Example for Opentelemetry with Prometheus?

[chikko80]

Hi,
i found this example in the issues: #448
but its really outdated, does anyone know how to setup the PrometheusExporter with opentelemetry like this?

A up-to-date example would be really helpful, can't find anything in the docs for this, i mean there is something with jaeger, but i'd like to use prometheus

[xamgore]

Not Opentelemetry, but gives you a starting point. Just export all the data yourself, it's quite easy.

prometheus-client = "0.22"

async fn main() -> ... {
  let mut registry = <Registry>::default();
  registry.register(...);

  use poem::{Route, Server};
    let app = Route::new().nest("/metrics", PrometheusExporter::new(registry));
    Server::new(poem::listener::TcpListener::bind("0.0.0.0:63012"))
      .run(app)
      .await
}

use poem::http::StatusCode;
use poem::{Endpoint, Request, Response, Result};
use prometheus_client::encoding::text::encode;
use prometheus_client::registry::Registry;

pub struct PrometheusExporter {
  registry: Registry,
}

impl PrometheusExporter {
  pub fn new(registry: Registry) -> Self {
    Self { registry }
  }
}

#[async_trait::async_trait]
impl Endpoint for PrometheusExporter {
  type Output = Response;

  async fn call(&self, _req: Request) -> Result<Self::Output> {
    let mut buffer = String::new();
    encode(&mut buffer, &self.registry)
      .map(|()| {
        Response::builder()
          .content_type("application/openmetrics-text; version=1.0.0; charset=utf-8")
          .body(buffer)
      })
      .map_err(|_err| StatusCode::INTERNAL_SERVER_ERROR.into())
  }
}

[chikko80]

yeah i actually have both running, but didn't have time to prepare some examples for a PR