【RocketMQ源码】三、Producer 源码学习

谁借莪１个温暖的怀抱￠ 2023-02-26 10:24 21阅读 0赞

# 一、启动流程 #

## 1.1 默认启动类解析 ##

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查看这个start 的引用可以发现它是基于 DefaultMQProducer 这个类创建的，即需要通过这个类创建 Producer 并发送消息

![20200715111353959.png][]

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同时可以看到这个类中定义了各种消息的发送方法和默认参数

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM0NDE2MzMx_size_16_color_FFFFFF_t_70 3][]

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## 1.2 默认参数解析 ##

<table> 
 <tbody> 
  <tr> 
   <td><strong>参数名称</strong></td> 
   <td style="width:516px;"><strong>参数作用</strong></td> 
  </tr> 
  <tr> 
   <td>producerGroup</td> 
   <td style="width:516px;">生产者所属组</td> 
  </tr> 
  <tr> 
   <td>createTopicKey</td> 
   <td style="width:516px;">默认Topic</td> 
  </tr> 
  <tr> 
   <td>defaultTopicQueueNums</td> 
   <td style="width:516px;">默认主题在每一个Broker队列数量</td> 
  </tr> 
  <tr> 
   <td>sendMsgTimeout</td> 
   <td style="width:516px;">发送消息默认超时时间，默认3s</td> 
  </tr> 
  <tr> 
   <td>compressMsgBodyOverHowmuch</td> 
   <td style="width:516px;">消息体超过该值则启用压缩，默认4k</td> 
  </tr> 
  <tr> 
   <td>retryTimesWhenSendFailed</td> 
   <td style="width:516px;">同步方式发送消息重试次数，默认为2，总共执行3次</td> 
  </tr> 
  <tr> 
   <td>retryTimesWhenSendAsyncFailed</td> 
   <td style="width:516px;">异步方法发送消息重试次数，默认为2</td> 
  </tr> 
  <tr> 
   <td>retryAnotherBrokerWhenNotStoreOK</td> 
   <td style="width:516px;">消息重试时选择另外一个Broker时，是否不等待存储结果就返回，默认为false</td> 
  </tr> 
  <tr> 
   <td>maxMessageSize</td> 
   <td style="width:516px;">允许发送的最大消息长度，默认为4M</td> 
  </tr> 
 </tbody> 
</table>

## 1.3 代码跟踪 ##

*代码：DefaultMQProducerImpl\#start*

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM0NDE2MzMx_size_16_color_FFFFFF_t_70 5][]

点开 MQClientManager，可以看到整个JVM中只有一个 MQClientManager 实例，维护一个MQClientInstance缓存表

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查看MQClientInstance，发现其封装了RocketMQ网络处理API，是消息生产者和消息消费者与NameServer、Broker打交道的网络通道

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM0NDE2MzMx_size_16_color_FFFFFF_t_70 8][]

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# 二、消息发送 #

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[20200715111353959.png]: /images/20230209/fb95aba35b2d46f99a5c03892fa7927f.png
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