Python3 and asyncio: how to implement websocket server as asyncio instance?

Question

I have multiple servers, each server is instance returning by asyncio.start_server. I need my web_server to works with websockets, to have possibility getting data using my javascript client. As I can see, asyncio do not provide websockets, only tcp sockets. Maybe I missed something ? I want to implement websocket server that I can using in asyncio.gather like below:

    loop = asyncio.get_event_loop()

    login_server = LoginServer.create()
    world_server = WorldServer.create()
    web_server   = WebServer.create()

    loop.run_until_complete(
        asyncio.gather(
            login_server.get_instance(),
            world_server.get_instance(),
            web_server.get_instance()
        )
    )

    try:
        loop.run_forever()
    except KeyboardInterrupt:
        pass

    loop.close()

I do not want to use aiohttp cause if using like in code above aiohttp just blocks another tasks. I need something that will be non-blocking and that will have access to data of another servers (login and world). Does it possible with asyncio ? Does asyncio provide something like websockets ? How to implement websocket server for using in asyncio.gather ?

Sergio Ivanuzzo · Accepted Answer · 2019-02-12 17:01:12Z

1

Well, finally I've implemented WebServer for using in another thread with asyncio. The code (WebServer code):

from aiohttp import web


class WebServer(BaseServer):

    def __init__(self, host, port):
        super().__init__(host, port)

    @staticmethod
    async def handle_connection(self, request: web.web_request):
        ws = web.WebSocketResponse()
        await ws.prepare(request)

        async for msg in ws:
            Logger.debug('[Web Server]: {}'.format(msg))

        return ws

    @staticmethod
    def run():
        app = web.Application()
        web.run_app(app, host=Connection.WEB_SERVER_HOST.value, port=Connection.WEB_SERVER_PORT.value)

And how to run:

executor = ProcessPoolExecutor()

loop.run_until_complete(
    asyncio.gather(
        login_server.get_instance(),
        world_server.get_instance(),
        loop.run_in_executor(executor, WebServer.run)
    )
)

answered Feb 12, 2019 at 17:01

Sergio Ivanuzzo

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1 Comment

user4815162342 Over a year ago

Running web.run_app with run_in_executor is an anti-pattern because it (unnecessarily) runs two event loops. You can use the AppRunner API instead, as shown in the first code snippet of this answer.

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