ClientSession.request unexpectedly cancels task on timeout

[savv]

Long story short

await client.get('https://httpbin.org/delay/10', timeout=.1)
This call throws an exception on timeout, and it cancels the task it's running in.
This makes it hard to handle timeouts locally, e.g. by catching the timeout and returning an alternate value.

It would at least be worth documenting this behavior.

Expected behaviour

I would have liked/expected the sample below to print:
Caught exception! api_req was able to handle timeout.

Actual behaviour

Caught exception! aiohttp cancelled us

Steps to reproduce

import aiohttp
import asyncio

loop = asyncio.get_event_loop()
client = aiohttp.ClientSession(loop=loop)

async def api_req():
    try:
        res = await client.get('https://httpbin.org/delay/10', timeout=.1)
    except asyncio.TimeoutError:
        print('Caught exception!')
        return False
    except:
        print('This should not happen.')
    return True

async def arun():
    done, not_done = await asyncio.wait([api_req()])
    done, = done
    try:
        assert done.result() == False
        print('api_req was able to handle timeout.')
    except asyncio.CancelledError:
        print('aiohttp cancelled us')
    except:
        print('This should not happen.')

loop.run_until_complete(arun())
client.close()
loop.close()

Your environment

python 3.6.2 on osx

[hellysmile]

can You use just asyncio.TimeourError instead of asyncio.CancelledError?

[savv]

That still won't let me handle the time out within api_req

[savv]

@hellysmile FYI I updated the code snippet to include except: print('This should not happen.'). It still prints exactly the same thing, but now it's clearer which part of the code throws which exception.

One solution would be not to catch the TimeoutError inside of api_req() and let it propagate to arun(), then handle it there. I think this would be a suboptimal solution, because it prevents api_req() from gracefully handling the timeout and returning an alternate value (e.g. a default value).

[wojunnihou]

I meet the same issues!!!!!
Python 3.5.2 on centos

async def ceshi(request, *args, **kwargs):

    # url = "https://stackoverflow.com/jobs?med=site-ui&ref=jobs-tab"
    url = 'https://api.github.com/events'
    url = 'https://www.baidu.com'
    try:
        async with aiohttp.ClientSession(conn_timeout=5,read_timeout=10) as session:
            async with session.get(url,timeout=5) as resp:
                print(resp.status)
                data = await resp.text()
                return HTTPResponse(data)
    except:
        return HTTPResponse("error", status=400)

[argaen]

@savvopoulos @wojunnihou I cannot reproduce:

23:04 $ python timeout.py 
Caught exception!
api_req was able to handle timeout.

timeout.py is the script uploaded by @savvopoulos

[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].
[new issue]: https://github.com/aio-libs/aiohttp/issues/new