redis之发布与订阅(publish/subscribe模式)

ゝ一世哀愁。 2021-09-14 19:46 360阅读 0赞

[http://blog.csdn.net/u011499747/article/details/51232981][http_blog.csdn.net_u011499747_article_details_51232981]

发布与订阅（publish/subscribe）模式，简称为pub/sub模式，redis也实现了这种模式。

# redis提供的发布订阅命令 #

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   <th style="font-size:14px; color:rgb(79,79,79); line-height:22px; border:1px solid rgb(221,221,221); padding:8px; text-align:left; word-wrap:break-word; word-break:normal; vertical-align:middle; background-color:rgb(239,243,245)"> 用例和描述</th> 
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   <td style="font-size:14px; color:rgb(79,79,79); line-height:22px; border:1px solid rgb(221,221,221); padding:8px; text-align:left; word-wrap:break-word; word-break:normal; vertical-align:middle"> subscribe</td> 
   <td style="font-size:14px; color:rgb(79,79,79); line-height:22px; border:1px solid rgb(221,221,221); padding:8px; text-align:left; word-wrap:break-word; word-break:normal; vertical-align:middle"> subscribe channel [channel …] 订阅一个或多个频道</td> 
  </tr> 
  <tr style="border-width:1px 0px 0px; border-right-style:initial; border-bottom-style:initial; border-left-style:initial; border-right-color:initial; border-bottom-color:initial; border-left-color:initial; border-top-style:solid; border-top-color:rgb(221,221,221); background-color:rgb(247,247,247)"> 
   <td style="font-size:14px; color:rgb(79,79,79); line-height:22px; border:1px solid rgb(221,221,221); padding:8px; text-align:left; word-wrap:break-word; word-break:normal; vertical-align:middle"> unsubscribe</td> 
   <td style="font-size:14px; color:rgb(79,79,79); line-height:22px; border:1px solid rgb(221,221,221); padding:8px; text-align:left; word-wrap:break-word; word-break:normal; vertical-align:middle"> unsubscribe [channel [channel …]] 退订频道，如果没有指定频道，则退订所有的频道</td> 
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  <tr style="border-width:1px 0px 0px; border-right-style:initial; border-bottom-style:initial; border-left-style:initial; border-right-color:initial; border-bottom-color:initial; border-left-color:initial; border-top-style:solid; border-top-color:rgb(221,221,221)"> 
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   <td style="font-size:14px; color:rgb(79,79,79); line-height:22px; border:1px solid rgb(221,221,221); padding:8px; text-align:left; word-wrap:break-word; word-break:normal; vertical-align:middle"> publish channel message 给指定的频道发消息</td> 
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  <tr style="border-width:1px 0px 0px; border-right-style:initial; border-bottom-style:initial; border-left-style:initial; border-right-color:initial; border-bottom-color:initial; border-left-color:initial; border-top-style:solid; border-top-color:rgb(221,221,221); background-color:rgb(247,247,247)"> 
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   <td style="font-size:14px; color:rgb(79,79,79); line-height:22px; border:1px solid rgb(221,221,221); padding:8px; text-align:left; word-wrap:break-word; word-break:normal; vertical-align:middle"> psubscribe pattern [pattern …] 订阅给定模式相匹配的所有频道</td> 
  </tr> 
  <tr style="border-width:1px 0px 0px; border-right-style:initial; border-bottom-style:initial; border-left-style:initial; border-right-color:initial; border-bottom-color:initial; border-left-color:initial; border-top-style:solid; border-top-color:rgb(221,221,221)"> 
   <td style="font-size:14px; color:rgb(79,79,79); line-height:22px; border:1px solid rgb(221,221,221); padding:8px; text-align:left; word-wrap:break-word; word-break:normal; vertical-align:middle"> punsubscribe</td> 
   <td style="font-size:14px; color:rgb(79,79,79); line-height:22px; border:1px solid rgb(221,221,221); padding:8px; text-align:left; word-wrap:break-word; word-break:normal; vertical-align:middle"> punsubscribe [pattern [pattern …]] 退订给定的模式，如果没有指定模式，则退订所有模式</td> 
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## 实例 ##

一个客户端订阅test-channel   
![一个客户端订阅test-channel][test-channel]  
一个客户端向test-channel发消息   
![一个客户端向test-channel发消息][test-channel 1]

# 缺点 #

所有pub/sub很有用，但是redis的实现有这么几个问题：   
1，如果一个客户端订阅了频道，但自己读取消息的速度却不够快的话，那么不断积压的消息会使redis输出缓冲区的体积变得越来越大，这可能使得redis本身的速度变慢，甚至直接崩溃。   
2，这和数据传输可靠性有关，如果在订阅方断线，那么他将会丢失所有在短线期间发布者发布的消息，这个让绝不多数人都很失望吧。

[http_blog.csdn.net_u011499747_article_details_51232981]: http://blog.csdn.net/u011499747/article/details/51232981
[test-channel]: /images/20210527/12b209706c0b4e8bb4a2f005e3eb7c45.png
[test-channel 1]: /images/20210527/9003a4456ba244d1ac684219cc296878.png