Skywalking: The webflux-plugin is not working properly

[cyejing]

Please answer these questions before submitting your issue.

• Why do you submit this issue?
• [ ] Question or discussion
• [X] Bug
• [ ] Requirement
• [ ] Feature or performance improvement

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Question

• What do you want to know?
  The webflux-plugin is not working properly
  because WebFlux is Reactive Programming ，plugin use ThreadLocal is not working properly

webflux-plugin 并不能正常工作,因为 WebFlux 是响应式编程。 处理的线程会发生变化，插件内部使用ThreadLocal 根本不能获取到原来线程的信息，还会因为未能正确关闭span信息 导致ThreadLocal一直没有释放

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Bug

• What happen?
  this is debug msg：
  
  
  
  webflux-plugins Intercept 3 method ，the thread has changed when the method is executed

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Requirement or improvement

• Need to deal with it without relying on ThreadLocal

[wu-sheng]

@cyejing You could check the test at https://github.com/apache/skywalking/tree/master/test/plugin/scenarios/webflux-scenario, and get the idea what is the difference.

@zhaoyuguang Maybe we just support part of it. I remember we just support webflux + Spring MVC, rather than real Reactive framework. You know better than me.

[zhaoyuguang]

Indeed, as @cyejing said, The webflux plugin doesn't perform well after using reactive improvements, I am thinking about whether there is a better solution, such as webflux agent implementation similar to webflux interceptor, Can add a help wanted tag to see if there is any webflux expert to give some advising?

[cyejing]

I have a idea, can use Mono doFinally method , and put TraceContext into SkyWalkingDynamicField of ServerWebExchange . collect the span when the Mono ends.
I have implemented it in a test environment and it works fine.
I can submit new PR to fix

[cyejing]

I have a problem. method of Mono doFinally parameter is Consumer , this is java8 api java.util.function.Consumer . but agent pom set <compiler.version>1.6</compiler.version> .
Is there any good way?

[wu-sheng]

You could add an optional plugin, which could use the jdk8 compile level.