This is a backport from cpython 3.12
https://docs.python.org/3/library/asyncio-policy.html
> PidfdChildWatcher is a “Goldilocks” child watcher implementation. It doesn’t require signals or threads, doesn’t interfere with any processes launched outside the event loop, and scales linearly with the number of subprocesses launched by the event loop. The main disadvantage is that pidfds are specific to Linux, and only work on recent (5.3+) kernels.
https://github.com/python/cpython/pull/98024
There are some additional fixes in cpython 3.12
in https://github.com/python/cpython/pull/94184
when there is no event loop running in the main thread
but this is not a problem we have
The default on python 3.8 is for max_workers is significantly
lower than the default on python 3.7 which means we can get starved
for workers.
To determine a reasonable maximum, the maximum was increased to large
number on 5 production instances.
The number of worker threads created during startup that were
needed to avoid waiting for a thread:
HOU 1 - 71
HOU 2 - 48
OGG 1 - 60
OGG 2 - 68
OGG 3 - 64
This lead to a selection of 64 as it was reliable in all cases
and did not have a significant memory impact
J. Nick Koston