[Prometheus Exporter] Unable to disable otel_scope_name attribute

[timwoj]

According to the spec for the Prometheus exporter:

Prometheus exporters SHOULD provide a configuration option to disable the otel_scope_info metric and otel_scope_ labels.

I can't find any way to actually disable these. The prometheus exporter would disable them assuming the strings passed in via the scope data are empty. The data in the InstrumentationScope that gets passed into the exporter comes from agruments passed to GetMeter(). Passing a blank string for library_name would ostensibly disable it based on the code in the exporter, but passing a blank there results in an error:

[Warning] File: <>/auxil/opentelemetry-cpp/sdk/src/metrics/meter_provider.cc:54 [MeterProvider::GetMeter] Library name is empty.

[marcalff]

See PrometheusExporterOptions::populate_target_info.

This can be set programatically.

The missing part is to expose an environment variable so that this property can also be set from the execution environment.

[timwoj]

See PrometheusExporterOptions::populate_target_info.

This can be set programatically.

I set this to false and otel_scope_name is still part of every instrument in the output. It looks like all this setting does is remove the target_info instrument from being reported.

[marcalff]

Indeed, populate_target_info is for something different, sorry about the confusion.

So we need a new exporter option attributes, and the environment variable that goes with it, this is a valid issue.

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[marcalff]

Reopen.

This collides with the following spec PR, which defines the option and environment variable to use:

• add optional otel_scope_info configuration for prometheus exporter opentelemetry-specification#3796

[marcalff]

On hold, waiting for the spec PR to be approved and merged:

• add optional otel_scope_info configuration for prometheus exporter opentelemetry-specification#3796

options and environment variables to be renamed after that.

Important: to fix before the next opentelemetry-cpp release is shipped, to avoid un necessary changes to users.

[timwoj]

Looks like the spec PR was merged. I'll try to get a PR that renames it done this week.

[timwoj]

Looks like the spec PR was merged. I'll try to get a PR that renames it done this week.

Should I rename all of the populate_otel_scope variables in the original PR, or just the environment variable? I'm only asking because of the clash with the naming of populate__target_info.

[timwoj]

Ping on the above question, which probably got lost in the holidays.

[marcalff]

@timwoj

Everything related to populate_otel_scope is not published yet in opentelemetry-cpp, because it was merged after the last release 1.13.0.

So, please rename C++ member names, parameter names, etc, and the environment variable name.

Once this renaming is done, we can then ship a clean 1.14.0.

Not sure what conflict with populate_target_info this can cause, if any.

Given that the spec itself is in experimental status for this area, renaming can be done around populate_target_info if necessary, we just have to document this as a breaking change in the changelog (breaking changes in the SDK are acceptable).