opentelemetry-collector-contrib: Prometheus Receiver - Some counter metrics dropped for unknown reason

Describe the bug Analyzing an opentelemetry collector setup and trying to create dashboards with collected metrics, I discovered some droped metrics for an unknown reason. I have a bunch of “dropped” metrics without any logs or traces. Eventualy, I have some logs info internal/metrics_adjuster.go:357 Adjust - skipping unexpected point {"kind": "receiver", "name": "prometheus", "type": "UNSPECIFIED"} So they seems dropped due to an unspecified type. I added some logs on metricFamily.go to vizualize their metada, and they are empty.

As exemple this list completly disapear between the receiver and the exporter :

otel-collector    | cortex_deprecated_flags_inuse_total {Metric: Type: Help: Unit:}
otel-collector    | cortex_experimental_features_in_use_total {Metric: Type: Help: Unit:}
otel-collector    | go_memstats_alloc_bytes_total {Metric: Type: Help: Unit:}
otel-collector    | go_memstats_frees_total {Metric: Type: Help: Unit:}
otel-collector    | go_memstats_lookups_total {Metric: Type: Help: Unit:}
otel-collector    | go_memstats_mallocs_total {Metric: Type: Help: Unit:}
otel-collector    | grafana_api_admin_user_created_total {Metric: Type: Help: Unit:}
otel-collector    | grafana_api_dashboard_snapshot_create_total {Metric: Type: Help: Unit:}
otel-collector    | grafana_api_dashboard_snapshot_external_total {Metric: Type: Help: Unit:}
otel-collector    | grafana_api_dashboard_snapshot_get_total {Metric: Type: Help: Unit:}
otel-collector    | grafana_api_login_oauth_total {Metric: Type: Help: Unit:}
otel-collector    | grafana_api_login_post_total {Metric: Type: Help: Unit:}
otel-collector    | grafana_api_login_saml_total {Metric: Type: Help: Unit:}
otel-collector    | grafana_api_models_dashboard_insert_total {Metric: Type: Help: Unit:}
otel-collector    | grafana_api_org_create_total {Metric: Type: Help: Unit:}
otel-collector    | grafana_api_response_status_total {Metric: Type: Help: Unit:}
otel-collector    | grafana_api_user_signup_completed_total {Metric: Type: Help: Unit:}
otel-collector    | grafana_api_user_signup_invite_total {Metric: Type: Help: Unit:}
otel-collector    | grafana_api_user_signup_started_total {Metric: Type: Help: Unit:}
otel-collector    | grafana_aws_cloudwatch_get_metric_data_total {Metric: Type: Help: Unit:}
otel-collector    | grafana_aws_cloudwatch_get_metric_statistics_total {Metric: Type: Help: Unit:}
otel-collector    | grafana_aws_cloudwatch_list_metrics_total {Metric: Type: Help: Unit:}
otel-collector    | grafana_datasource_request_total {Metric: Type: Help: Unit:}
otel-collector    | grafana_db_datasource_query_by_id_total {Metric: Type: Help: Unit:}
otel-collector    | grafana_emails_sent_total {Metric: Type: Help: Unit:}
otel-collector    | grafana_instance_start_total {Metric: Type: Help: Unit:}
otel-collector    | grafana_page_response_status_total {Metric: Type: Help: Unit:}
otel-collector    | grafana_proxy_response_status_total {Metric: Type: Help: Unit:}
otel-collector    | http_request_total {Metric: Type: Help: Unit:}
otel-collector    | loki_logql_querystats_duplicates_total {Metric: Type: Help: Unit:}
otel-collector    | loki_logql_querystats_ingester_sent_lines_total {Metric: Type: Help: Unit:}
otel-collector    | process_cpu_seconds_total {Metric: Type: Help: Unit:}

I had to put custom logs to understand, and the seems dropped because the Type is unspecified and they have no metadata from metricFamily.go

For an unknown reason some other metrics ending with _total are working like :

node_cpu_seconds_total{cpu="0",mode="idle"}

Steps to reproduce I don’t know exactly… Try to scrap a grafana API on http://grafana:3000/metrics

What did you expect to see? Metrics should be kept internaly, then visible at the exporter side.

What did you see instead? No metrics at the exporter side, and probably dropped on metrics_adjuster.go (a log with metric name is definitely missing here)

What version did you use? 0.25