How do I call an async function in a new process using multiprocessing?

Question

I created a server that wait for webhook signal, and when there is signal, it will create a new process to run the loop() function, and when running the loop() function, I want it to call the function printmessage() asynchronously, so it will run the next line in the loop function without waiting the printmessage() function finish processing, but I got the following errors, how I resolve it?

#main.py
import time
from fastapi import Request, FastAPI
import multiprocessing as mp
import uvicorn
import asyncio


async def printmessage(fruit):
    print(fruit)
    time.sleep(5) 
    
async def loop(fruit):
    while True:     
        task = asyncio.create_task(printmessage(fruit))          
        time.sleep(1)

fruit="apple"
if __name__ == '__main__':

    print("PROGRAM LAUNCH...")
    print("WEBHOOK RECEIVE READY...")   

 
app = FastAPI()    
@app.post("/webhook")
async def webhook(request : Request):       

    print("WEBHOOK RECEIVED")    
    p = mp.Process(target=loop,args=[fruit])
    p.start() 
    print('done')   
    return 'WEBHOOK RECEIVED' 

The intended output should be printing apple every 1 second.

ERRORS:

RuntimeWarning: coroutine 'loop' was never awaited
  self._target(*self._args, **self._kwargs)
RuntimeWarning: Enable tracemalloc to get the object allocation traceback

I tried the following way to avoid the errors but there is no output at all:

#main.py
import time
from fastapi import Request, FastAPI
import multiprocessing as mp
import uvicorn
import asyncio


async def printmessage(fruit):
    print(fruit)
    time.sleep(5) 
    
async def loop(fruit):
    while True:     
        task = asyncio.create_task(printmessage(fruit))          
        time.sleep(1)

def preloop(fruit):
    asyncio.run(loop(fruit))

fruit="apple"
if __name__ == '__main__':

    print("PROGRAM LAUNCH...")
    print("WEBHOOK RECEIVE READY...")  

 
app = FastAPI()    
@app.post("/webhook")
async def webhook(request : Request):       

    print("WEBHOOK RECEIVED")    
    p = mp.Process(target=preloop,args=[fruit])
    p.start() 
    print('done')   
    return 'WEBHOOK RECEIVED' 

Answer 1

Here is how you can call an async function in a new process using multiprocessing. In this code, each request to /webhook creates a new process, which prints apple every 5 seconds.

from __future__ import annotations
import asyncio
from multiprocessing import Process
from fastapi import FastAPI

app = FastAPI()

process_pool: list[Process] = []


async def print_message(fruit):
    print(fruit)


async def loop(fruit):
    while True:
        await print_message(fruit)
        await asyncio.sleep(5)


def run_loop(fruit):
    asyncio.run(loop(fruit))


@app.get("/webhook")
async def webhook():
    print("WEBHOOK RECEIVED")
    fruit = "apple"
    process = Process(target=run_loop, args=(fruit,))
    process_pool.append(process)
    process.start()
    print('done')
    return 'WEBHOOK RECEIVED'


@app.on_event("shutdown")
async def shutdown_event():
    for process in process_pool:
        process.kill()
    for process in process_pool:
        while process.is_alive():
            continue
        process.close()


if __name__ == '__main__':
    print("PROGRAM LAUNCH...")
    print("WEBHOOK RECEIVE READY...")