Logging forwarding unconditionally sends logs to subscriber without checking if enabled

[torkleyy]

The default tracing-subscriber with say an env filter will log them irrespective of the configuration.

[DAIMENGEN]

Hi, I took some time to investigate this issue and wanted to share what I found.

In the llama-cpp-rs project, the simple implementation initializes the subscriber using:

tracing_subscriber::fmt().init();

From what I’ve learned, this form of initialization does not respect the RUST_LOG environment variable by default. It sets the maximum log level to INFO, and changing the log level using something like RUST_LOG=warn won’t take effect in this case.

To enable dynamic log level configuration via environment variables, you should initialize the subscriber like this instead:

tracing_subscriber::fmt::init();

So, I'm not sure whether you’re using the former (tracing_subscriber::fmt().init()) in your setup — but if so, that might explain the behavior you’re seeing.

Hope this helps!

[DAIMENGEN]

Hi again! I've submitted a pull request that I believe addresses this issue: #760

The PR improves the logging behavior by performing early log-level filtering, which avoids unnecessary log generation when a level is disabled. It also ensures that the RUST_LOG environment variable works as expected (if applicable).

Feel free to review it — I'm happy to adjust it based on your feedback!