tracing-elastic-apm does not work without a global subscriber about tracing-elastic-apm HOT 8 CLOSED

After registering layers, you should call init().

tracing_subscriber::registry()
        .with(stdout_layer)
        .with(another_layer)
        .with(another_another_layer)
        .with(tracing_elastic_apm_layer)
        .init();       // you should call init here

from tracing-elastic-apm.

@krojew
Calling init() sets the subscriber as the global default one which is exactly what I don't want to do. This issue is indeed about the fact that the tracing-elastic-apm works when the subscriber is global but it does not work when using a default non-global one:

let _guard = tracing::subscriber::set_default(subscriber);

from tracing-elastic-apm.

What other layers you found working in such case?

from tracing-elastic-apm.

This is a small snippet of our real code:

        // Log to a file
        let file_appender = tracing_appender::rolling::never(dir, filename);
        let (non_blocking, guard) = tracing_appender::non_blocking(file_appender);
        let file_layer = Layer::new().with_ansi(false).with_writer(non_blocking);

        // Log to stdout
        let (non_blocking, stdout_guard) = tracing_appender::non_blocking(std::io::stdout());
        let stdout_layer = Layer::new().with_ansi(false).with_writer(non_blocking);

    let subscriber = tracing_subscriber::registry()
        .with(env_filter) // EnvFilter
        .with(file_layer) 
        .with(apm_layer)
        .with(stdout_layer);

everything works except the apm_layer.

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Can you try calling set_default() directly on subscriber, rather than tracing::subscriber::set_default(subscriber)?

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Tried, the issue is still present.

from tracing-elastic-apm.

After some investigation, it looks like https://docs.rs/tracing-subscriber/0.2.20/tracing_subscriber/fmt/struct.Layer.html works a bit differently than this crate. It's hard to tell if this is the reason, or if any of those two behaviors is wrong. If you use with_writer, everything that happens to spans gets converted to events and written to given writer (https://docs.rs/tracing-subscriber/0.2.20/src/tracing_subscriber/fmt/fmt_layer.rs.html#587). tracing-elastic-apm, on the other hand, distinguishes between events and spans, and sends span data only when a span gets closed.

Therefore we're left with some open questions:

• Is this the reason for this behavior?
• Is fmt::Layer implementation actually correct?

It's possible you found either a bug or undocumented behavior in tracing-subscriber. I'm not sure if there's anything I can do in this case.

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@krojew
After in-depth investigations, we found that the issue is not in this crate but, somehow, in tracing-actix-web that does not log the HTTP request info when the subscriber is not global.

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