reload not working in tracing-subscriber v0.3.15

[cedricje]

Bug Report

Version

└── tracing-subscriber v0.3.15
    ├── tracing v0.1.36
    │   └── tracing-core v0.1.29
    ├── tracing-core v0.1.29 (*)
    └── tracing-log v0.1.3
        └── tracing-core v0.1.29 (*)

Platform

Linux LNMX-LPT005 5.4.0-125-generic #141-Ubuntu SMP Wed Aug 10 13:42:03 UTC 2022 x86_64 x86_64 x86_64 GNU/Linux

Crates

tracing-subscriber and/or tracing_log

Description

When reloading a filter i don't see the log records that were enabled by the filter.
This started with version v0.3.15 of the tracing-subscriber crate, v0.3.14 works.
The features tracing-log and env-filter are enabled on the tracing-subscriber crate

This is an example:

use tracing_subscriber::EnvFilter;
use tracing_subscriber::{fmt, prelude::*, reload};

fn main() {
    let filter = EnvFilter::from_default_env();
    let (filter, reload_handle) = reload::Layer::new(filter);

    tracing_subscriber::registry()
        .with(filter)
        .with(fmt::Layer::default())
        .init();

    reload_handle.reload("info").unwrap();
    log::error!("error trace");
    log::info!("info trace");
}

When running this with tracing-subscriber v0.3.15, error trace is shown, but not info trace. WIth eg. version v0.3.14 it shows info trace.

[hawkw]

Thanks for the report! My guess is that this is related to #2204, which is the only change between tracing-subscriber 0.3.14 and 0.3.15.

Do you know if this can be reproduced without actually reloading the reload layer? If the reload layer's filter is initially created with info enabled, and never reloaded, what events are shown?

[cedricje]

If i remove reload_handle.reload("info").unwrap(); and run it with RUST_LOG=info to have the initial filter set to info, it shows the info traces.

Another thing i've noticed is when using tracing::info! isof log::info! it does show the info traces as expected.

[cedricje]

From what i could see tracing_log::log_tracer::Builder::init calls log::set_maxlevel(LevelFilter::Error).
With the previous version of tracing-subscriber this was log::set_maxlevel(LevelFilter::Trace).

Should this be set to log::LevelFilter::max() and let log_tracer filter based on the level?

[jimmyH]

Issue still exists on tracing-subscriber v0.3.18.

Looks like the maximum level is set when the tracing-subscriber is initialized and you can never increase it above this level when you reload ie if you initialize with Level::INFO you can decrease it with reload() but can never increase above Level::INFO.

Workaround:

• Initialize with Level::TRACE
• Then you can use reload() to dynamically change the trace level to whatever you want.