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Posted to commits@servicecomb.apache.org by GitBox <gi...@apache.org> on 2022/06/10 03:10:33 UTC
[GitHub] [servicecomb-java-chassis] hailin84 opened a new issue, #3051: 是否有计划支持类似于async servlet这种机制
hailin84 opened a new issue, #3051:
URL: https://github.com/apache/servicecomb-java-chassis/issues/3051
场景：
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页面展示二维码，一个long polling请求检查服务端扫码结果，这个请求在服务端不会立即返回，而是标注成async，然后进入异步线程池执行任务，Http处理线程见到这个请求是异步的，就知道先不将响应写回客户端，也不做flushbuffer、释放资源之类的操作（即客户端暂时不会收到响应），然后就完成了处理，释放Http处理线程。服务端异步任务执行完毕（超时或者成功处理），重新进入Http请求处理流程，这时候通过异步相关的标志得知，这个请求不再需要走前面的处理逻辑，而是只需要把响应写回即可。
如果服务端返回超时，那么客户端立即开始下一次long polling请求。long polling的好处就是一旦扫完码，页面客户端马上就能感知到结果。比普通的页面客户端轮询效果更好。
跟reactive还是有区别的。async servlet不占用Http处理线程，但是会占用TCP连接，因为必须没响应客户端，所以连接不会关闭。相对来说，能支持的TCP连接数是远大于线程数的，所以async servlet可以做到比较高的吞吐量。
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[GitHub] [servicecomb-java-chassis] hailin84 commented on issue #3051: 是否有计划支持类似于async servlet这种机制
Posted by GitBox <gi...@apache.org>.
hailin84 commented on issue #3051:
URL: https://github.com/apache/servicecomb-java-chassis/issues/3051#issuecomment-1152061129
我们没有用Servlet，用的是Rest Over Vert.x。想要达到类似的效果。
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[GitHub] [servicecomb-java-chassis] hailin84 commented on issue #3051: 是否有计划支持类似于async servlet这种机制
Posted by GitBox <gi...@apache.org>.
hailin84 commented on issue #3051:
URL: https://github.com/apache/servicecomb-java-chassis/issues/3051#issuecomment-1152090641
所有的文档我都反反复复翻了几遍了。你对比一下Tomcat的实现，就知道over Vert.x是压根不支持了。代码里也没有预留扩展点。这有个Tomcat的源码分析：
https://www.helloworld.net/p/6353081200
over servlet应该是天然就支持的，毕竟Tomcat有实现。你们不打算支持就算了吧，我们只能想想其他办法了。
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[GitHub] [servicecomb-java-chassis] liubao68 commented on issue #3051: 是否有计划支持类似于async servlet这种机制
Posted by GitBox <gi...@apache.org>.
liubao68 commented on issue #3051:
URL: https://github.com/apache/servicecomb-java-chassis/issues/3051#issuecomment-1152051526
我觉得我的理解是对的，但不是很清楚你的疑问点在哪里。 建议可以试试 servlet 模式跑一下 java chassis， 可以帮助理解。
参考 [embededed servlet](https://servicecomb.apache.org/references/java-chassis/zh_CN/using-java-chassis-in-spring-boot/introduction.html) 或者 [standalone tomcat](https://servicecomb.apache.org/references/java-chassis/zh_CN/transports/rest-over-servlet.html) . [samples](https://github.com/apache/servicecomb-samples) 有对应的例子。
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[GitHub] [servicecomb-java-chassis] hailin84 commented on issue #3051: 是否有计划支持类似于async servlet这种机制
Posted by GitBox <gi...@apache.org>.
hailin84 commented on issue #3051:
URL: https://github.com/apache/servicecomb-java-chassis/issues/3051#issuecomment-1151910031
@liubao68 你说的跟我说的不是一回事。你指的异步是说servlet不在event-loop里执行而是在另一个单独的线程池执行吧？但是不管在哪里执行，执行完就立马响应客户端了。我说的这个场景线程可以执行完毕，但是不响应客户端。而是等到后面异步工作做完，再响应客户端。换句话说是需要将处理请求的流程分成两段，第一段是执行Controller、Filter等业务逻辑，第二段是根据把Response写回给客户端。第二段需要检查一下是否是异步，如果是，则先不写回。整个处理流程需要提供重入机制。我看代码主要是在AbstractRestInvocation里，并没有看到相应的机制。
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[GitHub] [servicecomb-java-chassis] liubao68 commented on issue #3051: 是否有计划支持类似于async servlet这种机制
Posted by GitBox <gi...@apache.org>.
liubao68 commented on issue #3051:
URL: https://github.com/apache/servicecomb-java-chassis/issues/3051#issuecomment-1152095916
可以再看看 [异步处理的使用](https://servicecomb.apache.org/references/java-chassis/zh_CN/build-provider/reactive.html)
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[GitHub] [servicecomb-java-chassis] liubao68 commented on issue #3051: 是否有计划支持类似于async servlet这种机制
Posted by GitBox <gi...@apache.org>.
liubao68 commented on issue #3051:
URL: https://github.com/apache/servicecomb-java-chassis/issues/3051#issuecomment-1151895858
java chassis的所有请求处理都是这种模式的。工作于servlet模式下，使用的是async servlet。 工作于vert.x模式下，也类似这种模式。
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[GitHub] [servicecomb-java-chassis] hailin84 closed issue #3051: 是否有计划支持类似于async servlet这种机制
Posted by GitBox <gi...@apache.org>.
hailin84 closed issue #3051: 是否有计划支持类似于async servlet这种机制
URL: https://github.com/apache/servicecomb-java-chassis/issues/3051
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[GitHub] [servicecomb-java-chassis] liubao68 commented on issue #3051: 是否有计划支持类似于async servlet这种机制
Posted by GitBox <gi...@apache.org>.
liubao68 commented on issue #3051:
URL: https://github.com/apache/servicecomb-java-chassis/issues/3051#issuecomment-1152070188
Rest Over Vert.x类似的， 感觉你只是对event-loop线程池和业务线程池的理解有误解。
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