otelconf: fix Prometheus reader converting dot-style labels to underscores

[dmitryax]

When both without_type_suffix and without_units are set (which is the default config for the OTel Collector), prometheusReaderOpts was selecting UnderscoreEscapingWithoutSuffixes as the translation strategy. This strategy sets LabelNamer{UTF8Allowed: false}, converting OTel dot-style label names (e.g. service.name) to underscore-style (service_name) in target_info and on all metric datapoints.

Fix by using NoTranslation instead, which preserves dot-style label names (ShouldEscape()=false) and suppresses metric name suffixes (ShouldAddSuffixes()=false).

The restored behavior is close to what we had before #8595.

Related issue: open-telemetry/opentelemetry-collector-contrib#47011

I manually tested it and it solves the issue above for the collector

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.1%. Comparing base (529b99f) to head (a395b37).
⚠️ Report is 68 commits behind head on main.

Additional details and impacted files

@@          Coverage Diff          @@
##            main   #8696   +/-   ##
=====================================
  Coverage   82.1%   82.1%           
=====================================
  Files        183     183           
  Lines      13790   13790           
=====================================
  Hits       11332   11332           
  Misses      2054    2054           
  Partials     404     404           

Files with missing lines	Coverage Δ
otelconf/v0.3.0/metric.go	89.7% <100.0%> (ø)

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[XSAM]

Should we verify the body contains target_info and not contains the target.info? This prevents MetricNamer accidentally takes TranslationStrategyOption.NoTranslation seriously in the future.

[dmathieu]

See collector upgrade slack thread: https://cloud-native.slack.com/archives/C02JJK840SH/p1773874400856229

I agree with @codeboten's comments on that thread. When setting up the prometheus exporter, we should follow the prometheus conventions, not enforce the OTel ones.

[MrAlias]

cc @dashpole

[dashpole]

Is the collector able to use NoTranslation if it wants this behavior? Escaping to underscores is the correct default behavior according to the prometheus sdk exporter spec.

[dmitryax]

This is just an attempt to address a regression on the collector side appeared in 0.148.0 release when instead of getting the following resource for internal collector metrics

Resource attributes:
     -> service.name: Str(otelcontribcol)
     -> service.instance.id: Str(35ccf925-339a-47e6-a3f8-043013267950)
     -> server.port: Str(8888)
     -> url.scheme: Str(http)
     -> service.version: Str(0.147.0-dev)

we started getting

Resource attributes:
     -> service.name: Str(otel-collector)
     -> service.instance.id: Str(0.0.0.0:8888)
     -> server.port: Str(8888)
     -> url.scheme: Str(http)
     -> service_instance_id: Str(09da6493-2d67-4201-b962-8396ba5c5618)
     -> service_name: Str(otelcontribcol)
     -> service_version: Str(0.148.0-dev)

with the collector's default configuration.

According the @dmathieu this can be resolved by moving collector go sdk config to 1.0. If that better way, I'm happy to close this PR.

For now I've marked this issue as a collector release blocker

[codeboten]

Since setting the translation strategy via the old configuration options was causing problems for the one known use case of the package, i'm in favour of this fix until the collector can move to 1.0.

Please add the same fix to 0.2.0 for consistency

[codeboten]

Suggested change

	- Fix `go.opentelemetry.io/contrib/otelconf` Prometheus reader converting OTel dot-style label names (e.g. `service.name`) to underscore-style (`service_name`) in `target_info` when both `without_type_suffix` and `without_units` are set. Use `NoTranslation` instead of `UnderscoreEscapingWithoutSuffixes` to preserve dot-style label names while still suppressing metric name suffixes. (#PLACEHOLDER)
	- Fix `go.opentelemetry.io/contrib/otelconf` Prometheus reader converting OTel dot-style label names (e.g. `service.name`) to underscore-style (`service_name`) in `target_info` when both `without_type_suffix` and `without_units` are set. Use `NoTranslation` instead of `UnderscoreEscapingWithoutSuffixes` to preserve dot-style label names while still suppressing metric name suffixes. (#8696 )

[dmitryax]

Replaced by #8763

[codeboten]

Thanks @dmitryax for the initial pr, apologies for overriding your pr here, was trying to get this merged as soon as possible :)