Coroutine-aware wall-time profiling

For the sake of profiling ASGI apps, it would be really helpful if there was a way to make use of python 3.7’s contextvars while filtering via yappi.get_func_stats. If yappi supported this, you could get per-request-response-cycle profiling through an ASGI middleware.

I’m not sure if the necessary functionality already exists or not, but wanted to open an issue in case anyone else has thought about this, or in case someone is aware of an existing way to accomplish this.

See https://github.com/tiangolo/fastapi/issues/701 for more context on how we’d like to use this.

[sumerc]

Hi @dmontagu, I have been able to run your test case successfully! (I have renamed the test file to be test_asyncio_context_vars.py and added it to the coroutine-profiling branch.). A new API has been written and first tests indicate it is stable. I am extensively writing test cases, it would be nice if you can also get a look at it. The only change I needed to do is to change set_context_id_callback to the new API: set_tag_callback. So, with the new version of Yappi you can simply tag any function regardless of thread or coroutine. I hope you can start using it in FastAPI and tell me about the progress.

[sumerc]

Ok. This will hopefully be my final update: I have done few changes related to get_func_stats() again: implemented filtering on C side and moved same tags into same hashtables. With these improvements, now 1000 concurrent requests is being done in ~3.7 secs! which seems to indicate 10x improvement. I think we no more need filtering on clear_stats() as the number of tags does not affect performance anymore while filtering on tag.(as we use a hashtable underneath.)

Anyway, I will be finalizing the tests and hopefully will be releasing a new version which includes lots of new, exciting stuff. Looking forward to your latest feedback and use cases in FastAPI, too, of course.