OTEP 0152 Telemetry Schemas still uses "label" terminology for metrics

[tigrannajaryan]

OTEP 0152 predates renaming of labels to attributes in the spec. Unfortunately the schema file format still uses the term "label" in the metrics section this way:

    metrics:
      changes:
        - rename_labels:
            label_map:
              # map of key/values. The keys are the old label name used
              # in the previous version, the values are the new label name
              # starting from this version.

            apply_to_metrics:
              # Optional. If it is missing the transformation is applied
              # to all metrics. If it is present the transformation is applied
              # only to the metrics with the name that is found in the sequence
              # specified below.

Ideally we don't want the word label in the schema files, instead we want the word attribute to be used instead. Now, the problem is that this is an accepted OTEP and we even published several schema files in the spec. Luckily, none of the publishes schema files have metric transformations.

The question is can we fix this? A couple choices:

1. Keep it as is since we assume the OTEP to be part of the spec and the spec is stable so we can't change it.
2. Consider OTEP to not be final until it is an actual part of the spec repo. We need to merge the OTEP's Schema File proposal in the spec and while doing this we can change all references to "label" by "attribute". If we had published any schemas that used "label" transformation this would be obviously a no go, since we would break schema users. But there is none. There is a very slim chance that someone out there published their own non-Otel schema and used a schema file with a metric label transform in it. I highly doubt it though. We don't have any libraries that allow working with schemas. The very first one I am adding schema file support to is Go SDK (and in fact I only noticed this because I started writing actual code that implements the schema file support).

I would like to know what @open-telemetry/specs-approvers think.

[carlosalberto]

Consider OTEP to not be final until it is an actual part of the spec repo.

+1 to this (in a few cases, when moving it to the Specification we had to amend the initially accepted changes).

The second thing is that although this was published, Metrics still is experimental and as you mentioned, no changes for that portion have been made. I'd rather change it to attributes unless there's a specific compelling reason to not do it.

[iNikem]

Option 2 makes sense to me.

[jsuereth]

I always assumed Option 2 myself, so I vote for that.

[tigrannajaryan]

Discussed in spec meeting, decided:

• OTEPs which are not part of the spec repo are not considered to be final, or be an actual part of stable spec (OTEPs are not labeled "stable" in any way).
• Modify the OTEP, rename label to attribute.
• Merge the OTEP with the spec.