3.3.0 broken - switching from asyncio.get_event_loop() to asyncio.run() causing major issues

[Zippy1999]

In version 3.2.0, calls to get the running event loop were executed with asyncio.get_event_loop / run_until_complete

In version 3.3.0 asyncio.run() has been used instead. This closes the running event loop after the code is executed.

When using this in lambda code which needs to run asyncio.get_event_loop it causes subsequent executions to fail

The failure errors:

ersions/3.11.9/lib/python3.11/asyncio/events.py", line 683, in get_event_loop
    raise RuntimeError('There is no current event loop in thread %r.'
RuntimeError: There is no current event loop in thread 'MainThread'.

The changed code is in __init__.py in the metric_scope decorator.

[Zippy1999]

Running code in aws lambda with python 3.11 runtime

[SamStephens]

@Zippy1999 are you using the hack I documented in this issue?

@metric_scope
def handler(event, context, metrics):
    try:
        # Actual handler logic
    finally:
        # Need to call flush like this because it's a coroutine/asynchronous
        loop = asyncio.get_event_loop()
        loop.run_until_complete(metrics.flush())

Because it looks like the change in 3.3.0 broke this hack - in which case I think the right thing to do is remove the hack.

[Zippy1999]

@SamStephens thanks for responding 👍

I've checked the code in the affected lambda - we are not currently implementing this hack.

I know that run() would be the preferred one to use especially given that get_event_loop() is being deprecated.

I am investigating to see how much work it would be to move to replace any instances of get_event_loop() / get_running_loop() with asyncio.run() in the lambda affected. This could potentially be problematic though as I know of at least one dependency which the lambda uses which utilises get_running_loop()

I know we can't stop progress nor would I want to 😆 - but a small warning on the release notes of 3.3.0 may be helpful to others of a potential "breaking" change? 😅

[SamStephens]

@Zippy1999 sorry, I missed that you're using asyncio.get_event_loop in your code - my bad.