Prometheus middleware for actix-web

Prometheus instrumentation for actix-web. This middleware is heavily influenced by the work in sd2k/rocket_prometheus. We track the same default metrics and allow for adding user defined metrics.

By default two metrics are tracked (this assumes the namespace actix_web_prom):

• actix_web_prom_http_requests_total (labels: endpoint, method, status): the total number of HTTP requests handled by the actix HttpServer.

• actix_web_prom_http_requests_duration_seconds (labels: endpoint, method, status): the request duration for all HTTP requests handled by the actix HttpServer.

Usage

First add actix-web-prom to your Cargo.toml:

toml [dependencies] actix-web-prom = "0.2"

You then instantiate the prometheus middleware and pass it to .wrap():

```rust use std::collections::HashMap;

use actixweb::{web, App, HttpResponse, HttpServer}; use actixweb_prom::PrometheusMetrics;

fn health() -> HttpResponse { HttpResponse::Ok().finish() }

[actix_rt::main]

async fn main() -> std::io::Result<()> { let mut labels = HashMap::new(); labels.insert("label1".tostring(), "value1".tostring()); let prometheus = PrometheusMetrics::new("api", Some("/metrics"), Some(labels)); HttpServer::new(move || { App::new() .wrap(prometheus.clone()) .service(web::resource("/health").to(health)) }) .bind("127.0.0.1:8080")? .run() .await } ```

Using the above as an example, a few things are worth mentioning: - api is the metrics namespace - /metrics will be auto exposed (GET requests only) - Some(labels) is used to add fixed labels to the metrics; None can be passed instead if no additional labels are necessary.

A call to the /metrics endpoint will expose your metrics:

```shell $ curl http://localhost:8080/metrics

HELP apihttprequestsdurationseconds HTTP request duration in seconds for all requests

TYPE apihttprequestsdurationseconds histogram

apihttprequestsdurationsecondsbucket{endpoint="/metrics",label1="value1",method="GET",status="200",le="0.005"} 1 apihttprequestsdurationsecondsbucket{endpoint="/metrics",label1="value1",method="GET",status="200",le="0.01"} 1 apihttprequestsdurationsecondsbucket{endpoint="/metrics",label1="value1",method="GET",status="200",le="0.025"} 1 apihttprequestsdurationsecondsbucket{endpoint="/metrics",label1="value1",method="GET",status="200",le="0.05"} 1 apihttprequestsdurationsecondsbucket{endpoint="/metrics",label1="value1",method="GET",status="200",le="0.1"} 1 apihttprequestsdurationsecondsbucket{endpoint="/metrics",label1="value1",method="GET",status="200",le="0.25"} 1 apihttprequestsdurationsecondsbucket{endpoint="/metrics",label1="value1",method="GET",status="200",le="0.5"} 1 apihttprequestsdurationsecondsbucket{endpoint="/metrics",label1="value1",method="GET",status="200",le="1"} 1 apihttprequestsdurationsecondsbucket{endpoint="/metrics",label1="value1",method="GET",status="200",le="2.5"} 1 apihttprequestsdurationsecondsbucket{endpoint="/metrics",label1="value1",method="GET",status="200",le="5"} 1 apihttprequestsdurationsecondsbucket{endpoint="/metrics",label1="value1",method="GET",status="200",le="10"} 1 apihttprequestsdurationsecondsbucket{endpoint="/metrics",label1="value1",method="GET",status="200",le="+Inf"} 1 apihttprequestsdurationsecondssum{endpoint="/metrics",label1="value1",method="GET",status="200"} 0.00003 apihttprequestsdurationsecondscount{endpoint="/metrics",label1="value1",method="GET",status="200"} 1

HELP apihttprequests_total Total number of HTTP requests

TYPE apihttprequests_total counter

apihttprequests_total{endpoint="/metrics",label1="value1",method="GET",status="200"} 1 ```

Custom metrics

You instantiate PrometheusMetrics and then use its .registry to register your custom metric (in this case, we use a IntCounterVec.

Then you can pass this counter through .data() to have it available within the resource responder.

```rust use actixweb::{web, App, HttpResponse, HttpServer}; use actixweb_prom::PrometheusMetrics; use prometheus::{opts, IntCounterVec};

fn health(counter: web::Data) -> HttpResponse { counter.withlabelvalues(&["endpoint", "method", "status"]).inc(); HttpResponse::Ok().finish() }

[actix_rt::main]

async fn main() -> std::io::Result<()> { let prometheus = PrometheusMetrics::new("api", Some("/metrics"), None);

let counter_opts = opts!("counter", "some random counter").namespace("api");
let counter = IntCounterVec::new(counter_opts, &["endpoint", "method", "status"]).unwrap();
prometheus
    .registry
    .register(Box::new(counter.clone()))
    .unwrap();

HttpServer::new(move || {
    App::new()
        .wrap(prometheus.clone())
        .data(counter.clone())
        .service(web::resource("/health").to(health))
})
.bind("127.0.0.1:8080")?
.run()
.await

} ```