Expiring OTel histogram metrics

[dashpole]

As discussed during the community call today, the opentelemetry expiry only handles counters, and not histograms: https://github.com/grafana/beyla/blob/main/pkg/internal/netolly/export/otel/expirer.go#L54. This is because synchronous APIs in OTel do not have delete methods on synchronous instruments: open-telemetry/opentelemetry-specification#3062.

The workaround you can use for OTel is to use the SDK's Producer interface to provide aggregated histogram metric data. Alternatively, you could implement the Prometheus Collector interface (which would also solve this for the Prometheus export, and then use the prometheus bridge (go.opentelemetry.io/contrib/bridges/prometheus, which implements the Producer interface, to plug the histogram into the OTel SDK.

[mariomac]

Addressed in:

• Using experimental OTEL API for removing metrics #937
• OTEL: removing metrics from removed entities #948

Will be public in Beyla 1.7, but you can try it now in the main docker tag.

[dashpole]

looks very cool, and I like that it includes staleness markers.