Package reactor.util.retry

Class RetrySpec

java.lang.Object
reactor.util.retry.Retry
reactor.util.retry.RetrySpec
public final class RetrySpec extends Retry
A simple count-based Retry strategy with configurable features. Use Retry.max(long), Retry.maxInARow(long) or Retry.indefinitely() to obtain a preconfigured instance to start with.

Only errors that match the filter(Predicate) are retried (by default all), up to maxAttempts(long) times.

When the maximum attempt of retries is reached, a runtime exception is propagated downstream which can be pinpointed with Exceptions.isRetryExhausted(Throwable). The cause of the last attempt's failure is attached as said retryExhausted exception's cause. This can be customized with onRetryExhaustedThrow(BiFunction).

Additionally, to help dealing with bursts of transient errors in a long-lived Flux as if each burst had its own attempt counter, one can choose to set transientErrors(boolean) to true. The comparison to maxAttempts(long) will then be done with the number of subsequent attempts that failed without an onNext in between.

The RetrySpec is copy-on-write and as such can be stored as a "template" and further configured by different components without a risk of modifying the original configuration.

Author:
Simon Baslé

  • Field Details

  • Method Details

    • withRetryContext

      public RetrySpec withRetryContext(ContextView retryContext)
      Set the user provided context that can be used to manipulate state on retries.
      Parameters:
      retryContext - a new snapshot of user provided data
      Returns:
      a new copy of the RetrySpec which can either be further configured or used as Retry

    • maxAttempts

      public RetrySpec maxAttempts(long maxAttempts)
      Set the maximum number of retry attempts allowed. 1 meaning "1 retry attempt": the original subscription plus an extra re-subscription in case of an error, but no more.
      Parameters:
      maxAttempts - the new retry attempt limit
      Returns:
      a new copy of the RetrySpec which can either be further configured or used as a Retry

    • filter

      public RetrySpec filter(Predicate<? super Throwable> errorFilter)
      Set the Predicate that will filter which errors can be retried. Exceptions that don't pass the predicate will be propagated downstream and terminate the retry sequence. Defaults to allowing retries for all exceptions.
      Parameters:
      errorFilter - the predicate to filter which exceptions can be retried
      Returns:
      a new copy of the RetrySpec which can either be further configured or used as Retry

    • modifyErrorFilter

      public RetrySpec modifyErrorFilter(Function<Predicate<Throwable>,Predicate<? super Throwable>> predicateAdjuster)
      Allows to augment a previously set Predicate with a new condition to allow retries of some exception or not. This can typically be used with Predicate.and(Predicate) to combine existing predicate(s) with a new one.

      For example: 

      
 //given
 RetrySpec retryTwiceIllegalArgument = Retry.max(2)
     .filter(e -> e instanceof IllegalArgumentException);

 RetrySpec retryTwiceIllegalArgWithCause = retryTwiceIllegalArgument.modifyErrorFilter(old ->
     old.and(e -> e.getCause() != null));
      Parameters:
      predicateAdjuster - a Function that returns a new Predicate given the currently in place Predicate (usually deriving from the old predicate).
      Returns:
      a new copy of the RetrySpec which can either be further configured or used as Retry

    • doBeforeRetry

      public RetrySpec doBeforeRetry(Consumer<Retry.RetrySignal> doBeforeRetry)
      Add synchronous behavior to be executed before the retry trigger is emitted in the companion publisher. This should not be blocking, as the companion publisher might be executing in a shared thread.
      Parameters:
      doBeforeRetry - the synchronous hook to execute before retry trigger is emitted
      Returns:
      a new copy of the RetrySpec which can either be further configured or used as Retry
      See Also:

    • doAfterRetry

      public RetrySpec doAfterRetry(Consumer<Retry.RetrySignal> doAfterRetry)
      Add synchronous behavior to be executed after the retry trigger is emitted in the companion publisher. This should not be blocking, as the companion publisher might be publishing events in a shared thread.
      Parameters:
      doAfterRetry - the synchronous hook to execute after retry trigger is started
      Returns:
      a new copy of the RetrySpec which can either be further configured or used as Retry
      See Also:

    • doBeforeRetryAsync

      public RetrySpec doBeforeRetryAsync(Function<Retry.RetrySignal,Mono<Void>> doAsyncBeforeRetry)
      Add asynchronous behavior to be executed before the current retry trigger in the companion publisher, thus delaying the resulting retry trigger with the additional Mono.
      Parameters:
      doAsyncBeforeRetry - the asynchronous hook to execute before original retry trigger is emitted
      Returns:
      a new copy of the RetrySpec which can either be further configured or used as Retry

    • doAfterRetryAsync

      public RetrySpec doAfterRetryAsync(Function<Retry.RetrySignal,Mono<Void>> doAsyncAfterRetry)
      Add asynchronous behavior to be executed after the current retry trigger in the companion publisher, thus delaying the resulting retry trigger with the additional Mono.
      Parameters:
      doAsyncAfterRetry - the asynchronous hook to execute after original retry trigger is emitted
      Returns:
      a new copy of the RetrySpec which can either be further configured or used as Retry

    • onRetryExhaustedThrow

      public RetrySpec onRetryExhaustedThrow(BiFunction<RetrySpec,Retry.RetrySignal,Throwable> retryExhaustedGenerator)
      Set the generator for the Exception to be propagated when the maximum amount of retries is exhausted. By default, throws an Exceptions.retryExhausted(String, Throwable) with the message reflecting the total attempt index, transient attempt index and maximum retry count. The cause of the last Retry.RetrySignal is also added as the exception's cause.
      Parameters:
      retryExhaustedGenerator - the Function that generates the Throwable for the last Retry.RetrySignal
      Returns:
      a new copy of the RetrySpec which can either be further configured or used as Retry

    • transientErrors

      public RetrySpec transientErrors(boolean isTransientErrors)
      Set the transient error mode, indicating that the strategy being built should use Retry.RetrySignal.totalRetriesInARow() rather than Retry.RetrySignal.totalRetries(). Transient errors are errors that could occur in bursts but are then recovered from by a retry (with one or more onNext signals) before another error occurs.

      In the case of a simple count-based retry, this means that the maxAttempts(long) is applied to each burst individually.

      Parameters:
      isTransientErrors - true to activate transient mode
      Returns:
      a new copy of the RetrySpec which can either be further configured or used as Retry

    • generateCompanion

      public Flux<Long> generateCompanion(Flux<Retry.RetrySignal> flux)
      Description copied from class: Retry
      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.

      Specified by:
      generateCompanion in class Retry
      Parameters:
      flux - 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.