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Doc onFailureWithBackoff (#28356)

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Christopher Batey 2020-03-03 09:18:34 +00:00 • committed by GitHub
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akka-docs/src/test/scala/docs/stream/operators/source/Restart.scala Normal file
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/*
* Copyright (C) 2009-2020 Lightbend Inc. <https://www.lightbend.com>
*/
package docs.stream.operators.source
import akka.NotUsed
import akka.actor.ActorSystem
import akka.stream.KillSwitches
import akka.stream.UniqueKillSwitch
import akka.stream.scaladsl.Keep
import akka.stream.scaladsl.RestartSource
import akka.stream.scaladsl.Sink
import scala.concurrent.duration._
import scala.util.control.NoStackTrace
// #imports
import akka.stream.scaladsl.Source
// #imports
object Restart extends App {
implicit val system: ActorSystem = ActorSystem()
onRestartWitFailureKillSwitch()
case class CantConnectToDatabase(msg: String) extends RuntimeException(msg) with NoStackTrace
def onRestartWithBackoffInnerFailure(): Unit = {
//#restart-failure-inner-failure
// could throw if for example it used a database connection to get rows
val flakySource: Source[() => Int, NotUsed] =
Source(List(() => 1, () => 2, () => 3, () => throw CantConnectToDatabase("darn")))
val forever =
RestartSource.onFailuresWithBackoff(minBackoff = 1.second, maxBackoff = 10.seconds, 0.1)(() => flakySource)
forever.runWith(Sink.foreach(nr => system.log.info("{}", nr())))
// logs
//[INFO] [12/10/2019 13:51:58.300] [default-akka.test.stream-dispatcher-7] [akka.actor.ActorSystemImpl(default)] 1
//[INFO] [12/10/2019 13:51:58.301] [default-akka.test.stream-dispatcher-7] [akka.actor.ActorSystemImpl(default)] 2
//[INFO] [12/10/2019 13:51:58.302] [default-akka.test.stream-dispatcher-7] [akka.actor.ActorSystemImpl(default)] 3
//[WARN] [12/10/2019 13:51:58.310] [default-akka.test.stream-dispatcher-7] [RestartWithBackoffSource(akka://default)] Restarting graph due to failure. stack_trace: (docs.stream.operators.source.Restart$CantConnectToDatabase: darn)
// --> 1 second gap
//[INFO] [12/10/2019 13:51:59.379] [default-akka.test.stream-dispatcher-8] [akka.actor.ActorSystemImpl(default)] 1
//[INFO] [12/10/2019 13:51:59.382] [default-akka.test.stream-dispatcher-8] [akka.actor.ActorSystemImpl(default)] 2
//[INFO] [12/10/2019 13:51:59.383] [default-akka.test.stream-dispatcher-8] [akka.actor.ActorSystemImpl(default)] 3
//[WARN] [12/10/2019 13:51:59.386] [default-akka.test.stream-dispatcher-8] [RestartWithBackoffSource(akka://default)] Restarting graph due to failure. stack_trace: (docs.stream.operators.source.Restart$CantConnectToDatabase: darn)
//--> 2 second gap
//[INFO] [12/10/2019 13:52:01.594] [default-akka.test.stream-dispatcher-8] [akka.actor.ActorSystemImpl(default)] 1
//[INFO] [12/10/2019 13:52:01.595] [default-akka.test.stream-dispatcher-8] [akka.actor.ActorSystemImpl(default)] 2
//[INFO] [12/10/2019 13:52:01.595] [default-akka.test.stream-dispatcher-8] [akka.actor.ActorSystemImpl(default)] 3
//[WARN] [12/10/2019 13:52:01.596] [default-akka.test.stream-dispatcher-8] [RestartWithBackoffSource(akka://default)] Restarting graph due to failure. stack_trace: (docs.stream.operators.source.Restart$CantConnectToDatabase: darn)
//#restart-failure-inner-failure
}
def onRestartWithBackoffInnerComplete() {
//#restart-failure-inner-complete
val finiteSource = Source.tick(1.second, 1.second, "tick").take(3)
val forever = RestartSource.onFailuresWithBackoff(1.second, 10.seconds, 0.1)(() => finiteSource)
forever.runWith(Sink.foreach(println))
// prints
// tick
// tick
// tick
//#restart-failure-inner-complete
}
def onRestartWitFailureKillSwitch(): Unit = {
//#restart-failure-inner-complete-kill-switch
val flakySource: Source[() => Int, NotUsed] =
Source(List(() => 1, () => 2, () => 3, () => throw CantConnectToDatabase("darn")))
val stopRestarting: UniqueKillSwitch =
RestartSource
.onFailuresWithBackoff(1.second, 10.seconds, 0.1)(() => flakySource)
.viaMat(KillSwitches.single)(Keep.right)
.toMat(Sink.foreach(nr => println(s"Nr ${nr()}")))(Keep.left)
.run()
//... from some where else
// stop the source from restarting
stopRestarting.shutdown()
//#restart-failure-inner-complete-kill-switch
}
}