Dynamically change log level in the file

[phungleson]

Hi,

Thanks again for logforth.

I wonder if I can enable log for a file, i.e. at the top of the file I want to say log_level!(DEBUG), so it will add to the global configuration.

I understand that I can change that at env level, or when I init the log, but when we have lots of files, it is difficult to get the correct module of the file to enable the log.

Thanks,

[tisonkun]

I'll consider this. It may requrie a new logging API that I'm thinking of making an analogy of slf4j in Rust.

Implementing the feature is straightforward, but I may need some time to consider how to work with existing ecosystem.

[tisonkun]

@phungleson As a workaround, you can write something like:

• Define a filter that based on a global state with module settings
• When logging in a module, obtain a logger from a function, while at the beginning of that function, update the global filter state.

log supports log::info!(logger: l, ...) so it should be fluent.

I'll try to find a proper API design and add examples, but it can take some time.

[phungleson]

Thanks for the suggestion, my use case is a bit more elaborate than a function.

Normally I have a Component with various interactive functions can be called during rendering cycle, so normally I would like to enable DEBUG for that Component/file. It is helpful to see how Component#fns are called and the sequencing of them.

[tisonkun]

For this dedicated use case, I think you can use some global registry like https://github.com/dtolnay/inventory or ctor and leverage a custom filter.

Then you develop some code snippet like

#[ctor::ctor]
unsafe fn set_file_level() {
  GLOBAL_FILTER.set_module_level(module_path!(), DEBUG);
}

fn main() {
  logforth::starter_log::builder()
    .dispatch(|d| d.filter(GLOBAL_FILTER))
    .apply();
}

I may try to make an example local crate to demonstrate it. Feel free to ping me in April if I failed to find time to do so then.

[phungleson]

Thanks, I managed to make it work. Have to define a new Filter though, not sure it is intended that way.

If you like I can quickly add a PR.

[tisonkun]

If you like I can quickly add a PR.

I'm glad to review your PR and see how it works. If it's desirable I can integrate it in logforth or share it as a common example ;D