Logging

Logs provide immediate feedback on the operation of your applications. Logs let you capture events that are significant in your application's domain, like orders being placed. Logs also help you debug issues in live applications, like lost order confirmation emails.

The emit! macro

In emit, logs are events; a combination of timestamp, message template, and properties. When something significant happens in the execution of your applications, you can log an event for it:

#![allow(unused)]
fn main() {
extern crate emit;
fn confirm_email(user: &str, email: &str) {
    emit::emit!("{user} confirmed {email}");
}
}

Event {
    mdl: "my_app",
    tpl: "{user} confirmed {email}",
    extent: Some(
        "2024-10-01T22:21:08.136228524Z",
    ),
    props: {
        "email": "user-123@example.com",
        "user": "user-123",
    },
}

emit also defines macros for emitting events at different levels for filtering:

• debug! for events supporting live debugging.
• info! for most informative events.
• warn! for errors that didn't cause the calling operation to fail.
• error! for errors that caused the calling operation to fail.

See Levels for details.

An example log produced by emit rendered to the console