失败时优雅地重启 Reactive-Kafka Consumer Stream

Question

问题 当我重新启动/完成/停止流时，旧的消费者不会死/关机：

[INFO ] a.a.RepointableActorRef -
  Message [akka.kafka.KafkaConsumerActor$Internal$Stop$] 
  from Actor[akka://ufo-sightings/deadLetters]
  to Actor[akka://ufo-sightings/system/kafka-consumer-1#1896610594]
  was not delivered. [1] dead letters encountered.

说明 我正在构建一个从 Kafka 主题接收消息并通过 HTTP 请求将消息发送到外部服务的服务。

1. 与外部服务的连接可能断开，我的服务需要重试请求。

2. 此外，如果 Stream 中出现错误，则需要重新启动整个 Stream。

3. 最后，有时我不需要流及其对应的 Kafka-consumer，我想关闭整个流

所以我有一个流：

Consumer.committableSource(customizedSettings, subscriptions)
  .flatMapConcat(sourceFunction)
  .toMat(Sink.ignore)
  .run

http请求在sourceFunction发送

我遵循了新文档中的新 Kafka Consumer Restart 说明

  RestartSource.withBackoff(
      minBackoff = 20.seconds,
      maxBackoff = 5.minutes,
      randomFactor = 0.2 ) { () =>
          Consumer.committableSource(customizedSettings, subscriptions)
            .watchTermination() {
                case (consumerControl, streamComplete) =>
                  logger.info(s" Started Watching Kafka consumer id = ${consumer.id} termination: is shutdown: ${consumerControl.isShutdown}, is f completed: ${streamComplete.isCompleted}")
                  consumerControl.isShutdown.map(_ => logger.info(s"Shutdown of consumer finally happened id = ${consumer.id} at ${DateTime.now}"))
                  streamComplete
                    .flatMap { _ =>
                      consumerControl.shutdown().map(_ -> logger.info(s"3.consumer id = ${consumer.id} SHUTDOWN at ${DateTime.now} GRACEFULLY:CLOSED FROM UPSTREAM"))
                    }
                    .recoverWith {
                      case _ =>
                        consumerControl.shutdown().map(_ -> logger.info(s"3.consumer id = ${consumer.id} SHUTDOWN at ${DateTime.now} ERROR:CLOSED FROM UPSTREAM"))
                    }
             }
            .flatMapConcat(sourceFunction)
      }
      .viaMat(KillSwitches.single)(Keep.right)
      .toMat(Sink.ignore)(Keep.left)
      .run

打开了一个issue，在一个复杂的 Akka 流中讨论了这个非终止消费者，但还没有解决方案。

是否有强制终止 Kafka Consumer 的解决方法

Answer 1

如何将消费者包装在一个 Actor 中并注册一个 KillSwitch，请参阅：https://doc.akka.io/docs/akka/2.5/stream/stream-dynamic.html#dynamic-stream-handling

然后在 Actor postStop 方法中，您可以终止流。 通过将 Actor 包装在 BackoffSupervisor 中，您可以获得指数退避。

示例演员：https://github.com/tradecloud/kafka-akka-extension/blob/master/src/main/scala/nl/tradecloud/kafka/KafkaSubscriberActor.scala#L27