[BUG] Logging level debug does not work in local or portal logs

Investigative information

Please provide the following:

In any python function, log level debug does not display in both local and portal logs.

Repro steps

Provide the steps required to reproduce the problem:

Expected behavior

Provide a description of the expected behavior.

Actual behavior

Provide a description of the actual behavior observed.

Known workarounds

Provide a description of any known workarounds.

Contents of the requirements.txt file:

Provide the requirements.txt file to help us find out module related issues.

Related information

Provide any related information

• Links to source
• Bindings used

[vrdmr]

@Hazhzeng

When the worker process is created, the host is not passing --log-level flag into the argument, thus the Python worker will only emit the INFO log into console. https://github.com/Azure/azure-functions-python-worker/blob/dev/azure_functions_worker/main.py#L21

How do we configure debug logging for workers logs from the host side? Is there an app setting that the host can pass in?

[Hazhzeng]

Thanks @pragnagopa, @vrdmr and @stefanushinardi for the offline sync up. We determine that there’re two places blocking the logging from emitting debug level logs:

1. When the worker process is created, the host is not passing --log-level flag into the argument, thus the Python worker will only emit the INFO log into console. https://github.com/Azure/azure-functions-python-worker/blob/dev/azure_functions_worker/main.py#L21
2. After the worker establishes GRPC channel to the host, the root logger will stop using console log and switch to GRPC log which is pinned to INFO https://github.com/Azure/azure-functions-python-worker/blob/dev/azure_functions_worker/dispatcher.py#L125

Since the GRPC logging handler is attached onto the root logger, currently we have a concern on the performance when dropping the INFO level constrain, since some third-party libraries are using DEBUG level logs (e.g. azure-storage-blob https://github.com/Azure/azure-sdk-for-python/blob/master/sdk/storage/azure-storage-blob/azure/storage/blob/_shared/policies.py#L201-L203).