There are no examples of how to set log level per module

[wlinna]

I have been fighting and trying to figure out how to do something like this with logforth:

    simple_logger::SimpleLogger::new()
        .with_module_level("geo", lib::log::LevelFilter::Warn)
        .with_module_level("rerun", lib::log::LevelFilter::Warn)
        .with_module_level("re_chunk", lib::log::LevelFilter::Warn)
        .with_module_level("re_log", lib::log::LevelFilter::Warn)
        .with_module_level("re_log_encoding", lib::log::LevelFilter::Warn)
        .with_module_level("re_sdk", lib::log::LevelFilter::Warn)
        .with_module_level("re_sorbet", lib::log::LevelFilter::Warn)
        .with_module_level("tracing", lib::log::LevelFilter::Warn)
        .init()
       .unwrap();

I went through all the examples, but none of them show how to do this.

Eventually I found EnvFilter, but even that doesn't have examples.

[tisonkun]

Thanks for reporting this!

I can add some examples later, or I'm glad to review patches to add some if you provide :D

[wlinna]

Thanks. I'm still trying to figure this out though. I think I might have had some success. I tried creating my filter like this:

    EnvFilterBuilder::from_default_env()
        .filter_level(LevelFilter::All)
        .filter_module("geo", LevelFilter::MoreSevereEqual(logforth::record::Level::Warn))
        .filter_module("rerun", LevelFilter::MoreSevereEqual(logforth::record::Level::Warn))
        .filter_module("re_chunk", LevelFilter::MoreSevereEqual(logforth::record::Level::Warn))
        .filter_module("re_log", LevelFilter::MoreSevereEqual(logforth::record::Level::Warn))
        .filter_module("re_log_encoding", LevelFilter::MoreSevereEqual(logforth::record::Level::Warn))
        .filter_module("re_sdk", LevelFilter::MoreSevereEqual(logforth::record::Level::Warn))
        .filter_module("tracing", LevelFilter::MoreSevereEqual(logforth::record::Level::Warn))
        .build()

EDIT: I was wrong. One of the modules is missing from the list above.

but it seems like LevelFilter::All takes precedence over everything (i.e. nothing gets filtered in the end). Is there a good wway to set debug/trace level filter for everything except these uninteresting modules here?

[tisonkun]

@wlinna Change the configure order should work, i.e., put .filter_level(LevelFilter::All) to the end before .build().

[wlinna]

Thanks for the quick response. However, this code:

    EnvFilterBuilder::from_default_env()
        .filter_module("lib", LevelFilter::MoreSevereEqual(logforth::record::Level::Debug))
        .filter_module("geo", LevelFilter::MoreSevereEqual(logforth::record::Level::Warn))
        .filter_module("rerun", LevelFilter::MoreSevereEqual(logforth::record::Level::Warn))
        .filter_module("re_chunk", LevelFilter::MoreSevereEqual(logforth::record::Level::Warn))
        .filter_module("re_log", LevelFilter::MoreSevereEqual(logforth::record::Level::Warn))
        .filter_module("re_log_encoding", LevelFilter::MoreSevereEqual(logforth::record::Level::Warn))
        .filter_module("re_sdk", LevelFilter::MoreSevereEqual(logforth::record::Level::Warn))
        .filter_module("tracing", LevelFilter::MoreSevereEqual(logforth::record::Level::Warn))
        .filter_level(LevelFilter::All)
        // This doesn't solve my problem either
        //   .filter_level(LevelFilter::MoreSevereEqual(logforth::record::Level::Trace))   
        .build()

didn't work. Those re crates flood my console as long as .filter_level(LevelFilter::All) is anywhere in that builder.

Here is how I initialize logforth:

    logforth::starter_log::builder()
        .dispatch(|d| d.filter(make_log_filter()).append(append::Stdout::default()))
        // .dispatch(|d| d.filter(make_log_filter()).append(append::FastraceEvent::default()))
        .apply();

[tisonkun]

@wlinna You can try removing .filter_level(LevelFilter::All) and keep other filter_modules.

If that doesn't work, could you provide some log entries that you'd expect to be filtered or accepted?

The current EnvFilter does have some limitation to represent early accept logic:

impl Filter for EnvFilter {
    fn enabled(&self, criteria: &FilterCriteria, _: &[Box<dyn Diagnostic>]) -> FilterResult {
        let level = criteria.level();
        let target = criteria.target();

        // search for the longest match, the vector is assumed to be pre-sorted
        for directive in self.directives.iter().rev() {
            let name = directive.name.as_deref();
            if name.is_none_or(|n| target.starts_with(n)) {
                // longest match wins; return immediately
                return if directive.level.test(level) {
                    FilterResult::Neutral
                } else {
                    FilterResult::Reject
                };
            }
        }

        FilterResult::Reject
    }
}

[tisonkun]

LevelFilter::All means "Enable all levels" while LevelFilter::Off means "Disable all levels". There can be some language bias on the naming, though.

[wlinna]

Leaving filter_level does make the traces from the specified crates disappear, which is good, but I have two issues with it:

• The default log-level is no longer explicit
• I will have to configure every other crate too

LevelFilter::All means "Enable all levels" while LevelFilter::Off means "Disable all levels". There can be some language bias on the naming, though.

I think it's clear enough. After all, in Rust iterators filter keeps those which elements for which the predicate returns true.

[wlinna]

Good news. LevelFilter::ALL either at the beginning or the end works for me after all. The reason why it seemed to not work is that I left one of the modules out for some reason. (Weird given that I used "multiple cursors" technique to copy all of them, and yet this one was left out)

// My original simple_logger code had this
        .with_module_level("re_sorbet", lib::log::LevelFilter::Warn)

But my logforth filter configuration did NOT. I didn't notice it earlier because re_sorbet made such huge log entries that I had trouble seeing where the log even originated.

Thanks a lot for your attention. This week I will contribute my configuration as an example for per-module log level filtering.