[Bug] [Skywalking-java] wrong tid and spans for httpasyncclient-4.x-plugin

[tvvis]

Search before asking

• I had searched in the issues and found no similar issues.

Apache SkyWalking Component

Java Agent (apache/skywalking-java)

What happened

I am sure it should only contains one http request (the first one) in this segment.
I check the httpasyncclient-4.x-plugin. I think it just get the skywalking context capture from http connection and start the span when I/O dispatcher ready to start the request. Keep the skywalking context thread local and end it when consume response.
But before the previous request has finished, some other requests could reuse this same I/O dispatcher and create their span in wrong context. I guess this is the reason why they have wrong tid and this segment has some unexpected spans.

What you expected to happen

Request have right trace id.

How to reproduce

Errors can occur with high concurrency. For us, it's about 200 QPS and 10 IO thread count. Set IO thread count to 1 could make it easier to reproduce it.

Anything else

The skywalking-java version is 9.0.0.

Are you willing to submit a pull request to fix on your own?

• Yes I am willing to submit a pull request on my own!

Code of Conduct

• I agree to follow this project's Code of Conduct

[wu-sheng]

SkyWalking community usually only hosts plugins, as maintainers can't keep eyes on so many ones.

If you want to fix and can explain what caused this, we could help. Otherwise, we have to wait for any volunteer further.

[wu-sheng]

But before the previous request has finished, some other requests could reuse this same I/O dispatcher and create their span in wrong context. I guess this is the reason why they have wrong tid and this segment has some unexpected spans.

If something reuses the dispatch thread, maybe we need to follow the context switch and make sure context changed accordingly.