Crate micromegas_tracing_proc_macros 

Procedural macros for instrumenting Rust functions with tracing spans.

This crate provides #[span_fn] and #[log_fn] attribute macros that automatically inject instrumentation into functions. These macros are the primary way to instrument async code in micromegas.

Quick Start

use micromegas_tracing::prelude::*;

#[span_fn]
async fn fetch_user(id: u64) -> User {
    // This async function is automatically instrumented
    database.get_user(id).await
}

#[span_fn]
fn compute_hash(data: &[u8]) -> Hash {
    // Sync functions work too
    hasher.hash(data)
}

Why use #[span_fn]?

The #[span_fn] macro solves a fundamental challenge in async Rust: tracking execution time across .await points. When an async function awaits, it yields control and may resume on a different thread. #[span_fn] wraps your async code in an InstrumentedFuture that correctly tracks wall-clock time even across these suspension points.

For sync functions, it creates a scope-based span that measures the function’s execution.

Import

These macros are re-exported through the tracing prelude:

use micromegas_tracing::prelude::*;

Attribute Macros

log_fn

Logs function entry with the function name.

span_fn

Instruments a function with automatic span tracing.