为什么Spring Integration故障转移没有显示异常

Question

I have some problem with Spring Integration dispatcher's failover that should show me Exception if my Message Handler fails.

I have simple Spring integration context:

<int:gateway default-request-channel="inboundChannel"
             service-interface="com.some.gateway.PrinterGateway"/>

    <int:channel id="inboundChannel">
        <int:dispatcher failover="false"/>
    </int:channel>

    <!--first Message Handler (broken)-->    
    <bean id="printService" class="com.some.service.PrinterService"/>

    <int:service-activator input-channel="inboundChannel"
                           method="print"
                           ref="printService"/>

    <!--second Message Handler-->
    <bean id="uppercasePrintService"
          class="com.some.service.UppercasePrinterService"/>

    <int:service-activator input-channel="inboundChannel"
                           method="printUppercase"
                           ref="uppercasePrintService"/>

And my broken Message Handler class:

public class PrinterService {

    public void print(Message<String> message) {
        throw new RuntimeException("This is error");
    }
}

1. Can you explain me why my failover don't work?
2. Why RuntimeException is skipped and message was delivered to the next handler?

Answer 1

It works fine for me.

It's not clear what you are trying to achieve; perhaps you misunderstand the load balancing?

By default, the load balancing strategy is round-robin, which means the first message will go to the failing endpoint; the second will go to the good endpoint. Messages will alternate.

19:23:16.867 [main] DEBUG org.springframework.integration.channel.DirectChannel - preSend on channel 'org.springframework.integration.channel.DirectChannel@1794d431', message: GenericMessage [payload=foo, headers={id=9c3b1493-0a9a-e324-6da3-262079677ed0, timestamp=1494199396867}]
org.springframework.messaging.MessageDeliveryException: failed to send Message to channel 'null'; nested exception is java.lang.RuntimeException: foo, failedMessage=GenericMessage [payload=foo, headers={id=9c3b1493-0a9a-e324-6da3-262079677ed0, timestamp=1494199396867}]
    at org.springframework.integration.channel.AbstractMessageChannel.send(AbstractMessageChannel.java:449)
    at org.springframework.integration.channel.AbstractMessageChannel.send(AbstractMessageChannel.java:373)
    at com.example.So43836561Application.main(So43836561Application.java:16)
Caused by: java.lang.RuntimeException: foo
    at com.example.So43836561Application.lambda$0(So43836561Application.java:13)
    at com.example.So43836561Application$$Lambda$1/1121454968.handleMessage(Unknown Source)
    at org.springframework.integration.dispatcher.UnicastingDispatcher.doDispatch(UnicastingDispatcher.java:160)
    at org.springframework.integration.dispatcher.UnicastingDispatcher.dispatch(UnicastingDispatcher.java:121)
    at org.springframework.integration.channel.AbstractSubscribableChannel.doSend(AbstractSubscribableChannel.java:89)
    at org.springframework.integration.channel.AbstractMessageChannel.send(AbstractMessageChannel.java:423)
    ... 2 more
19:23:18.875 [main] DEBUG org.springframework.integration.channel.DirectChannel - preSend on channel 'org.springframework.integration.channel.DirectChannel@1794d431', message: GenericMessage [payload=bar, headers={id=90aaa16c-a8c1-9162-ba8f-532fa3201c7f, timestamp=1494199398875}]
Second Service: GenericMessage [payload=bar, headers={id=90aaa16c-a8c1-9162-ba8f-532fa3201c7f, timestamp=1494199398875}]
19:23:18.876 [main] DEBUG org.springframework.integration.channel.DirectChannel - postSend (sent=true) on channel 'org.springframework.integration.channel.DirectChannel@1794d431', message: GenericMessage [payload=bar, headers={id=90aaa16c-a8c1-9162-ba8f-532fa3201c7f, timestamp=1494199398875}]

If you use a NONE load balancing strategy, all messages will go to the failing one.

19:26:38.005 [main] DEBUG org.springframework.integration.channel.DirectChannel - preSend on channel 'org.springframework.integration.channel.DirectChannel@7d9d1a19', message: GenericMessage [payload=foo, headers={id=6a69efe9-dbbd-c79b-41a9-6964fd4c8ccc, timestamp=1494199598004}]
org.springframework.messaging.MessageDeliveryException: failed to send Message to channel 'null'; nested exception is java.lang.RuntimeException: foo, failedMessage=GenericMessage [payload=foo, headers={id=6a69efe9-dbbd-c79b-41a9-6964fd4c8ccc, timestamp=1494199598004}]
    at org.springframework.integration.channel.AbstractMessageChannel.send(AbstractMessageChannel.java:449)
    at org.springframework.integration.channel.AbstractMessageChannel.send(AbstractMessageChannel.java:373)
    at com.example.So43836561Application.main(So43836561Application.java:16)
Caused by: java.lang.RuntimeException: foo
    at com.example.So43836561Application.lambda$0(So43836561Application.java:13)
    at com.example.So43836561Application$$Lambda$1/2009787198.handleMessage(Unknown Source)
    at org.springframework.integration.dispatcher.UnicastingDispatcher.doDispatch(UnicastingDispatcher.java:160)
    at org.springframework.integration.dispatcher.UnicastingDispatcher.dispatch(UnicastingDispatcher.java:121)
    at org.springframework.integration.channel.AbstractSubscribableChannel.doSend(AbstractSubscribableChannel.java:89)
    at org.springframework.integration.channel.AbstractMessageChannel.send(AbstractMessageChannel.java:423)
    ... 2 more
19:26:40.009 [main] DEBUG org.springframework.integration.channel.DirectChannel - preSend on channel 'org.springframework.integration.channel.DirectChannel@7d9d1a19', message: GenericMessage [payload=bar, headers={id=9428a10e-3a17-79d5-e4bd-731fc88ef0fe, timestamp=1494199600008}]
Exception in thread "main" org.springframework.messaging.MessageDeliveryException: failed to send Message to channel 'null'; nested exception is java.lang.RuntimeException: foo, failedMessage=GenericMessage [payload=bar, headers={id=9428a10e-3a17-79d5-e4bd-731fc88ef0fe, timestamp=1494199600008}]
    at org.springframework.integration.channel.AbstractMessageChannel.send(AbstractMessageChannel.java:449)
    at org.springframework.integration.channel.AbstractMessageChannel.send(AbstractMessageChannel.java:373)
    at com.example.So43836561Application.main(So43836561Application.java:22)
Caused by: java.lang.RuntimeException: foo
    at com.example.So43836561Application.lambda$0(So43836561Application.java:13)
    at com.example.So43836561Application$$Lambda$1/2009787198.handleMessage(Unknown Source)
    at org.springframework.integration.dispatcher.UnicastingDispatcher.doDispatch(UnicastingDispatcher.java:160)
    at org.springframework.integration.dispatcher.UnicastingDispatcher.dispatch(UnicastingDispatcher.java:121)
    at org.springframework.integration.channel.AbstractSubscribableChannel.doSend(AbstractSubscribableChannel.java:89)
    at org.springframework.integration.channel.AbstractMessageChannel.send(AbstractMessageChannel.java:423)
    ... 2 more

If that's not the problem, perhaps you have a second channel bean, with the same id that's configured differently?

Regardless, turning on DEBUG logging for org.springframework.integration will show you what's going on.

EDIT

Since you are using an async gateway (returns Future<?> ) you need to examine the result to get the exception...

@Override
public void run(ApplicationArguments applicationArguments) throws Exception {
    List<Future<Message<String>>> futures = new ArrayList<>();
    for (int i = 0; i < 10; i++) {
        Message<String> message = MessageBuilder.withPayload("Some payload that created for message id: " + i)
                .build();
        log.info("Sending message " + i);
        futures.add(gateway.print(message));
    }
    futures.forEach(f -> {
        try {
            System.out.println(f.get());
        }
        catch (ExecutionException e) {
            System.out.println(e.getCause().getMessage());
        }
        catch (InterruptedException e) {
            Thread.currentThread().interrupt();
        }
    });
}

and

public String printUppercase(Message<String> message) {
    log.info(message.getPayload().toUpperCase());
    return message.getPayload().toUpperCase();
}

result:

This is error
GenericMessage [payload=SOME PAYLOAD THAT CREATED FOR MESSAGE ID: 1, headers={id=229ad2ee-f424-61da-a9bc-a631de9bd5d0, timestamp=1494360966556}]
GenericMessage [payload=SOME PAYLOAD THAT CREATED FOR MESSAGE ID: 2, headers={id=7e2c45c4-2c7b-f3f3-243d-56d9de33375f, timestamp=1494360966556}]
This is error
This is error
This is error
GenericMessage [payload=SOME PAYLOAD THAT CREATED FOR MESSAGE ID: 6, headers={id=79f4ef60-9dea-60f3-3972-a9eefde67ebf, timestamp=1494360966556}]
GenericMessage [payload=SOME PAYLOAD THAT CREATED FOR MESSAGE ID: 7, headers={id=626d1347-e5bd-ec4c-b153-71174cc7f18d, timestamp=1494360966556}]
This is error