A Prometheus middleware to collect HTTP metrics for Axum applications.

axum-prometheus relies on metrics_exporter_prometheus as a backed to interact with Prometheus.

Metrics

By default three HTTP metrics are tracked

• axum_http_requests_total (labels: endpoint, method): the total number of HTTP requests handled (counter)
• axum_http_requests_duration_seconds (labels: endpoint, method, status): the request duration for all HTTP requests handled (histogram)
• axum_http_requests_pending (labels: endpoint, method): the number of currently in-flight requests (gauge)

Note that in the future request size metric is also planned to be implemented.

Usage

Add axum-prometheus to your Cargo.toml.

not_rust [dependencies] axum-prometheus = "0.1.0"

Then you instantiate the prometheus middleware:

```ignore use std::{net::SocketAddr, time::Duration}; use axum::{routing::get, Router}; use axum_prometheus::PrometheusMetricLayer;

[tokio::main]

async fn main() { let (prometheuslayer, metrichandle) = PrometheusMetricLayer::pair(); let app = Router::new() .route("/fast", get(|| async {})) .route( "/slow", get(|| async { tokio::time::sleep(Duration::fromsecs(1)).await; }), ) .route("/metrics", get(|| async move { metrichandle.render() })) .layer(prometheus_layer);

let addr = SocketAddr::from(([127, 0, 0, 1], 3000));
axum::Server::bind(&addr)
    .serve(app.into_make_service())
    .await
    .unwrap();

} ```

Note that the /metrics endpoint is not automatically exposed, so you need to add that as a route manually. Calling the /metrics endpoint will expose your metrics:

not_rust axum_http_requests_total{method="GET",endpoint="/metrics"} 5 axum_http_requests_pending{method="GET",endpoint="/metrics"} 1 axum_http_requests_duration_seconds_bucket{method="GET",status="200",endpoint="/metrics",le="0.005"} 4 axum_http_requests_duration_seconds_bucket{method="GET",status="200",endpoint="/metrics",le="0.01"} 4 axum_http_requests_duration_seconds_bucket{method="GET",status="200",endpoint="/metrics",le="0.025"} 4 axum_http_requests_duration_seconds_bucket{method="GET",status="200",endpoint="/metrics",le="0.05"} 4 axum_http_requests_duration_seconds_bucket{method="GET",status="200",endpoint="/metrics",le="0.1"} 4 axum_http_requests_duration_seconds_bucket{method="GET",status="200",endpoint="/metrics",le="0.25"} 4 axum_http_requests_duration_seconds_bucket{method="GET",status="200",endpoint="/metrics",le="0.5"} 4 axum_http_requests_duration_seconds_bucket{method="GET",status="200",endpoint="/metrics",le="1"} 4 axum_http_requests_duration_seconds_bucket{method="GET",status="200",endpoint="/metrics",le="2.5"} 4 axum_http_requests_duration_seconds_bucket{method="GET",status="200",endpoint="/metrics",le="5"} 4 axum_http_requests_duration_seconds_bucket{method="GET",status="200",endpoint="/metrics",le="10"} 4 axum_http_requests_duration_seconds_bucket{method="GET",status="200",endpoint="/metrics",le="+Inf"} 4 axum_http_requests_duration_seconds_sum{method="GET",status="200",endpoint="/metrics"} 0.001997171 axum_http_requests_duration_seconds_count{method="GET",status="200",endpoint="/metrics"} 4

This crate is similar to (and takes inspiration from) actix-web-prom and rocket_prometheus, and also builds on top of davidpdrsn's earlier work with LifeCycleHooks in tower-http.