Metric metadata isn't printed during debug verbosity: detailed

[agardnerIT]

Component(s)

No response

What happened?

transform:
    error_mode: ignore
    metric_statements:
      - context: metric
        statements:
          - set(metric.metadata["user_id"], "555") where metric.name == "order_total"

...

exporters:
  debug:
    verbosity: detailed

Shows

Metric #0
Descriptor:
     -> Name: order_total
     -> Description: 
     -> Unit: gauge
     -> DataType: Gauge
NumberDataPoints #0
StartTimestamp: 1970-01-01 00:00:00 +0000 UTC
Timestamp: 2026-03-02 00:05:09.417257 +0000 UTC
Value: 18.000000
        {"resource": {"service.instance.id": "12341234-abcd-1234-1234-1234abcd1234", "service.name": "otelcol-contrib", "service.version": "0.145.0"}, "otelcol.component.id": "debug", "otelcol.component.kind": "exporter", "otelcol.signal": "metrics"}

Note: This is actually otelcol-contrib v0.146.0 but see open-telemetry/opentelemetry-collector-releases#1394

Collector version

v0.146.0

Environment information

Environment

OS: (e.g., "Ubuntu 20.04")
Compiler(if manually compiled): (e.g., "go 14.2")

OpenTelemetry Collector configuration

Log output

Additional context

No response

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[57Ajay]

Hey @agardnerIT @TylerHelmuth - I'd like to work on this if it's available. Happy to investigate and propose a fix!

[57Ajay]

I have successfully reproduced this issue. It appears the debug exporter (in the core collector) does not currently serialize the Metadata field in logMetricDescriptor.
Since the debug exporter lives in the core repository, I will open an tracking issue and a PR in open-telemetry/opentelemetry-collector to resolve this. I'll link back here once the PR is ready.

[andrzej-stencel]

Thanks @agardnerIT for raising this. And thanks @57Ajay for correctly mentioning that this is on Debug exporter. Closing this in favor of open-telemetry/opentelemetry-collector#14667.