[processor/transform] unable to parse OTTL statement

[nickv2002]

Component(s)

processor/transform

Description

I'm trying to follow the example from here to add metric labels for Prometheus. It suggests using the transform processor like so in order to copy the most common resource attributes into metric labels:

processor:
  transform:
    metric_statements:
      - context: metric
        statements:
        - set(attributes["namespace"], resource.attributes["k8s_namespace_name"])
        - set(attributes["container"], resource.attributes["k8s.container.name"])
        - set(attributes["pod"], resource.attributes["k8s.pod.name"])
        - set(attributes["cluster"], resource.attributes["k8s.cluster.name"])

Given that example I've simplified my collector config down to this simplified version:.

processors:
  transform:
    metric_statements:
      - context: metric
        statements:
          - set(attributes["k8s_namespace_name"], resource.attributes["k8s_namespace_name"])
  resource:
    attributes:
      - key: environment_name
        value: dev
        action: insert
exporters:
  otlphttp:
    endpoint: <Omitted>
service:
  extensions: [health_check]
  pipelines:
    metrics:
      receivers: [otlp]
      processors: [resource, transform, batch]
      exporters: [otlphttp]

Unfortunately, with this configuration, the collector fails to start and complains with the following message:

Error: invalid configuration: processors::transform: unable to parse OTTL statement "set(attributes["k8s_namespace_name"], resource.attributes["k8s_namespace_name"])": error while parsing arguments for call to "set": invalid argument at position 0: invalid metric path expression [{attributes [{0xc002ad2250 }]}]2023/09/20 00:43:53 collector server run finished with error: invalid configuration: processors::transform: unable to parse OTTL statement "set(attributes["k8s_namespace_name"], resource.attributes["k8s_namespace_name"])": error while parsing arguments for call to "set": invalid argument at position 0: invalid metric path expression [{attributes [{0xc002ad2250 }]}]

Collector version

0.85.0

Environment

docker image: otel/opentelemetry-collector-contrib:0.85.0

[github-actions]

Pinging code owners:

• processor/transform: @TylerHelmuth @kentquirk @bogdandrutu @evan-bradley

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

[TylerHelmuth]

The metric context does have have attributes because metrics don't have attributes. Try the datapoint context.

[nickv2002]

The metric context does not have attributes because metrics don't have attributes. Try the datapoint context.

@TylerHelmuth thanks for that tip. I've got it working for several attributes that are now showing up with proper labels in Prometheus/Grafana. Here's an excerpt of my working config (for other's potential ref):

processors:
  transform:
    trace_statements:
      - context: span
        statements:
        - set(resource.attributes["cluster"], "dev")
    metric_statements:
      - context: datapoint
        statements:
        - set(attributes["k8s_namespace"], resource.attributes["k8s.namespace.name"])
        - set(attributes["k8s_container"], resource.attributes["k8s.container.name"])
        - set(attributes["k8s_deployment"], resource.attributes["k8s.deployment.name"])
        - set(attributes["k8s_pod"], resource.attributes["k8s.pod.name"])
        - set(attributes["telemetry_sdk_language"], resource.attributes["telemetry.sdk.language"])
        - set(attributes["cluster"], "dev")

Seems like the documentation should be updated here and here

I will see if I can make a quick PR for that.