Drop user supplied loop

[asvetlov]

For sake of #2530

The mode is exists for not closing the loop for sake of later reusage, I believe we can invite more robust way by #2530

[kxepal]

So now we always use asyncio global loop and if I want/need to run an app in different one, I should run it in different thread?

[codecov-io]

Codecov Report

Merging #2531 into master will decrease coverage by <.01%.
The diff coverage is 75%.

@@            Coverage Diff             @@
##           master    #2531      +/-   ##
==========================================
- Coverage   97.13%   97.13%   -0.01%     
==========================================
  Files          39       39              
  Lines        8070     8059      -11     
  Branches     1415     1411       -4     
==========================================
- Hits         7839     7828      -11     
  Misses         99       99              
  Partials      132      132

Impacted Files	Coverage Δ
aiohttp/web.py	98.92% <75%> (-0.05%)	⬇️

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[asvetlov]

Running two loops in parallel in the same thread is impossible, isn't it?
The program should run one loop per thread (except unittest case), most likely the single loop in main thread per process.

[donkahuna]

If I want to change the loop, for example use uvloop ? How can I do this ?

[asvetlov]

https://docs.python.org/3/library/asyncio-eventloops.html#asyncio.set_event_loop_policy

[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