This snippet of code (a minimal server running in a thread, code taken from here) works fine with Python3.8.3 but raises an error message with Python3.9.0:
import asyncio
import threading
from aiohttp import web
def aiohttp_server():
def say_hello(request):
return web.Response(text='Hello, world')
app = web.Application()
app.add_routes([web.get('/', say_hello)])
runner = web.AppRunner(app)
return runner
def run_server(runner):
loop = asyncio.new_event_loop()
asyncio.set_event_loop(loop)
loop.run_until_complete(runner.setup())
site = web.TCPSite(runner, 'localhost', 8080)
loop.run_until_complete(site.start())
loop.run_forever()
t = threading.Thread(target=run_server, args=(aiohttp_server(),))
t.start()
The error message:
Exception in thread Thread-1:
Traceback (most recent call last):
File "/usr/lib/python3.9/threading.py", line 954, in _bootstrap_inner
self.run()
File "/usr/lib/python3.9/threading.py", line 892, in run
self._target(*self._args, **self._kwargs)
File "/home/alkhinoos/nikw/nikw/z2.py", line 21, in run_server
loop.run_until_complete(site.start())
File "/usr/lib/python3.9/asyncio/base_events.py", line 642, in run_until_complete
return future.result()
File "/usr/lib/python3.9/site-packages/aiohttp/web_runner.py", line 121, in start
self._server = await loop.create_server(
File "/usr/lib/python3.9/asyncio/base_events.py", line 1460, in create_server
infos = await tasks.gather(*fs, loop=self)
File "/usr/lib/python3.9/asyncio/base_events.py", line 1400, in _create_server_getaddrinfo
infos = await self._ensure_resolved((host, port), family=family,
File "/usr/lib/python3.9/asyncio/base_events.py", line 1396, in _ensure_resolved
return await loop.getaddrinfo(host, port, family=family, type=type,
File "/usr/lib/python3.9/asyncio/base_events.py", line 856, in getaddrinfo
return await self.run_in_executor(
File "/usr/lib/python3.9/asyncio/base_events.py", line 809, in run_in_executor
executor = concurrent.futures.ThreadPoolExecutor(
File "/usr/lib/python3.9/concurrent/futures/__init__.py", line 49, in __getattr__
from .thread import ThreadPoolExecutor as te
File "/usr/lib/python3.9/concurrent/futures/thread.py", line 37, in <module>
threading._register_atexit(_python_exit)
File "/usr/lib/python3.9/threading.py", line 1374, in _register_atexit
raise RuntimeError("can't register atexit after shutdown")
RuntimeError: can't register atexit after shutdown
What's going on ? The same problem appears with Python 3.9.1. Is this problem solved with Python 3.9.2 ? Maybe a relative issue here.
As mentioned in Python manual - Thread Objects
Other threads can call a thread’s join() method. This blocks the calling thread until the thread whose join() method is called is terminated.
After calling t.start() in main thread, the main thread will exit. Then the process is ended.
If you want to run the child thread forever or until it exits, you should call t.join() in main thread after t.start().