

Meaningful and always applicable default value for the attribute, returned instead of null when a specific value hasn't been defined for a component. null if no sensible generic default is available.

Returns:

the default value applicable to all components or null if none.