为什么在使用Java DSL时必须在入站webflux网关上使用。fluxtransform(F->f)？

Question

org.springframework.integration.MessageTimeoutException: failed to receive JMS response within timeout of: 5000ms
    at org.springframework.integration.jms.JmsOutboundGateway.handleRequestMessage(JmsOutboundGateway.java:741) ~[spring-integration-jms-5.3.2.RELEASE.jar:5.3.2.RELEASE]
    Suppressed: reactor.core.publisher.FluxOnAssembly$OnAssemblyException:

null

场景
我创建了一个使用四个网关的路由，用于在远程计算机上发出web请求的相当复杂的设置，但我

集成流程1：

入站webflux网关->出站jms网关

  @Bean
  public IntegrationFlow step1() {
    // request-reply pattern using the jms outbound gateway
    var gateway = Jms.outboundGateway(jmsConnectionFactory)
        .requestDestination("inboundWebfluxQueue")
        .replyDestination("outboundWebfluxQueue")
        .correlationKey("JMSCorrelationID");

    // send a request to jms, wait for the reply and return message payload as response
    return IntegrationFlows.from(webfluxServer("/example/webflux"))
        // won't work consistently without the next line
        .fluxTransform(f -> f)
        .handle(gateway).get();
  }

  @Bean
  public IntegrationFlow step2_using_webflux() {
    var gateway = WebFlux.outboundGateway("http://localhost:8080/actuator/health")
        .httpMethod(HttpMethod.GET)
        .expectedResponseType(String.class)
        // ignore headers
        .mappedResponseHeaders();

    return IntegrationFlows.from(jmsInboundGateway())
        // use webflux outbound gateway to send the request to the TEST_URL
        .handle(gateway).get();
  }

Answer 1

另一种方法是使用.channel(MessageChannels.flux())而不是.fluxtransform(f->f)。这样，我们实际上给WebFlux容器带来了一个反压力，使其在请求事件循环中等待可用的插槽。

因此，我们只是向JMS队列发送不尊重的反压力，而另一边的JMS消费者无法跟上。另外，我们在内部向同一个Netty服务器发送一个请求，再次为这些内部请求获取一个事件循环插槽。

如果您感兴趣，我编写了一个单元测试，看看是怎么回事：

@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.DEFINED_PORT)
public class IntegrationApplicationTests {


    @Autowired
    private TestRestTemplate template;

    @Test
    void testSpringIntegrationWebFlux() {
        var executor = new ThreadPoolTaskExecutor();
        executor.setCorePoolSize(100);
        executor.setWaitForTasksToCompleteOnShutdown(true);
        executor.setAwaitTerminationSeconds(10);
        executor.afterPropertiesSet();

        var numberOfExecutions = new AtomicInteger();

        for (var i = 0; i < 100; i++) {
            executor.execute(() -> {
                var responseEntity = this.template.getForEntity("/example/webflux", String.class);
                if (responseEntity.getStatusCode().is2xxSuccessful()) {
                    numberOfExecutions.getAndIncrement();
                }
            });
        }

        executor.shutdown();

        assertThat(numberOfExecutions.get()).isEqualTo(100);
    }

}