Serving static files with add_static() breaks event loop on windows

[major12]

Long story short

Serving big static file makes impossible to process new requests at this time. Event loop does not pass execution to other coroutines.
If client stops to receive file in the middle of transfer then server becomes broken - it cannot receive/process new requests.

Expected behaviour

Other requests can be processed while file is served.

Actual behaviour

Server hangs for some time or becomes broken forever.

Steps to reproduce

Server:

from aiohttp import web

def index(request):
    return web.Response(text='hello world')

app = web.Application()
app.router.add_get('/', index)
app.router.add_static('/static/', path=str('./test/'))
web.run_app(app)

Client:

import asyncio
from aiohttp import ClientSession

async def download(file):
    async with ClientSession() as session:
        async with session.get(file) as resp:
            while True:
                data = await resp.content.read(1000)
                if not data:
                    break
                await asyncio.sleep(1)

loop = asyncio.get_event_loop()
loop.run_until_complete(download('http://127.0.0.1:8080/static/1.mkv'))
loop.close()

1. Copy your favourite movie to test/1.mkv
2. Run server
3. Try to fetch page http://127.0.0.1:8080/
4. Run client
5. Try to fetch page http://127.0.0.1:8080/ one more time

Your environment

aiohttp (1.1.3)
Python 3.5.2 (v3.5.2:4def2a2901a5, Jun 25 2016, 22:18:55) [MSC v.1900 64 bit (AMD64)] on win32
Win10

[asvetlov]

Well, sendfile should use aiofiles in fallback code.
sendfile already works in async manner.

[major12]

After small print-debugging session I found the issue
https://github.com/KeepSafe/aiohttp/blob/master/aiohttp/file_sender.py#L132
Instead of

                count = count - chunk_size
                if count <= 0:
                    break
                chunk = fobj.read(count)

there should be

                count = count - chunk_size
                if count <= 0:
                    break
                chunk = fobj.read(chunk_size)

Could you please include the fix in next release.

[asvetlov]

Excellent catch!
Fixed by aiohttp 1.1.5

[lock]

This thread has been automatically locked since there has not been
any recent activity after it was closed. Please open a new issue for
related bugs.

If you feel like there's important points made in this discussion,
please include those exceprts into that new issue.