[GitHub] [rocketmq] MountainOne commented on issue #1588: Retry doesn't work when sending msg in aync mode(eg. when broker is down)

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MountainOne commented on issue #1588: Retry doesn't work when sending msg in aync mode(eg. when broker is down)
URL: https://github.com/apache/rocketmq/issues/1588#issuecomment-554638653
 
 
   Message retry resynchronization in RocketMQ is implemented by calling the `sendKeynelImpl()` method in a for loop in `DefaultMQProducerImpl#sendDefaultImpl()`. The number of retries is obtained by `DefaultMQProducer#getRetryTimesWhenSendFailed()`.
   Asynchronous message sending retry is implemented by `MQClientAPIImpl#onExceptionImpl()` recursively calling `MQClientAPIImpl#sendMessageAsync()` method in case of exception. The number of retries is obtained by `DefaultMQProducerImpl#.getRetryTimesWhenSendAsyncFailed()`. The default value is 2.
   Therefore, if you do not set the number of asynchronous retries, you will retry at least 2 times, and the message will not be sent because there is no retry. Only the location of the asynchronous and synchronous send retry implementations is different, resulting in such a judgment.
   
   在 RocketMQ 中同步的消息发送重试是通过`DefaultMQProducerImpl#sendDefaultImpl()`中的 for 循环，循环调用`sendKeynelImpl()`方法实现的。重试次数由`DefaultMQProducer#getRetryTimesWhenSendFailed()`获得。
   而异步的消息发送重试是在出现异常的情况下，由`MQClientAPIImpl#onExceptionImpl()`递归调用`MQClientAPIImpl#sendMessageAsync()`方法实现的。重试次数由`DefaultMQProducerImpl#.getRetryTimesWhenSendAsyncFailed()`获得，缺省值为 2。
   所以在不设置异步重试次数的情况下，也会至少重试 2 次，不会因为没有重试而导致消息发送失败。只是异步和同步发送重试实现的位置不一样，导致产生了这样判断。

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