Spring Cloud 函數和死信交換

Question

我正在嘗試使用 RabbitMQ 編寫一個反應式 Spring Cloud Function 服務，它將消耗一個隊列並生成一個交換。

我有2個問題。

1. 為什么我在日志中收到以下錯誤。
2. 我將如何使用 doOnError 拒絕？ doOnError 只能訪問 throwable，而不能訪問執行拒絕的消息。

這是應用程序代碼。 它是從這個問題Spring Reactive Stream - Unexpected Shutdown復制而來的

@SpringBootApplication
public class StreamApplication {

  public static void main(String[] args) {
    SpringApplication.runStreamApplication args);
  }

  @Bean
  public Function<Flux<Message<String>>, Flux<Message<String>>> transform() {

    return inbound -> inbound.map(msg -> {
      try {
        System.out.println("ACKING MESSAGE");
        Channel channel = msg.getHeaders().get(AmqpHeaders.CHANNEL, Channel.class);
        channel.basicAck(msg.getHeaders().get(AmqpHeaders.DELIVERY_TAG, Long.class), false);
      }
      catch (IOException e) {
        e.printStackTrace();
      }
      return msg;
    });
  }
}

這是 application.yml。 它有 2 個不同的綁定器用於從隊列傳入和傳出到交換。

spring:
  cloud:
    stream:
      override-cloud-connectors: true
      rabbit:
        bindings:
          events-processor:
            producer:
              bindQueue: false
              declareExchange: false
              routing-key-expression: headers.eventType
          events:
            consumer:
              acknowledge-mode: MANUAL   
              prefetch: 10
              #auto-bind-dlq: false
              dead-letter-exchange: dead-letter-exchange
              bindQueue: false
              declareExchange: false
      function:
        definition: transform
        bindings:
          transform-in-0: events
          transform-out-0: events-processor
      bindings:
        events:
          destination: queue
          binder: consumerrabbit
          group: events-processor
        events-processor:
          destination: activity-events
          binder: producerrabbit
      binders:
        producerrabbit:
          defaultCandidate: false
          inheritEnvironment: false
          type: rabbit
          environment:
            spring:
              rabbitmq:
                host: host
                port: port
                username: username
                password: password
                virtual-host: virtual-host
        consumerrabbit:
          defaultCandidate: true
          inheritEnvironment: false
          type: rabbit
          environment:
            spring:
              rabbitmq:
                host: host
                port: port
                username: username
                password: password
                virtual-host: virtual-host

以下是啟動和應用程序接收事件時的日志。 我不確定為什么在啟動期間頻道有訂閱者，但是一旦收到消息，它就會說它沒有訂閱者。

2020-09-07 12:02:04.076  INFO 10652 --- [           main] o.s.c.s.m.DirectWithAttributesChannel    : Channel 'application-1.events' has 1 subscriber(s).
2020-09-07 18:02:08.848  INFO 10652 --- [           main] o.s.c.s.m.DirectWithAttributesChannel    : Channel 'application-1.events-processor' has 1 subscriber(s).
2020-09-07 12:02:05.081  INFO 10652 --- [           main] o.s.i.monitor.IntegrationMBeanExporter   : Registering MessageChannel events
2020-09-07 12:02:05.145  INFO 10652 --- [           main] o.s.i.monitor.IntegrationMBeanExporter   : Registering MessageChannel errorChannel
2020-09-07 12:02:05.178  INFO 10652 --- [           main] o.s.i.monitor.IntegrationMBeanExporter   : Registering MessageChannel events-processor
...................other startup log messages...............
2020-09-07 18:05:09.896  INFO 10652 --- [nts-processor-1] o.s.c.s.m.DirectWithAttributesChannel    : Channel 'application-1.events' has 0 subscriber(s).
ACKING MESSAGE
2020-09-07 18:05:12.900 ERROR 10652 --- [nts-processor-1] o.s.integration.handler.LoggingHandler   : org.springframework.messaging.MessageDeliveryException: Dispatcher has no subscribers for channel 'application-1.events'.; nested exception is org.springframework.integration.MessageDispatchingException: Dispatcher has no subscribers, failedMessage=GenericMessage [payload={
  "data": {
  
  }
}, headers={amqp_receivedDeliveryMode=NON_PERSISTENT, amqp_receivedExchange=source, amqp_deliveryTag=1, deliveryAttempt=3, amqp_consumerQueue=source.events-processor, amqp_channel=Cached Rabbit Channel: AMQChannel(amqp:), conn: Proxy@43e869ea Shared Rabbit Connection: SimpleConnection@213451a4 [delegate=amqp:], amqp_redelivered=false, id=35cdfa7f-7f75-5502-aede-6ec9569145f0, amqp_consumerTag=amq.ctag-Z87p6nKN4PLJKDbZQpXnVw, sourceData=(Body:'[B@20dc391b(byte[401])' MessageProperties [headers={}, contentLength=0, receivedDeliveryMode=NON_PERSISTENT, redelivered=false, receivedExchange=source, receivedRoutingKey=, deliveryTag=1, consumerTag=amq.ctag-Z87p6nKN4PLJKDbZQpXnVw, consumerQueue=source.events-processor]), contentType=application/json, timestamp=1599501912897}], failedMessage=GenericMessage [payload={
  "data": {
  
  }
}, headers={amqp_receivedDeliveryMode=NON_PERSISTENT, amqp_receivedExchange=source, amqp_deliveryTag=1, deliveryAttempt=3, amqp_consumerQueue=source.events-processor, amqp_channel=Cached Rabbit Channel: AMQChannel(amqp://H), conn: Proxy@43e869ea Shared Rabbit Connection: SimpleConnection@213451a4 [delegate=amqp://], amqp_redelivered=false, id=35cdfa7f-7f75-5502-aede-6ec9569145f0, amqp_consumerTag=amq.ctag-Z87p6nKN4PLJKDbZQpXnVw, sourceData=(Body:'[B@20dc391b(byte[401])' MessageProperties [headers={}, contentLength=0, receivedDeliveryMode=NON_PERSISTENT, redelivered=false, receivedExchange=source, receivedRoutingKey=, deliveryTag=1, consumerTag=amq.ctag-Z87p6nKN4PLJKDbZQpXnVw, consumerQueue=source.events-processor]), contentType=application/json, timestamp=1599501912897}]

Answer 1

弄清楚如何讓函數在失敗時向 DLQ 發送消息。 我還添加了一個消費者，因為它們是相關的。

我相信我們需要確認或拒絕消息，但是在拒絕時我們想要返回 Flux.empty() 以便沒有任何內容發布到下游交換。

代碼拒絕任何以失敗作為有效負載的消息，並確認任何其他消息。

@SpringBootApplication
public class DemoApplication {

  public static void main(String[] args) {
    SpringApplication.run(DemoApplication.class, args);
  }

  @Bean
  public Function<Flux<Message<String>>, Flux<Message<String>>> transform() {
    return inbound -> inbound.flatMap(msg -> {
      try {
        Channel channel = msg.getHeaders().get(AmqpHeaders.CHANNEL, Channel.class);
        Long deliveryTag = msg.getHeaders().get(AmqpHeaders.DELIVERY_TAG, Long.class);

        if (msg.getPayload().startsWith("fail")) {
          channel.basicReject(deliveryTag, false);
        } else {
          channel.basicAck(deliveryTag, false);
          return Flux.just(msg);
        }
      } catch (IOException e) {
        e.printStackTrace();
      }

      return Flux.empty();
    });
  }

  @Bean
  public Consumer<Flux<Message<String>>> consumer() {
    return inbound -> inbound
        .map(msg -> {
          try {
            Channel channel = msg.getHeaders().get(AmqpHeaders.CHANNEL, Channel.class);
            Long deliveryTag = msg.getHeaders().get(AmqpHeaders.DELIVERY_TAG, Long.class);

            if (msg.getPayload().startsWith("fail")) {
              channel.basicReject(deliveryTag, false);
            } else {
              channel.basicAck(deliveryTag, false);
            }
          } catch (IOException e) {
            e.printStackTrace();
          }
          return msg.getPayload();
        })
        .subscribe(System.out::println);
  }
}

spring:
  profiles: consumer
  cloud:
    stream:
      function:
        definition: consumer
      bindings:
        consumer-in-0:
          destination: consumer
          group: queue
      rabbit:
        bindings:
          consumer-in-0:
            consumer:
              acknowledge-mode: MANUAL
              autoBindDlq: true
              declareDlx: true
              bindQueue: true
              deadLetterExchange: dead-letter-exchange
              prefetch: 10
---
spring:
  profiles: processor
  cloud:
    stream:
      function:
        definition: transform
      bindings:
        transform-in-0:
          destination: processorIn
          group: queue
        transform-out-0:
          destination: processorOut
      rabbit:
        bindings:
          transform-in-0:
            consumer:
              acknowledge-mode: MANUAL
              autoBindDlq: true
              declareDlx: true
              bindQueue: true
              deadLetterExchange: dead-letter-exchange
              prefetch: 10
          transform-out-0:
            producer:
              bindQueue: true
              declareExchange: true