Incorrect receiver label in prometheus receiver observability metrics

[olagacek]

Describe the bug

In version 0.20.0 of opentelemetry collector observability metrics coming from prometheus receiver do not contain proper label "receiver" with receiver name - it is set to empty string, instead of "prometheus"

Steps to reproduce

Run Open Telemetry app with prometheus receiver enabled, then scrape localhost:8888 metrics and inspect the returned response.

What did you expect to see?

otelcol_receiver_accepted_metric_points, otelcol_receiver_refused_metric_points metrics having "receiver" label set to "prometheus"

What did you see instead?

otelcol_receiver_accepted_metric_points, otelcol_receiver_refused_metric_points metrics have "receiver" label set to ""

What version did you use?

Version: v0.20.0

What config did you use?

    receivers:
      prometheus:
        use_start_time_metric: true
        config:
          scrape_configs:
            - job_name: "kubelet"
              scrape_interval: 60s
              static_configs:
              - targets: ["127.0.0.1:10255"]
              metric_relabel_configs:
              - source_labels: [ __name__ ]
                regex: "kubelet_docker_operations|kubelet_docker_operations_errors"
                action: keep
    exporters:
      stackdriver:
    service:
      pipelines:
        metrics/prom:
          receivers:
            - prometheus
          exporters:
            - stackdriver

Environment
OS: COS
Compiler(if manually compiled): go 1.14

[yeya24]

I can take this one.

[yeya24]

I think this issue was fixed by open-telemetry/opentelemetry-collector#2680 already

[gillg]

I confirm all metrics I use in otel collector namespace has label like receiver="prometheus" exporter="prometheus"

[odeke-em]

@alolita @bogdandrutu @Aneurysm9 @kirbyquerby could someone please help close this issue? The PR author forgot to attach the "Fixes #NNNN" in their commit message so it didn't auto close, but it was fixed months ago.

[gouthamve]

@dashpole Another issue to close.