Add prometheus support

[imraan-go]

Looking at the source code of bunotel, looks like it only support traces. Do you have any plan to support metrics exporting perhaps via opentelemetry? I want to export http metrics along with bun metrics to prometheus.

[vmihailenco]

Yes, bunotel will support metrics. The rough estimation is next week.

[imraan-go]

Any example usage with Treemux router is appreciated. Since metrics collection documentation is missing in the official bun website. @vmihailenco

[vmihailenco]

Well, all you should do is to configure OpenTelemetry to export metrics to Prometheus. I will write an article at blog.uptrace.dev for SEO purposes :), but for now you can try to figure that for yourself - https://github.com/open-telemetry/opentelemetry-go/blob/main/example/prometheus/main.go . The only treemux specific line is http.HandleFunc("/", exporter.ServeHTTP) which can be written as:

-http.HandleFunc("/", exporter.ServeHTTP)
+router.Compat().GET("/", exporter.ServeHTTP)

After that you need to visualize the data somehow. With Uptrace it looks something like this

The histogram accuracy (p50) is really bad, but it will be improved with exponential histograms - github.com/open-telemetry/opentelemetry-go/pull/2261.

[j2gg0s]

I come too late, do you mind i recommand otsql at here .
It supports prometheus & opentelemetry by hook of database/sql .
@vmihailenco

[vmihailenco]

@j2gg0s I've already mentioned it here and will add it to the bun readme as well.

I still hope to add instructions for OpenTelemetry and Prometheus, just was busy working on OpenTelemetry mentrics documentation...

[vmihailenco]

I've added links at bun, but the main doc is here.