Message retry

Retries for ordered messages

If a consumer fails to consume an ordered message, Message Queue for Apache RocketMQ automatically retries sending the message continuously at an interval of one second. This may block message consumption. Therefore, when you use ordered messages, ensure that your application can monitor and handle consumption failures promptly to prevent blocking.

Retries for unordered messages

Unordered messages include normal, scheduled, delayed, and transactional messages. You can set a response code to trigger message retry if a consumer fails to consume such messages.

Unordered message retry takes effect only in clustering consumption. If message consumption fails in broadcasting mode, consumers do not attempt to consume failed messages a second time. Instead, they continue consuming new messages.

Number of retries

Message Queue for Apache RocketMQ allows a maximum of 16 retries for each message by default. The following table lists the intervals for the retries.

If a message fails after 16 retries, it will not be delivered. Strictly based on the preceding intervals, if the consumption of a message continuously fails, the message is retried 16 times within 4 hours and 46 minutes. After this time, the message will not be delivered.

Configuration method

• Configure retries after a message consumption failure

  In clustering consumption, a message retry is expected after a message consumption failure. This must be configured in the MessageListener operation in one of the following methods:

  • Method 1: Return Action.ReconsumeLater (recommended).
  • Method 2: Return null.
  • Method 3: Throw an exception.

  Sample code

  public class MessageListenerImpl implements MessageListener {
  
      @Override
      public Action consume(Message message, ConsumeContext context) {
          // The message processing logic throws an exception. The message will be retried.
          doConsumeMessage(message);
          // Method 1: Return Action.ReconsumeLater and retry the message.
          return Action.ReconsumeLater;
          // Method 2: Return null and retry the message.
          return null;
          // Method 3: Throw an exception and retry the message.
          throw new RuntimeException("Consumer Message exception");
      }
  }

• Disable retries after a message consumption failure

  In clustering consumption, no message retry is expected after a message consumption failure. Exceptions thrown by the consumption logic must be caught, and Action.CommitMessage is returned. After that, the message will not be retried.

  Sample code

  public class MessageListenerImpl implements MessageListener {
  
      @Override
      public Action consume(Message message, ConsumeContext context) {
          try {
              doConsumeMessage(message);
          } catch (Throwable e) {
              // Catch all exceptions in the consumption logic and return Action.CommitMessage.
              return Action.CommitMessage;
          }
          // If message consumption does not fail, return Action.CommitMessage.
          return Action.CommitMessage;
      }
  }

• Customize the maximum number of retries
  Note To customize the log configuration of your Message Queue for Apache RocketMQ client, you must upgrade the TCP Java SDK to version 1.2.2 or later.

  Message Queue for Apache RocketMQ allows you to set the maximum number of retries when the consumer is started. The following describes how custom retry intervals are determined:

  • If the maximum number of retries is less than or equal to 16, the retry interval is as described in the preceding table.
  • If the maximum number of retries is greater than 16, the interval of the 17th and later retries is 2 hours.

  You can use the following the configuration method:

  Properties properties = new Properties();
  // Set the maximum number of message retries for the group ID to 20. The value is of the string type.
  properties.put(PropertyKeyConst.MaxReconsumeTimes,"20");
  Consumer consumer =ONSFactory.createConsumer(properties);

  Notice

  • The configuration of the maximum number of message retries applies to all consumer instances with the same group ID.
  • If MaxReconsumeTimes is set for only one of the two consumer instances with the same group ID, the configuration applies to both consumer instances.
  • The configuration of the last started consumer instance overwrites the configurations of previously started instances.

Retrieve the number of retries

After a consumer receives a message, the consumer can retrieve the number of retries in the following method:

public class MessageListenerImpl implements MessageListener {

    @Override
    public Action consume(Message message, ConsumeContext context) {
        // Retrieve the number of retries.
        System.out.println(message.getReconsumeTimes());
        return Action.CommitMessage;
    }
}