How to modify EnvFilter instead of replace

[wuanzhuan]

in tracing_subscriber 0.3.18

I use a Envfilter in global subscriber. It is composed of one LevelFilter and Targets. When i modify the level filter, i need replace the entire EnvFilter. How do I only modify the LevelFilter in EnvFilter.

[kaffarell]

Could you post a snippet? Also checkout https://docs.rs/tracing-subscriber/latest/tracing_subscriber/reload/index.html#examples. This should be possible if I understand your issue correctly.

[wuanzhuan]

@kaffarell I use the envfilter. Because of it can easy to "and" tow filter. I use one global level filter and some target filter in a env filter.
And i just want to modify the global level filter or one target filter. how to do it?

    // trace init:
    let subscriber = tracing_fmt::fmt()
        .with_timer(tracing_fmt::time::LocalTime::rfc_3339())
        .with_file(true)
        .with_line_number(true)
        .with_writer(non_blocking)
        .with_ansi(false)
        .with_env_filter(format!("info,sys_monitor::event_trace::stack_walk=debug")) // env filter
        .with_filter_reloading();
    let reload_handle = subscriber.reload_handle();
    subscriber.init();

//==================
   
   // How to modify env filter like this:
   reload_handle.modify(|filter| *filter = filter::LevelFilter::DEBUG);

[kaffarell]

AFAIK editing the EnvFilter directly is not possible, but you can create a layer with multiple filters! For example something like this should work:

    let filter = filter::LevelFilter::WARN;
    let (filter, reload_handle) = reload::Layer::new(filter);

    let layer = tracing_subscriber::fmt::layer()
        .with_timer(tracing_subscriber::fmt::time::LocalTime::rfc_3339())
        .with_file(true)
        .with_line_number(true)
        .with_ansi(false)
        .with_filter(EnvFilter::new("trace,sys_monitor::event_trace::stack_walk=debug"))
        .with_filter(filter);

    tracing_subscriber::registry().with(layer).init();

    let _ = reload_handle.modify(|filter| *filter = filter::LevelFilter::DEBUG);