Using tracing_appender nothing is printed in terminal, why?

[frederikhors]

Bug Report

This code doesn't print anything on my terminal:

use tracing::info;

fn main() {
  init();

  info!("test me");

  println!("i should have info! message before this")
}

pub fn init() {
  let (non_blocking, _guard) = tracing_appender::non_blocking(std::io::stdout());

  tracing_subscriber::fmt()
    // .with_writer(non_blocking) // with this info! is not printed
    .init();
}

Version

tracing = { version = "0.1.36", features = ["log"] }
tracing-subscriber = { version = "0.3.15", features = ["env-filter"] }
tracing-log = "0.1.3"
tracing-appender = "0.2.2"

Platform

Windows 10 64

[hawkw]

Your init function is dropping the WorkerGuard returned by calling tracing_appender::non_blocking when it exits. Dropping this guard shuts down the non-blocking appender's worker thread, so the worker thread shuts down when your init function returns.

You can fix this by changing your code to return the guard from init and hold it in your main function, like this:

use tracing::info;

fn main() {
  let _guard = init();

  info!("test me");

  println!("i should have info! message before this")
}

pub fn init() -> impl Drop {
  let (non_blocking, guard) = tracing_appender::non_blocking(std::io::stdout());

  tracing_subscriber::fmt()
    .with_writer(non_blocking) 
    .init();

  guard
}