Package reactor.util.retry

Class Retry

java.lang.Object

reactor.util.retry.Retry

Direct Known Subclasses:

RetryBackoffSpec, RetrySpec

public abstract class Retry
extends Object

Base abstract class for a strategy to decide when to retry given a companion Flux of Retry.RetrySignal, for use with Flux.retryWhen(Retry) and Mono.retryWhen(Retry). Also provides access to configurable built-in strategies via static factory methods:

• indefinitely()
• max(long)
• maxInARow(long)
• fixedDelay(long, Duration)
• backoff(long, Duration)

Users are encouraged to provide either concrete custom Retry strategies or builders that produce such concrete Retry. The RetrySpec returned by e.g. max(long) is a good inspiration for a fluent approach that generates a Retry at each step and uses immutability/copy-on-write to enable sharing of intermediate steps (that can thus be considered templates).

Author:

Simon Baslé

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static interface	Retry.RetrySignal	State used in Flux.retryWhen(Retry) and Mono.retryWhen(Retry), providing the Throwable that caused the source to fail as well as counters keeping track of retries.

Field Summary

Fields

Modifier and Type	Field	Description
final ContextView	retryContext

Constructor Summary

Constructors

Modifier	Constructor	Description
	Retry()
protected	Retry(ContextView retryContext)

Method Summary

Modifier and Type	Method	Description
static RetryBackoffSpec	backoff(long maxAttempts, Duration minBackoff)	A RetryBackoffSpec preconfigured for exponential backoff strategy with jitter, given a maximum number of retry attempts and a minimum Duration for the backoff.
static RetryBackoffSpec	fixedDelay(long maxAttempts, Duration fixedDelay)	A RetryBackoffSpec preconfigured for fixed delays (min backoff equals max backoff, no jitter), given a maximum number of retry attempts and the fixed Duration for the backoff.
static final Retry	from(Function<Flux<Retry.RetrySignal>,? extends Publisher<?>> function)	A wrapper around Function to provide Retry by using lambda expressions.
abstract Publisher<?>	generateCompanion(Flux<Retry.RetrySignal> retrySignals)	Generates the companion publisher responsible for reacting to incoming Retry.RetrySignal emissions, effectively deciding when to retry.
static RetrySpec	indefinitely()	A RetrySpec preconfigured for the most simplistic retry strategy: retry immediately and indefinitely (similar to Flux.retry()).
static RetrySpec	max(long max)	A RetrySpec preconfigured for a simple strategy with maximum number of retry attempts.
static RetrySpec	maxInARow(long maxInARow)	A RetrySpec preconfigured for a simple strategy with maximum number of retry attempts over subsequent transient errors.
ContextView	retryContext()	Return the user provided context that was set at construction time.
static final Retry	withThrowable(Function<Flux<Throwable>,? extends Publisher<?>> function)	An adapter for Flux of Throwable-based Function to provide Retry from a legacy retryWhen Function.

Methods inherited from class java.lang.Object

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

Field Details

retryContext

public final ContextView retryContext

Constructor Details

Retry

public Retry()

Retry

protected Retry(ContextView retryContext)

Method Details

generateCompanion

public abstract Publisher<?> generateCompanion(Flux<Retry.RetrySignal> retrySignals)

Generates the companion publisher responsible for reacting to incoming Retry.RetrySignal emissions, effectively deciding when to retry.

When the source signals an error, that onError signal will be suppressed. Its Throwable will instead be attached to a Retry.RetrySignal, immediately emitted on the retrySignals publisher. Right after that emission, request(1) is called on the companion publisher.

The response to that request decides if a retry should be made. Thus, the outer publisher will wait until a signal is emitted by the companion publisher, making it possible to delay retry attempts.

Any onNext emitted by the companion publisher triggers a retry, onError will fail the outer publisher and onComplete will complete the outer publisher (effectively suppressing the original error/Throwable).

As an example, the simplest form of retry companion would be to return the incoming Flux of Retry.RetrySignal without modification. This would render a retry strategy that immediately retries, forever.

Parameters:

retrySignals - the errors from the outer publisher as Retry.RetrySignal objects, containing the Throwable causing the error as well as retry counter metadata.

Returns:

the companion publisher responsible for reacting to incoming Retry.RetrySignal emissions, effectively deciding when to retry.

retryContext

public ContextView retryContext()

Return the user provided context that was set at construction time.

Returns:

the user provided context that will be accessible via Retry.RetrySignal.retryContextView().

backoff

public static RetryBackoffSpec backoff(long maxAttempts,
 Duration minBackoff)

A RetryBackoffSpec preconfigured for exponential backoff strategy with jitter, given a maximum number of retry attempts and a minimum Duration for the backoff.

Parameters:

maxAttempts - the maximum number of retry attempts to allow

minBackoff - the minimum Duration for the first backoff

Returns:

the exponential backoff spec for further configuration

See Also:

• RetryBackoffSpec.maxAttempts(long)
• RetryBackoffSpec.minBackoff(Duration)

fixedDelay

public static RetryBackoffSpec fixedDelay(long maxAttempts,
 Duration fixedDelay)

A RetryBackoffSpec preconfigured for fixed delays (min backoff equals max backoff, no jitter), given a maximum number of retry attempts and the fixed Duration for the backoff.

Note that calling RetryBackoffSpec.minBackoff(Duration) or RetryBackoffSpec.maxBackoff(Duration) would switch back to an exponential backoff strategy.

Parameters:

maxAttempts - the maximum number of retry attempts to allow

fixedDelay - the Duration of the fixed delays

Returns:

the fixed delays spec for further configuration

See Also:

• RetryBackoffSpec.maxAttempts(long)
• RetryBackoffSpec.minBackoff(Duration)
• RetryBackoffSpec.maxBackoff(Duration)

max

public static RetrySpec max(long max)

A RetrySpec preconfigured for a simple strategy with maximum number of retry attempts.

Parameters:

max - the maximum number of retry attempts to allow

Returns:

the max attempt spec for further configuration

See Also:

• RetrySpec.maxAttempts(long)

maxInARow

public static RetrySpec maxInARow(long maxInARow)

A RetrySpec preconfigured for a simple strategy with maximum number of retry attempts over subsequent transient errors. An Subscriber.onNext(Object) between errors resets the counter (see RetrySpec.transientErrors(boolean)).

Parameters:

maxInARow - the maximum number of retry attempts to allow in a row, reset by successful onNext

Returns:

the max in a row spec for further configuration

See Also:

• RetrySpec.maxAttempts(long)
• RetrySpec.transientErrors(boolean)

indefinitely

public static RetrySpec indefinitely()

A RetrySpec preconfigured for the most simplistic retry strategy: retry immediately and indefinitely (similar to Flux.retry()).

Returns:

the retry indefinitely spec for further configuration

from

public static final Retry from(Function<Flux<Retry.RetrySignal>,? extends Publisher<?>> function)

A wrapper around Function to provide Retry by using lambda expressions.

Parameters:

function - the Function representing the desired Retry strategy as a lambda

Returns:

the Retry strategy adapted from the Function

withThrowable

public static final Retry withThrowable(Function<Flux<Throwable>,? extends Publisher<?>> function)

An adapter for Flux of Throwable-based Function to provide Retry from a legacy retryWhen Function.

Parameters:

function - the Function representing the desired Retry strategy as a lambda

Returns:

the Retry strategy adapted from the Function