We use pyo3-log to get Rust logs into the Python logging framework; this seems to not work properly. If you put e.g. a warn!(...) then it doesn't print out anywhere.

We initialize the logging module in lib.rs:

And we import the synapse rust code very early in the Synapse process:

I think we're importing the rust code before the loggers are configured, which then causes pyo3-log to initialize and cache the Python logging configuration, then by the time we actually call Rust code we've reconfigured the python loggers, but that doesn't propagate into Rust.

I ran into this in unittests, but I think it would happen during normal usage as well.