[service] Deprecate telemetry.disableHighCardinalityMetrics

[axw]

Description

Deprecate the feature gate now that metric views can be configured.

Link to tracking issue

Fixes #13537

Testing

Verified that the flag is deprecated with otelcorecol featuregate and otelcorecol --feature-gates telemetry.disableHighCardinalityMetrics (the latter leads to an error, as expected for deprecated feature gates.)

Documentation

Added changelog

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.04%. Comparing base (b4a7f4f) to head (e7223b3).
⚠️ Report is 4 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #13538      +/-   ##
==========================================
+ Coverage   92.00%   92.04%   +0.03%     
==========================================
  Files         529      529              
  Lines       31454    31419      -35     
==========================================
- Hits        28939    28919      -20     
+ Misses       1987     1969      -18     
- Partials      528      531       +3     

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[jade-guiton-dd]

So I'm having second thoughts about whether it's a good idea to deprecate this now. Yes, users can now configure metric views that do the same thing as the gate (and at the very least, we'll want to document how).

But because metric views are incompatible with level != detailed, users that were previously using the gate will also have to reproduce all the default level-based views set up in service.go. There was a proposal at one point for a Collector subcommand that lists the metric views for a given level to make this easier, but it hasn't been implemented. So that's a bit of a painful migration path, especially since I suspect users of the feature gate can't easily do without it (it would increase the cardinality of their metrics by a lot).

[jade-guiton-dd]

Looking into it, it might not actually have much of an impact to deprecate this feature flag without an easy migration path, because I think it might have broken a long time ago, and yet nobody complained...

Specifically, it remove the following attributes for gRPC instrumentation metrics:

• net.sock.peer.addr
• net.sock.peer.port
• net.sock.peer.name

And the following from HTTP instrumentation metrics:

• net.host.name
• net.host.port

But:

• this PR renamed those 3 gRPC attributes to follow a newer semantic convention
• this PR made is so the old HTTP attributes are no longer emitted by default
• this PR removes support for emitting the old attributes altogether (done by setting OTEL_SEMCONV_STABILITY_OPT_IN to http/dup)

The first two changes in the Collector have been since v0.128.0, and the third should be in the next go-contrib release.

(Unrelated note: we may want to ask for an authoritative list of metrics and attributes emitted by these instrumentations, having to dig through the code and the Git history every time is exhausting)

[axw]

@jade-guiton-dd thanks for looking into that. I've confirmed through testing with the OTLP receiver that these attributes are not present in any metrics.

I went ahead and removed all references to the feature gate in the code, since deprecating means it cannot be enabled. The view for excluding those attributes is entirely removed, along with references to the attributes in tests.

[jade-guiton-dd]

So after discussing this in the maintainers call, I think the best way to handle this would be to say something to the effect of:

The metrics attributes removed by this feature gate are no longer emitted by the Collector by default, but if needed, you can achieve the same functionality by configuring the following metric views:

service:
  telemetry:
    metrics:
      views:
        - selector:
            meter_name: "go.opentelemetry.io/contrib/instrumentation/google.golang.org/grpc/otelgrpc"
          stream:
            attribute_keys:
              excluded: ["net.sock.peer.addr", "net.sock.peer.port", "net.sock.peer.name"]
        - selector:
            meter_name: "go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp"
          stream:
            attribute_keys:
              excluded: ["net.host.name", "net.host.port"]

Note that this requires setting level: detailed. If you have a strong use case for using views in combination with a different level, please show your interest in this Collector issue.

This gives users who may still be relying on the feature gate something to work with, while allowing us to keep kicking #10769 down the road.

[axw]

Sounds good, thanks - updated.

[jade-guiton-dd]

LGTM