failing to capture FastAPI uvicorn threads, only seeing the _MainThread

[MorAlterya]

failing to capture FastAPI uvicorn threads, only seeing the _MainThread

[davidvoler]

from fastapi import FastAPI
from uvicorn import Config, Server

import yappi
import sys
import asyncio
import random
from logging import getLogger

logger = getLogger(__name__)
current_module = sys.modules[__name__]
yappi.set_clock_type("WALL") 

app = FastAPI()




async def handle_messages():
    r = random.random()
    # r = 3
    await asyncio.sleep(r)
    logger.error(f"waited for {r} seconds")
    


async def listener():
    logger.error("listener started")
    while True:
        asyncio.create_task(handle_messages())
        await asyncio.sleep(1)


@app.on_event("startup")
async def startup():
    asyncio.create_task(listener())

@app.get("/")
async def root():
    return {"message": "Hello World"}


@app.get("/stats")
async def stats():
    stats = yappi.get_func_stats(
        filter_callback=lambda x: yappi.module_matches(x, [current_module])
    )
    stats.sort("totaltime", "desc").print_all()
    stats.strip_dirs()
    stats.print_all()
    yappi.clear_stats()
    ret = []
    for s in stats:
        ret.append((s[15],s[3], s[14], s[6]))
    return ret


if __name__ == "__main__":
    with yappi.run():
        config = Config(app)
        server = Server(config)
        server.run()

Save the the above code as main.py
The follwing code is working when running :
python main.py

But it will not work if you run:
uvicorn main:app
This make sense as when you run with uvicorn you skip the if name == "main": part

I am happy with this workaround.
Will it work for you @MorAlterya ?

[kwuite]

@MorAlterya

Have you tried returning results first and then executing yappi.stop()?

yappi.start()  # 'profile_threads=True' default value

uvicorn.run("main:app")

yappi.get_func_stats().print_all()
yappi.get_threads_stats().print_all()
yappi.stop()

[sumerc]

@kwuite , it should not make any difference if the profiler is stopped or not.

@MorAlterya , could you please provide an example application that reproduces the problem. In theory, the code you have provided should just work fine, and we have many unit tests confirming it should work. I need to understand what is different in your case. What version of FastAPI, how you run it..etc. A simple example demonstrating this error would be very useful.

[MorAlterya]

The exact configuration I provided produces results for the main thread only, tested it but calling endpoints and not even seeing the output.

FastAPI version: 0.88.0
yappi version: 1.4.0

Our project no longer runs on FastAPI, we moved to a task-based system, and now Yappi works great!
We have excellent profiling from threads. Now none of them are created by uvicorn/FastAPI.