This document mainly introduces the message retry mechanisms and their usage in TDMQ for RocketMQ.
Feature Introduction
When a message is consumed by a consumer for the first time but does not receive a normal acknowledgment, or when the user explicitly requests the server to redeliver the message, TDMQ for RocketMQ will automatically redeliver the message through the consumption retry mechanism until the message is successfully consumed. If the message still fails to be consumed after a certain number of retries, the retry process stops, and the message is delivered to a dead letter queue.
When messages enter the dead letter queue, it indicates that TDMQ for RocketMQ no longer automatically processes the messages. At this point, manual intervention is generally required to handle these messages. You can write a dedicated client to subscribe to the dead letter topic to process such messages.
Note:
The broker automatically retries only in the clustering consumption mode. No retry occurs in the broadcasting consumption mode.
The following three scenarios are treated as consumption failures and will trigger a retry:
The consumer returns ConsumeResult.FAILURE.
The consumer returns null.
The consumer explicitly or implicitly throws an exception.
Number of Retries
When a message needs to be retried, TDMQ for RocketMQ uses the configured messageDelayLevel parameter to define the number of retries and retry intervals.
messageDelayLevel=1s 5s 10s 30s 1m 2m 3m 4m 5m 6m 7m 8m 9m 10m 20m 30m 1h 2h
Since the first delayLevel in the SDK starts at 3, the relationship between the number of retries and retry intervals is as follows:
|
1 | 10 seconds | 9 | 7 minutes |
2 | 30 seconds | 10 | 8 minutes |
3 | 1 minute | 11 | 9 minutes |
4 | 2 minutes | 12 | 10 minutes |
5 | 3 minutes | 13 | 20 minutes |
6 | 4 minutes | 14 | 30 minutes |
7 | 5 minutes | 15 | 1 hour |
8 | 6 minutes | 16 | 2 hours |
Usage Methods
No special handling is required. The 5.0 SDK follows the rules described above.
If you need to adjust the number of retries, you can set the following parameters for the consumer.
pushConsumer.setMaxReconsumeTimes(3);