[receiver/kafka] name label is empty in metrics

[verejoel]

Component(s)

receiver/kafka

What happened?

Description

Metrics emitted from the kafka receiver are emitted with an empty name label. This causes problems in downstream systems that reject these metrics due to the empty label value.

Example from the debug output of our pipeline showing the metrics with empty name labels:

otelcol_kafka_receiver_current_offset{name=,partition=2} 3095809
otelcol_kafka_receiver_current_offset{name=,partition=3} 3277479
otelcol_kafka_receiver_current_offset{name=,partition=0} 25849
otelcol_kafka_receiver_current_offset{name=,partition=1} 25939
otelcol_kafka_receiver_messages{name=,partition=1} 13057
otelcol_kafka_receiver_messages{name=,partition=2} 2384874
otelcol_kafka_receiver_messages{name=,partition=3} 2518850
otelcol_kafka_receiver_messages{name=,partition=0} 12304
otelcol_kafka_receiver_offset_lag{name=,partition=2} 0
otelcol_kafka_receiver_offset_lag{name=,partition=3} 0
otelcol_kafka_receiver_offset_lag{name=,partition=0} 0
otelcol_kafka_receiver_offset_lag{name=,partition=1} 0
otelcol_kafka_receiver_partition_close{name=} 6
otelcol_kafka_receiver_partition_start{name=} 9

These are rejected in our Thanos backend with the following logs:

ts=2025-04-17T21:21:57.778242899Z caller=writer_errors.go:127 level=warn component=receive component=receive-writer tenant=centralinfrastructure msg="Error on series with empty label name or value" numDropped=2
ts=2025-04-17T21:21:57.778323812Z caller=writer_errors.go:127 level=warn component=receive component=receive-writer tenant=centralinfrastructure msg="Error on series with empty label name or value" numDropped=3
ts=2025-04-17T21:22:07.873682383Z caller=writer_errors.go:127 level=warn component=receive component=receive-writer tenant=centralinfrastructure msg="Error on series with empty label name or value" numDropped=2

Steps to Reproduce

This should be a minimal configuration to reproduce:

receivers:
  kafka:
    brokers:
      - ${env:KAFKA_BROKER}
    client_id: ${env:POD_NAME}
    encoding: otlp_proto
    group_id: ${env:KAFKA_CONSUMER_GROUP}
    protocol_version: 3.0.0
    topic: ${env:KAFKA_TOPIC}

  otlp:
    protocols:
      http:
        endpoint: localhost:4318

exporters:
  debug:
    verbosity: normal

service:
  pipelines:
    logs:
      receivers:
        - kafka/test
      exporters:
        - nop

    metrics:
      receivers:
        - otlp
      exporters:
        - debug

  telemetry:
    metrics:
      address: 0.0.0.0:8888
      level: detailed
      readers:
        - periodic:
            exporter:
              otlp:
                endpoint: http://localhost:4318
                protocol: http/protobuf

Expected Result

The name label should be populated with the ID of the receiver.

Actual Result

The name label is empty.

Collector version

v0.124.0

Environment information

Environment

OS: Microsoft Azure Linux 3.0
Kernel version: 6.6.78.1-3.azl3
Container runtime: containerd://2.0.0
Kubernetes: v1.32.3

OpenTelemetry Collector configuration

Log output

Additional context

I think this happens due to the way logsConsumerGroup, metricsConsumerGroup, and tracesConsumerGroup are created.

The ID is present in the struct here, but is never actually set in the function where the consumer group handlers are instantiated (here).

Therefore the id is nil and I guess this leads to the empty name label when c.id.Name() is called here.

[github-actions]

Pinging code owners:

• receiver/kafka: @pavolloffay @MovieStoreGuy @axw

See Adding Labels via Comments if you do not have permissions to add labels yourself.

[verejoel]

Therefore the id is nil

Maybe not nil but it would be an empty component.ID, which I assume would lead to an empty name.