Callbacks and Events

Rqueue provides various types of callbacks and events for handling message processing and application events.

Message Processors/Callbacks

Rqueue supports the following message processors, which can be used for different purposes such as setting up tracers or managing transactions.

Pre Execution Processor

This message processor is invoked before calling the handler methods. If the processor returns false, the message handler will not be called.

class RqueueConfiguration {

  private MessageProcessor preExecutorMessageProcessor() {
    // return message processor object
  }

  @Bean
  public SimpleRqueueListenerContainerFactory simpleRqueueListenerContainerFactory() {
    SimpleRqueueListenerContainerFactory factory = new SimpleRqueueListenerContainerFactory();
    MessageProcessor preExecutorMessageProcessor = preExecutorMessageProcessor();
    factory.setPreExecutionMessageProcessor(preExecutorMessageProcessor);
    return factory;
  }
}

Discard Execution Processor

This message processor is called whenever a message is discarded due to exceeding the retry limit.

class RqueueConfiguration {

  private MessageProcessor discardMessageProcessor() {
    // return message processor object
  }

  @Bean
  public SimpleRqueueListenerContainerFactory simpleRqueueListenerContainerFactory() {
    SimpleRqueueListenerContainerFactory factory = new SimpleRqueueListenerContainerFactory();
    MessageProcessor discardMessageProcessor = discardMessageProcessor();
    factory.setDiscardMessageProcessor(discardMessageProcessor);
    return factory;
  }
}

Dead Letter Queue Processor

This message processor is called whenever a message is moved to the dead letter queue.

class RqueueConfiguration {

  private MessageProcessor deadLetterQueueMessageProcessor() {
    // return message processor object
  }

  @Bean
  public SimpleRqueueListenerContainerFactory simpleRqueueListenerContainerFactory() {
    SimpleRqueueListenerContainerFactory factory = new SimpleRqueueListenerContainerFactory();
    MessageProcessor deadLetterQueueMessageProcessor = deadLetterQueueMessageProcessor();
    factory.setDeadLetterQueueMessageProcessor(deadLetterQueueMessageProcessor);
    return factory;
  }
}

Manual Deletion Processor

This message processor is called whenever a message is deleted manually.

class RqueueConfiguration {

  private MessageProcessor manualDeletionMessageProcessor() {
    // return message processor object
  }

  @Bean
  public SimpleRqueueListenerContainerFactory simpleRqueueListenerContainerFactory() {
    SimpleRqueueListenerContainerFactory factory = new SimpleRqueueListenerContainerFactory();
    MessageProcessor manualDeletionMessageProcessor = manualDeletionMessageProcessor();
    factory.setManualDeletionMessageProcessor(manualDeletionMessageProcessor);
    return factory;
  }
}

Post Execution Processor

This message processor is called upon successful consumption of the message.

class RqueueConfiguration {

  private MessageProcessor postExecutionMessageProcessor() {
    // return message processor object
  }

  @Bean
  public SimpleRqueueListenerContainerFactory simpleRqueueListenerContainerFactory() {
    SimpleRqueueListenerContainerFactory factory = new SimpleRqueueListenerContainerFactory();
    MessageProcessor postExecutionMessageProcessor = postExecutionMessageProcessor();
    factory.setPostExecutionMessageProcessor(postExecutionMessageProcessor);
    return factory;
  }
}

Events

Rqueue generates two types of application events: one for Rqueue container start/shutdown and another for task execution status.

Job/Task Execution Event

Upon completion of each task, Rqueue generates RqueueExecutionEvent, which the application can listen to. This event contains a job object providing all relevant information about the job.

Application Bootstrap Event

Once the RqueueListenerContainer is started, it emits RqueueBootstrapEvent. This event is generated post container shutdown and can be used for tasks such as queue registration or cleaning up local states.