Feature: Add logging setup instructions to DEVELOPER.md

[alexzaitsev]

Describe desired feature

It would be great if DEVELOPER.md doc contained some information on how logging is set up and how to configure it.

For example, I see SimpleLogger in the main.rs. I tried to change LevelFiler to LevelFilter::Debug but this still show all debug logs across the project.

    SimpleLogger::new()
        .with_level(LevelFilter::Warn)
        .with_module_level("simln_lib", cli.log_level)
        .with_module_level("sim_cli", cli.log_level)
        .init()
        .unwrap();

Example of the logs that are not shown:

• file: lib.rs
• fn: produce_events
• log: log::debug!("Generated payment: {source} -> {}: {amount} msat.", destination);
  As a workaround, I have to change log::debug! to println! but this won't work in the long run.

Use case for feature

It will help a lot for all new folks who want to contribute.

Would you like to contribute code for this feature?

[carlaKC]

Could you explain what you were looking to achieve here? IIUC you wanted to turn on debug logging only for the produce_events function in lib.rs?

I think it's pretty standard for a logging library to only allow setting log level per-module, and the SimpleLogger docs are sufficient to explain that IMO.

[alexzaitsev]

I'd like just to see debug logs where they already are. I followed SimpleLogger docs but wasn't able to set up this as it's described above.

[carlaKC]

Oh, well by default we're setting those to info but you can run the program with -l debug to change the log level?

sim-cli --help:

  -l, --log-level <LOG_LEVEL>
          Level of verbosity of the messages displayed by the simulator.
          Possible values: [off, error, warn, info, debug, trace] [default: info]