[doc] Document message broker related events published [SPR-11672]

[spring-projects-issues]

Prashant Deva opened SPR-11672 and commented

if you use .enableStompBrokerRelay() and you don't have a msg queue running, the logs get bombard by this exception every few mileseconds.

org.springframework.messaging.MessageDeliveryException: Message broker is not active.
INFO [LineHandler-1] [stderr] at org.springframework.messaging.simp.stomp.StompBrokerRelayMessageHandler.handleMessageInternal(StompBrokerRelayMessageHandler.java:378)
INFO [LineHandler-1] [stderr] at org.springframework.messaging.simp.broker.AbstractBrokerMessageHandler.handleMessage(AbstractBrokerMessageHandler.java:171)
INFO [LineHandler-1] [stderr] at org.springframework.messaging.support.ExecutorSubscribableChannel.sendInternal(ExecutorSubscribableChannel.java:64)
INFO [LineHandler-1] [stderr] at org.springframework.messaging.support.AbstractMessageChannel.send(AbstractMessageChannel.java:116)
INFO [LineHandler-1] [stderr] at org.springframework.messaging.support.AbstractMessageChannel.send(AbstractMessageChannel.java:98)
INFO [LineHandler-1] [stderr] at org.springframework.messaging.simp.SimpMessagingTemplate.doSend(SimpMessagingTemplate.java:129)
INFO [LineHandler-1] [stderr] at org.springframework.messaging.simp.SimpMessagingTemplate.doSend(SimpMessagingTemplate.java:48)
INFO [LineHandler-1] [stderr] at org.springframework.messaging.core.AbstractMessageSendingTemplate.send(AbstractMessageSendingTemplate.java:93)
INFO [LineHandler-1] [stderr] at org.springframework.messaging.core.AbstractMessageSendingTemplate.convertAndSend(AbstractMessageSendingTemplate.java:146)
INFO [LineHandler-1] [stderr] at org.springframework.messaging.core.AbstractMessageSendingTemplate.convertAndSend(AbstractMessageSendingTemplate.java:112)
INFO [LineHandler-1] [stderr] at org.springframework.messaging.core.AbstractMessageSendingTemplate.convertAndSend(AbstractMessageSendingTemplate.java:106)
INFO [LineHandler-1] [stderr] at com.dripstat.dripcast.GlobalScoreFirebase$1.onDataChange(GlobalScoreFirebase.java:49) 

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Affects: 4.0.3

[spring-projects-issues]

Rossen Stoyanchev commented

You need to subscribe to receive BrokerAvailabilityEvent by implementing ApplicationListener<BrokerAvailabilityEvent> from the component sending messages. See for example the QuoteService in the stock portfolio sample.

[spring-projects-issues]

Rossen Stoyanchev commented

Modified title (was "Exception bombarding when external queue is not active")

[spring-projects-issues]

Rossen Stoyanchev commented

The events include BrokerAvailability, SessionConnectEvent, SessionConnectedEvent, and SessionDisconnectEvent.

[spring-projects-issues]

Prashant Deva commented

thing is, it should not throw exceptions. if the broker is not present, then it should simply fire an event. but filling the logs with exceptions makes no sense

[spring-projects-issues]

Prashant Deva commented

why is this marked as a documentation bug? Is bombarding the logs with exceptions expected behavior?

[spring-projects-issues]

Rossen Stoyanchev commented

Is bombarding the logs with exceptions expected behavior?

Are you certain it is the the framework that's doing that? We raise a MessageDeliveryException but we don't log it and we don't usually log exceptions that are propagated up the stack. I'm pretty sure it is your application that needs to be improved. Here is some more background that is not obvious and the reason this is a documentation task.

It is a design choice to raise an exception when sending a message to the broker through the SimpMessagingTemplate. Since the brokerChannel does so synchronously (by default at least) it basically means that the code sending the message has a chance to deal with the exception. If the messages were instead handed off and sent asynchronously some additional mechanism would be required to know if the send succeeded or not. So this is meant to keep things simple with regards to sending messages within the application.

In addition the broker publishes the BrokerAvailabilityEvent and your code can receive those and know when the broker is disconnected and subsequently reconnects. So this should give you all the facilities needed to deal with the situation.

To be sure if the exceptions were not to be raised, you would probably log a ticket that messages appear to be sent but are not. That in my mind would be a bigger issue.

[spring-projects-issues]

Rossen Stoyanchev commented

See commit 86785f.