Package org.apache.pekko.stream.javadsl

Class RestartFlow

java.lang.Object
org.apache.pekko.stream.javadsl.RestartFlow
public class RestartFlow extends Object
A RestartFlow wraps a Flow that gets restarted when it completes or fails.

They are useful for graphs that need to run for longer than the Flow can necessarily guarantee it will, for example, for Flow streams that depend on a remote server that may crash or become partitioned. The RestartFlow ensures that the graph can continue running while the Flow restarts.

  • Constructor Details

    • RestartFlow

      public RestartFlow()

  • Method Details

    • withBackoff

      public static <In, Out> Flow<In,Out,NotUsed> withBackoff(RestartSettings settings, Creator<Flow<In,Out,?>> flowFactory)
      Wrap the given Flow with a Flow that will restart it when it fails or complete using an exponential backoff.

      This Flow will not cancel, complete or emit a failure, until the opposite end of it has been cancelled or completed. Any termination by the Flow before that time will be handled by restarting it as long as maxRestarts is not reached. Any termination signals sent to this Flow however will terminate the wrapped Flow, if it's running, and then the Flow will be allowed to terminate without being restarted.

      The restart process is inherently lossy, since there is no coordination between cancelling and the sending of messages. A termination signal from either end of the wrapped Flow will cause the other end to be terminated, and any in transit messages will be lost. During backoff, this Flow will backpressure.

      This uses the same exponential backoff algorithm as pekko.pattern.BackoffOpts.

      Parameters:
      settings - RestartSettings defining restart configuration
      flowFactory - A factory for producing the Flow to wrap.

    • onFailuresWithBackoff

      public static <In, Out> Flow<In,Out,NotUsed> onFailuresWithBackoff(RestartSettings settings, Creator<Flow<In,Out,?>> flowFactory)
      Wrap the given Flow with a Flow that will restart only when it fails that restarts using an exponential backoff.

      This new Flow will not emit failures. Any failure by the original Flow (the wrapped one) before that time will be handled by restarting it as long as maxRestarts is not reached. However, any termination signals, completion or cancellation sent to this Flow will terminate the wrapped Flow, if it's running, and then the Flow will be allowed to terminate without being restarted.

      The restart process is inherently lossy, since there is no coordination between cancelling and the sending of messages. A termination signal from either end of the wrapped Flow will cause the other end to be terminated, and any in transit messages will be lost. During backoff, this Flow will backpressure.

      This uses the same exponential backoff algorithm as pekko.pattern.BackoffOpts.

      Parameters:
      settings - RestartSettings defining restart configuration
      flowFactory - A factory for producing the Flow to wrap.