Peers are being dropped when running Tribler on Windows

[devos50]

After our upgrade to Python 3.8, it seems that shortly after starting Tribler, peers are being dropped. The debug panel shows a few peers, but after a few minutes, these peers are gone. Anonymous downloads/TrustChain introduction requests are failing after around one minute.

Observations:

• This happens both when running Tribler from source on our Windows building machine as well as running it from a frozen environment.
• I have seen it both on 32-bit and 64-bit.

[devos50]

After some extensive testing, it seems to occur when the ProactorEventLoop is used, which is the default loop in Python 3.8. I would suggest to fallback to the SelectorEventLoop for now, until we debugged/investigated the bug further.

[egbertbouman]

Nice, good to hear my tip seems to have worked!

[ichorid]

🤦 🤕

[egbertbouman]

UDP support was only added recently to ProactorEventLoop (see https://bugs.python.org/issue29883), so maybe there are still some issues with it?

[qstokkink]

I would suggest to fallback to the SelectorEventLoop for now, until we debugged/investigated the bug further.

The only downside I see to using the SelectorEventLoop is that it does not support Windows pipes (which we don't use) and doesn't use Windows IOCP, which is a bit better for multicore event handling.

I'd vote for just using SelectorEventLoop for the foreseeable future, without further debugging/investigating the ProactorEventLoop.

[ichorid]

Reopened #5435. That's the downside.

[qstokkink]

Ok, in that case I guess it's still worth it to try and get the ProactorEventLoop up and running.

[devos50]

Given that the SelectorEventLoop seems to still work, I do not consider this as a blocker for the 7.5.2 release anymore.

[ichorid]

Haven't seen this in awhile