如何正确使用分散聚集模式？

时间：2018-10-04 15:57:37

标签： java spring spring-integration spring-integration-dsl

在谈到Spring Integration时，我还是一个新手，我正尝试使用IntetrationFlowDefinition.scatterGather()无济于事。总体思路是：

  • 以String作为输入
  • 使用分隔符使用空格字符将其标记化
  • 将每个令牌发送到一组服务，每个服务都返回一个值
  • 汇总每个服务的响应
  • 聚合以前对List的响应
  • 将列表转换为单个String

我正在使用消息传递网关作为输入/输出：

@MessagingGateway(name = "gateway")
public interface TestGateway {

  @Gateway(requestChannel = "input")
  String process(String input);

}

并通过以下方式调用它：

final TestGateway gateway = (TestGateway) ctx.getBean("gateway");
System.out.println(gateway.process("this is a test"));

我的IntegrationFlow是：

@Bean
public IntegrationFlow soutFlow() {
  return f -> f.handle(m -> System.out.println(m.toString()));
}

@Bean
public IntegrationFlow flow() {
  return IntegrationFlows.from("input")
    .split(s -> s.delimiters(" "))
    .wireTap(soutFlow())
    .scatterGather(
      sc -> sc.recipientFlow(m -> true, f1 -> f1.handle((p, h) -> p + " - flow 1").wireTap(soutFlow()))
        .recipientFlow(m -> true, f2 -> f2.handle((p, h) -> p + " - flow 2").wireTap(soutFlow()))
        .applySequence(true),
      ga -> ga.outputProcessor(mg -> mg.getMessages()
        .stream()
        .map(m -> m.getPayload().toString())
        .collect(Collectors.joining(", "))),
      sg -> sg.gatherTimeout(1_000))
    .wireTap(soutFlow())
    .aggregate()
    .wireTap(soutFlow())
    .transform((List<String> source) -> source.stream()
      .map(s -> "- " + s)
      .collect(Collectors.joining("\n")))
    .get();
}

我希望看到输出格式如下：

- this - flow 1, this - flow 2
- is - flow 1, is - flow 2
- a - flow 1, a - flow 2
- test - flow 1, test - flow 2

不幸的是，这不起作用，收集器总是在1秒后超时。窃听调试输出显示以下消息：

GenericMessage [payload=this, headers={replyChannel=org.springframework.messaging.core.GenericMessagingTemplate$TemporaryReplyChannel@649725e3, sequenceNumber=1, errorChannel=org.springframework.messaging.core.GenericMessagingTemplate$TemporaryReplyChannel@649725e3, sequenceSize=4, correlationId=7c9653a7-55eb-72e4-ff74-62b10782cc3b, id=6c81a1ce-9a7c-83c3-3b69-7fb2f8b3112c, timestamp=1538668173435}]
GenericMessage [payload=this - flow 1, headers={replyChannel=org.springframework.integration.channel.FixedSubscriberChannel@78aea4b9, sequenceNumber=1, gatherResultChannel=ac418949-6ade-4db5-bd4c-3cbbbb7e9a49:1, sequenceDetails=[[7c9653a7-55eb-72e4-ff74-62b10782cc3b, 1, 4]], errorChannel=org.springframework.messaging.core.GenericMessagingTemplate$TemporaryReplyChannel@649725e3, sequenceSize=2, correlationId=8d29aea7-3ec7-2c15-5b92-fbb0af002a3f, id=7ca4de30-f801-ad14-6452-249c85e9ab36, timestamp=1538668173446}]
GenericMessage [payload=this - flow 2, headers={replyChannel=org.springframework.integration.channel.FixedSubscriberChannel@78aea4b9, sequenceNumber=2, gatherResultChannel=ac418949-6ade-4db5-bd4c-3cbbbb7e9a49:1, sequenceDetails=[[7c9653a7-55eb-72e4-ff74-62b10782cc3b, 1, 4]], errorChannel=org.springframework.messaging.core.GenericMessagingTemplate$TemporaryReplyChannel@649725e3, sequenceSize=2, correlationId=8d29aea7-3ec7-2c15-5b92-fbb0af002a3f, id=71b22112-8e7b-c2c5-057f-2a91c49af8c8, timestamp=1538668173446}]
GenericMessage [payload=is, headers={replyChannel=org.springframework.messaging.core.GenericMessagingTemplate$TemporaryReplyChannel@649725e3, sequenceNumber=2, errorChannel=org.springframework.messaging.core.GenericMessagingTemplate$TemporaryReplyChannel@649725e3, sequenceSize=4, correlationId=7c9653a7-55eb-72e4-ff74-62b10782cc3b, id=9da2f181-82de-d50e-51bb-229a3e32b998, timestamp=1538668174448}]
GenericMessage [payload=is - flow 1, headers={replyChannel=org.springframework.integration.channel.FixedSubscriberChannel@78aea4b9, sequenceNumber=1, gatherResultChannel=ac418949-6ade-4db5-bd4c-3cbbbb7e9a49:2, sequenceDetails=[[7c9653a7-55eb-72e4-ff74-62b10782cc3b, 2, 4]], errorChannel=org.springframework.messaging.core.GenericMessagingTemplate$TemporaryReplyChannel@649725e3, sequenceSize=2, correlationId=0abfd6a8-713d-e0cb-bc59-a111a85429df, id=d5102417-f6c2-cbac-197a-b9c4f3f51a74, timestamp=1538668174448}]
GenericMessage [payload=is - flow 2, headers={replyChannel=org.springframework.integration.channel.FixedSubscriberChannel@78aea4b9, sequenceNumber=2, gatherResultChannel=ac418949-6ade-4db5-bd4c-3cbbbb7e9a49:2, sequenceDetails=[[7c9653a7-55eb-72e4-ff74-62b10782cc3b, 2, 4]], errorChannel=org.springframework.messaging.core.GenericMessagingTemplate$TemporaryReplyChannel@649725e3, sequenceSize=2, correlationId=0abfd6a8-713d-e0cb-bc59-a111a85429df, id=d9b31390-d3d1-9b61-43fc-45c06ac86931, timestamp=1538668174449}]
GenericMessage [payload=a, headers={replyChannel=org.springframework.messaging.core.GenericMessagingTemplate$TemporaryReplyChannel@649725e3, sequenceNumber=3, errorChannel=org.springframework.messaging.core.GenericMessagingTemplate$TemporaryReplyChannel@649725e3, sequenceSize=4, correlationId=7c9653a7-55eb-72e4-ff74-62b10782cc3b, id=f109f368-6859-ac8d-0e0c-3beb563f9594, timestamp=1538668175451}]
GenericMessage [payload=a - flow 1, headers={replyChannel=org.springframework.integration.channel.FixedSubscriberChannel@78aea4b9, sequenceNumber=1, gatherResultChannel=ac418949-6ade-4db5-bd4c-3cbbbb7e9a49:3, sequenceDetails=[[7c9653a7-55eb-72e4-ff74-62b10782cc3b, 3, 4]], errorChannel=org.springframework.messaging.core.GenericMessagingTemplate$TemporaryReplyChannel@649725e3, sequenceSize=2, correlationId=0e347381-a6e2-891a-72ff-c862565d6a1e, id=e0270063-6e19-5827-7674-21fa047ab11d, timestamp=1538668175451}]
GenericMessage [payload=a - flow 2, headers={replyChannel=org.springframework.integration.channel.FixedSubscriberChannel@78aea4b9, sequenceNumber=2, gatherResultChannel=ac418949-6ade-4db5-bd4c-3cbbbb7e9a49:3, sequenceDetails=[[7c9653a7-55eb-72e4-ff74-62b10782cc3b, 3, 4]], errorChannel=org.springframework.messaging.core.GenericMessagingTemplate$TemporaryReplyChannel@649725e3, sequenceSize=2, correlationId=0e347381-a6e2-891a-72ff-c862565d6a1e, id=b08aab99-10ce-4dac-2f3c-b48b4514fd35, timestamp=1538668175451}]
GenericMessage [payload=test, headers={replyChannel=org.springframework.messaging.core.GenericMessagingTemplate$TemporaryReplyChannel@649725e3, sequenceNumber=4, errorChannel=org.springframework.messaging.core.GenericMessagingTemplate$TemporaryReplyChannel@649725e3, sequenceSize=4, correlationId=7c9653a7-55eb-72e4-ff74-62b10782cc3b, id=52feeb27-8da4-70c4-889e-f482d2922e40, timestamp=1538668176453}]
GenericMessage [payload=test - flow 1, headers={replyChannel=org.springframework.integration.channel.FixedSubscriberChannel@78aea4b9, sequenceNumber=1, gatherResultChannel=ac418949-6ade-4db5-bd4c-3cbbbb7e9a49:4, sequenceDetails=[[7c9653a7-55eb-72e4-ff74-62b10782cc3b, 4, 4]], errorChannel=org.springframework.messaging.core.GenericMessagingTemplate$TemporaryReplyChannel@649725e3, sequenceSize=2, correlationId=53e7fd2c-d3a4-0c0a-1296-2a14ef5e90ab, id=9152e603-e436-c0a4-abde-1f7e5ae654bf, timestamp=1538668176454}]
GenericMessage [payload=test - flow 2, headers={replyChannel=org.springframework.integration.channel.FixedSubscriberChannel@78aea4b9, sequenceNumber=2, gatherResultChannel=ac418949-6ade-4db5-bd4c-3cbbbb7e9a49:4, sequenceDetails=[[7c9653a7-55eb-72e4-ff74-62b10782cc3b, 4, 4]], errorChannel=org.springframework.messaging.core.GenericMessagingTemplate$TemporaryReplyChannel@649725e3, sequenceSize=2, correlationId=53e7fd2c-d3a4-0c0a-1296-2a14ef5e90ab, id=a7357efd-d34a-6a05-159e-5860e3bc5281, timestamp=1538668176454}]

我肯定会遗漏一些明显的东西，但是当涉及到良好的Java DSL示例时，Spring文档非常稀缺。

更新：

实际上，使用wireTap()确实会影响流程。我已经删除它并设置了一些断点。看来收集器正在正确处理分散的和已处理的消息，问题似乎出在进一步将它们发送到下游。例外是：

org.springframework.messaging.MessagingException: Failed to handle Message; nested exception is org.springframework.messaging.core.DestinationResolutionException:
 failed to look up MessageChannel with name '27cf1bec-7e06-424e-80f8-9f2f67ebaf87:2' in the BeanFactory.;
 nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No bean named '27cf1bec-7e06-424e-80f8-9f2f67ebaf87:2' available,
 failedMessage=GenericMessage [payload=is - flow 1, is - flow 2, headers={replyChannel=org.springframework.integration.channel.FixedSubscriberChannel@4bafe935, sequenceNumber=2, gatherResultChannel=27cf1bec-7e06-424e-80f8-9f2f67ebaf87:2, sequenceDetails=[[2baa7135-5c02-932f-6b5d-cfd4052a965b, 2, 4]], errorChannel=org.springframework.messaging.core.GenericMessagingTemplate$TemporaryReplyChannel@87b5b49, sequenceSize=2, correlationId=c04f280d-83b7-74e9-a0a6-0f89efdf795c, id=ffec13cf-531e-0721-1484-e8b26b705330, timestamp=1538735548924}]

我想这些中间通道是在使用IntegrationFlow时由Spring自动创建的。不是吗？

1 个答案:

答案 0 :(得分：1)

问题是收集器设置不正确/不正确。我的假设是，如果分散收集的输入是单个String（标记词），则输出也应该是单个String。不幸的是，以这种方式创建的聚合器未正确还原序列/相关标头，导致下一行的聚合器无限期地等待完成该组。提供null收集器将还原默认行为。不利的一面是，分散收集的输出现在是List。可以通过在下一个聚合器之前放置一个将列表变平的转换器来轻松缓解这种情况。下面的工作代码：

@Bean
public IntegrationFlow flow() {
  return IntegrationFlows.from("input")
    .split(s -> s.delimiters(" "))
    .scatterGather(
      sc -> sc
        .applySequence(true)
        .recipientFlow(m -> true, f1 -> f1.handle((p, h) -> p + " - flow 1"))
        .recipientFlow(m -> true, f2 -> f2.handle((p, h) -> p + " - flow 2")),
      null
    )
    .transform((List<String> l) -> l.stream().collect(Collectors.joining(", ")))
    .aggregate()
    .transform((List<String> source) -> source.stream()
      .map(s -> "- " + s)
      .collect(Collectors.joining("\n")))
    .get();
}

现在输出的结果与预期的一样：

- this - flow 1, this - flow 2
- is - flow 1, is - flow 2
- a - flow 1, a - flow 2
- test - flow 1, test - flow 2
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