How to run an aiohttp server in a thread?

Question

This example of aiohttp server in a thread fails with an RuntimeError: There is no current event loop in thread 'Thread-1'. error:

import threading
from aiohttp import web


def aiohttp_server():
    def say_hello(request):
        return web.Response(text='Hello, world')

    app = web.Application(debug=True)
    app.add_routes([web.get('/', say_hello)])
    web.run_app(app)


t = threading.Thread(target=aiohttp_server)
t.start()

How to run a aiohttp server in thread?

Maybe this example will help you: stackoverflow.com/questions/54650760/… — Sergio Ivanuzzo
– Sergio Ivanuzzo, Commented Feb 13, 2019 at 13:05

Sraw · Accepted Answer · 2019-08-20 09:24:58Z

7

Create handler in main thread and manually create an event loop in child thread.

import asyncio
import threading
from aiohttp import web


def aiohttp_server():
    def say_hello(request):
        return web.Response(text='Hello, world')

    app = web.Application(debug=True)
    app.add_routes([web.get('/', say_hello)])
    handler = app.make_handler()
    return handler


def run_server(handler):
    loop = asyncio.new_event_loop()
    asyncio.set_event_loop(loop)
    server = loop.create_server(handler, host='127.0.0.1', port=8089)
    loop.run_until_complete(server)
    loop.run_forever()


t = threading.Thread(target=run_server, args=(aiohttp_server(),))
t.start()

Update

For new aiohttp, use the following, thank @Auyer for notification.

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()

edited Aug 20, 2019 at 9:24

answered Jul 31, 2018 at 9:43

Sraw

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6 Comments

bux Over a year ago

This example code don't include thread usage example. How can i test it with thread ?

bux Over a year ago

You mean like that 0bin.net/paste/… ? It produce RuntimeError: set_wakeup_fd only works in main thread error.

Sraw Over a year ago

Well, you are right. We have to create handler in main thread and then use child thread to execute loop. I will update my answer.

user4548084 Over a year ago

Whether you'd do this in the case of threading or not, I dont know, however you can use an async def before the say_hello to have it async. The make_handler is very useful! This helped solve another issue.

Auyer Over a year ago

DeprecationWarning: Application.make_handler(...) is deprecated, use AppRunner API instead. I'm looking for a solution for this warning, and will post her if I find it.

|

Heron Rossi · Accepted Answer · 2019-05-17 17:57:15Z

3

There's a new API intended for this use case:

https://docs.aiohttp.org/en/stable/web_advanced.html#application-runners

from aiohttp import web
import asyncio


async def healthz(request):
    return web.Response(text="OK")

app = web.Application()
app.add_routes([web.get("/", healthz)])


async def runner():
    runner = web.AppRunner(app)
    await runner.setup()
    site = web.TCPSite(runner, "localhost", 8080)
    await site.start()


loop = asyncio.get_event_loop()
loop.run_until_complete(runner())

answered May 17, 2019 at 17:57

Heron Rossi

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Comments

user4815162342 · Accepted Answer · 2018-08-01 09:38:35Z

2

We must use app.make_handler handler in main thread, example:

import asyncio
import threading
from aiohttp import web

loop = asyncio.get_event_loop()


def say_hello(request):
    return web.Response(text='Hello, world')


app = web.Application(debug=True)
app.add_routes([web.get('/', say_hello)])

handler = app.make_handler()
server = loop.create_server(handler, host='127.0.0.1', port=8080)


def aiohttp_server():
    loop.run_until_complete(server)
    loop.run_forever()


t = threading.Thread(target=aiohttp_server)
t.start()

edited Aug 1, 2018 at 9:38

user4815162342

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answered Jul 31, 2018 at 9:32

bux

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5 Comments

Sraw Over a year ago

Is this a part of question? You shouldn't add an answer instead of editing question.

tevemadar Over a year ago

You are "abusing" the event loop of the main thread, which may work in a simple test code, but it is not a good idea in general. Either create one yourself (as in @Sraw's answer) or just call get_event_loop() from inside the thread (according to its source code it will create a new event loop for the thread in this case)

Sraw Over a year ago

@tevemadar get_event_loop() will only create a new event loop in main thread, see this condition: isinstance(threading.current_thread(), threading._MainThread)

tevemadar Over a year ago

@Sraw oops, I thought it was an inner if

bux Over a year ago

@Sraw no, it is a response of question.

user202729 · Accepted Answer · 2020-01-01 12:28:44Z

1

It's possible to use web.run_app, just create a new event loop (and set handle_signals=False to avoid RuntimeError: set_wakeup_fd only works in main thread):

import threading
import asyncio
from aiohttp import web

def aiohttp_server():
    def say_hello(request):
        return web.Response(text='Hello, world')

    asyncio.set_event_loop(asyncio.new_event_loop())  # create a new event loop here
    app = web.Application(debug=True)
    app.add_routes([web.get('/', say_hello)])
    web.run_app(app, handle_signals=False)

answered Jan 1, 2020 at 12:28

user202729

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