chore(python-sdk): Do not set log level directly in the SDK

[SupraSummus]

I noticed that the langfuse SDK sets the log level directly during initialization

https://github.com/langfuse/langfuse-python/blob/7d7e94127f7d469a0ec530820f3f7e407d663e3e/langfuse/client.py#L281-L282

It would be better to document the recommended logging level and let users configure it according to their needs rather than setting it directly in the SDK.

For example in a standard Django project, logging is typically configured before all the code is loaded. When I load the Langfuse SDK my config gets overridden.

Thank you for considering this suggestion.

[marcklingen]

Hi @SupraSummus, thanks for raising this. I've moved this to gh discussions as this is where we collect all ideas relating to improvements to langfuse.

@hassiebp wdyt? I see how this would impact other teams that want a very simple integration and would not appreciate to see all debug logs logged by the python sdk

[hassiebp]

The Langfuse Python SDK should only change it's own loggers log level and not any other modules log level. @SupraSummus if you have experienced anything differently, please let us know so we can address that :)

[SupraSummus]

@hassiebp Thank you for looking into this. My core issue is not about langfuse modifying loglevel of other modules, but about langfuse modifying its loglevel. I think langfuse sdk shouldn't touch logging configuration at all (except only when user demands it).

See this snippet:

import logging
from langfuse.decorators import observe


@observe
def sample_func():
    pass


logger = logging.getLogger('langfuse')
logger.setLevel(logging.ERROR)
print(logger)  # prints <Logger langfuse (ERROR)>

sample_func()
print(logger)  # prints <Logger langfuse (WARNING)>

This behavior is quite non-intuitive.

[SupraSummus]

My understanding is that this only sets the log level for "langfuse", how does this affect the rest of your application?

Yes, this only sets loglevel for langfuse.

My application needs to control the logging configuration. The logs are stored and then analyzed by dev team and I would like the logs to have the filtering the devs set in the project config. This is not specific to my usecase - this is common need to configure the logging at application level to gather things that matter.

When langfuse SDK sets its loglevel to some arbitrary value it is like saying "It doesn't matter what log level is set in the application config. Langfuse must run with WARNING loglevel, so here it is set and your config value is overridden. Silently."

[SupraSummus]

There is one more logger affected - httpx via clean_logger(). Langfuse sets its loglevel to WARNING during initialization.

[hassiebp]

Thanks @SupraSummus - created this issue to track progress: #5108