Debugging+Logging: find out when sync function run in asynq context

[LiraNuna]

As we migrate our code to use asynq, we would love a way to detect usages of sync calls within asynq contexts.

For example, imagine:

@asynq.async()
def data_fetch_1():
    return 5

@asynq.async()
def data_fetch_times_2():
    data = data_fetch_1()
    return data + data

This will incur a sync fetch within an already asynq call which should be fixed since it incurs performance penalties especially when data_fetch_2 is batched.

I have not seen a way to log/debug/add a hook to figure out when this happens

[JelleZijlstra]

Is Manan's addition in #31 sufficient for your use case?

[LiraNuna]

How can this be turned on?

[manannayak]

if you set options.DUMP_SYNC_CALLS to True in debug.py, you should see a message in stdout every time an async function is called synchronously inside another async function.

[LiraNuna]

I'm guessing like this? If so, this is great, thank you!

from asynq.debug import options

options.DUMP_SYNC_CALLS = True

[manannayak]

Yep

[JelleZijlstra]

We should really document that options mechanism.