在 Spring 集成中从收集器返回的响应不一致

Question

I'm using Scatter-gather pattern and calling 3 sub-flows parallelly. Then gathering them and aggregating them. I'm trying to get the result back after aggregating. I'm getting the response as List but the two responses that are there in the list are not consistent. When I'm trying to get by doing .get(0), sometime it's giving me 1st services's response other time 2ns service's response. It's inconsistent. Kindly suggest me a way to understand the output so that I can assign it to the actual variable.

Config file

 @Configuration
    public class IntegrationConfiguration {
      @Autowired LoansServiceImpl loansService;
    
      long dbId = new SequenceGenerator().nextId();
  //   Main flow
  @Bean
  public IntegrationFlow flow() {
    return flow ->
        flow.split()
            .log()
            .channel(c -> c.executor(Executors.newCachedThreadPool()))
            .convert(LoanProvisionRequest.class)
            .scatterGather(
                scatterer ->
                    scatterer
                        .applySequence(true)
                        .recipientFlow(flow1())
                        .recipientFlow(flow2())
                        .recipientFlow(flow3()),
                gatherer -> gatherer.releaseLockBeforeSend(true))
            .log()
            .aggregate(a -> a.outputProcessor(MessageGroup::getMessages))
            .channel("output-flow");
  }
  //   flow1
  @Bean
  public IntegrationFlow flow1() {
    return integrationFlowDefination ->
        integrationFlowDefination
            .channel(c -> c.executor(Executors.newCachedThreadPool()))
            .handle(
                message -> {
                  try {
                    lionService.saveLionRequest(
                        (LionRequest) message.getPayload(), String.valueOf(dbId));
                  } catch (JsonProcessingException e) {
                    throw new RuntimeException(e);
                  }
                });
  }

  //   flow2
  @Bean
  public IntegrationFlow flow2() {
    return integrationFlowDefination ->
        integrationFlowDefination
            .channel(c -> c.executor(Executors.newCachedThreadPool()))
            .handle(
                message ->
                    lionService.getData(
                        (LionRequest) message.getPayload(), SourceSystem.PROVISION))
            .log();
  }

  //  flow3
  @Bean
  public IntegrationFlow flow3() {
    return integrationFlowDefination ->
        integrationFlowDefination
            .channel(c -> c.executor(Executors.newCachedThreadPool()))
            .handle(
                message ->
                    lionService.prepareCDRequest(
                        (LionRequest) message));
  }

  @Bean
  public MessageChannel replyChannel() {
    return MessageChannels.executor("output-flow", outputExecutor()).get();
  }

  @Bean
  public ThreadPoolTaskExecutor outputExecutor() {
    ThreadPoolTaskExecutor pool = new ThreadPoolTaskExecutor();
    pool.setCorePoolSize(4);
    pool.setMaxPoolSize(4);
    return pool;
  }
}

Gateway

@MessagingGateway
public interface LionGateway {

  @Gateway(requestChannel = "flow.input", replyChannel = "output-flow")
  List<?> echo(LionRequest lionRequest);
}

Controller

@Autowired private LionGateway lionGateway;

 @PostMapping(value = "/invoke-integration")
  public String invokeIntegrationFlow(@RequestBody LionRequest lionRequest) {
    String response1 = lionGateway.echo(lionRequest).get(0);
    String response2 = lionGateway.echo(lionRequest).get(1);
    System.out.Println("response2 ")
    System.out.Println("response1 ")

    return "response";
  }

in the Controller I have two variables ie, response1 & response2 these two values are coming as inconsistent. Help me with a better approach.

Answer 1

Since you are using executor channels, the order is simply the order in which the replies come back. The gatherer knows nothing about the downstream topology.

You will need to deal with the random order of the reply list in your code.