Flow: otelcol.receiver.prometheus component

[rfratto]

Create an OpenTelemetry Collector receiver component called prometheus and expose it as a Flow component called otelcol.receiver.prometheus.

This component would act as a bridge between the otelcol.* component and the prometheus.* components, where it exports a Prometheus storage.Appendable interface for Prometheus components to send metrics to. The Prometheus metrics would then get converted to OpenTelemetry metrics on the fly before being send to the otelcol.* consumers configured with the component.

prometheus.scrape "default" {
  targets = [...]
  send_to = [otelcol.receiver.prometheus.default.receiver] 
}

otelcol.receiver.prometheus "default" {
  output {
    metrics = [otelcol.exporter.otlp.default.input] 
  } 
}

otelcol.exporter.otlp "default" {
  ...
}