[undertow-dev] Supporting Flight Recorder events

[Philippe Marschall]

Hello

With Java 11 Flight Recorder is now part of OpenJDK 11 [1], Open Source 
and free to use. I hacked something together how Undertow could 
integrate with this [2]. This can become quite powerful as you can track 
down what events happened during processing of that HTTP exchange. It 
becomes even more powerful once other components (database, caching) 
also generate events and you can correlate them.

I wanted to ask whether it makes any sense to upstream this? Obviously 
it will always have to be optional as it only works with OpenJDK 11+ and 
there is a small runtime overhead.

I have to say that I am not super familiar with the Flight Recorder API. 
For example I am not sure when an event is started in one thread but 
completed in an other thread whether that needs to be handled specially. 
I am not sure whether this could happen for async servlet.
Also I am not sure whether the ExchangeCompleteListener is called if 
handleRequest on the next HttpHandler throws an exception.


  [1] https://openjdk.java.net/jeps/328
  [2] https://github.com/marschall/undertow-jfr

Cheers
Philippe