How to enable logging in Poem

Question

I am using poem-web, a rust library for building http based services but I have not been able to figure out how to enable logging so I can see why a POST endpoint is failing with Bad Request Error. It is due to deserialisation issue and not seeing the logs does not help.

Anyone knows how I can enable the logging? So when the handler function cannot deserialze the payload in a POST I can see the error in the logs?

This will be appreciated!

Answer 1

Poem uses tracing for logging. You can use any tracing::Subscriber implementation to capture the log output generated by tracing. Probably the most used library for creating a Subscriber is tracing-subscriber.

Here a basic example for creating a Subscriber with tracing-subscriber that logs all log messages created by Poem in a nice format to stdout:

fn main() {
    tracing_subscriber::fmt()
        .with_env_filter("poem=trace")
        .init();

    // here your other code
}

If you want to show all tracing messages generated in all libraries, not just Poem, you can set .with_env_filter("trace"), instead. See this section of how you can configure the EnvFilter. Note that you have to import tracing-subscriber with the env-filter feature flag enabled for this to work.