Update fake_server.py example/ provide full example how to create truly asynchronous server

[jsdevtom]

Long story short

https://github.com/aio-libs/aiohttp/blob/master/examples/fake_server.py#L37 is outdated.

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

run_app() provides a simple blocking API for running an Application.
For starting the application asynchronously or serving on multiple HOST/PORT AppRunner exists.

No up to date example exists however on how exactly to implement the truly async server

Expected behaviour

Replicating the example doesn't cause DeprecationWarning: loop argument is deprecated

Actual behaviour

Replicating the example causes DeprecationWarning: loop argument is deprecated

Steps to reproduce

Replicating the example found linked above. Or in my exact case:

server.py

import asyncio

from multidict import MultiDictProxy
from aiohttp import web

routes = web.RouteTableDef()
loop = asyncio.get_event_loop()


class Server:

    def __init__(self, *, inner_loop):
        self.loop = inner_loop
        self.app = web.Application(loop=loop)
        self.app.add_routes(routes)
        self.runner = None

    async def start(self):
        port = 40509
        self.runner = web.AppRunner(self.app)
        await self.runner.setup()
        site = web.TCPSite(self.runner, port=port)
        await site.start()

    @routes.get('/')
    async def on_query(self, request):
        query: MultiDictProxy = request.query.get('q')

        await asyncio.sleep(5)

        if query:
            return web.json_response({'query': query})

        return web.json_response({})


async def main(main_loop):
    server = Server(inner_loop=main_loop)
    await server.start()


try:
    loop.run_until_complete(main(loop))
except KeyboardInterrupt:
    loop.close()

requirements.py

pythonwhois==2.4.3
aiohttp==3.5.4
cchardet==2.1.4
aiodns==2.0.0

Dockerfile

FROM python:3.7.3
WORKDIR /app
COPY ./requirements.txt /app
COPY ./server.py /app
RUN pip install -r ./requirements.txt
CMD ["python", "/app/server.py"]

Then run docker build . -t py-whois && docker run py-whois

Your environment

Docker image python:3.7.3-alpine3.9 (see above)

[asvetlov]

Keeping examples up to date is important, I agree.
Pull request to fix them are welcome!
I have questions for your snippet though:

1. loop should be avoided. Early binding a loop on module level is a bad practice.
2. Replace loop.run_until_complete() with asyncio.run() to follow best practices.
3. IMHO Server.start() finishes just after the server creation. Need to add something to serve incoming requests for more long time
4. RouteTableDef doesn't support methods in decorators.

[jsdevtom]

Thank you for the prompt response. Points 3 and 4 I realized later but 1 and 2 I didn't realize thanks for the knowledge!

[mjpieters]

The example has been updated to remove the loop argument in #3580. Are there other updates needed still?

[mjpieters]

We’ve confirmed this is covered now.