[POC] Make scope attributes as identifying for Tracer, Meter, Logger

[pellared]

trafficstars

Spike for https://github.com/open-telemetry/opentelemetry-specification/pull/4161 (and https://github.com/open-telemetry/opentelemetry-go/issues/3368)

API changes:

• Add Attributes attribute.Set field to instrumentation.Scope, logtest.ScopeRecords

Behavioral changes:

• The Tracer, Meter, Logger returned by the providers now handle scope attribute; the value is assigned by the SDK and it is seen as one of the identifying fields
• OTLP ans STDOUT exporters set the instrumentation scope attributes

Remarks:

Zipkin exporter DOES NOT set the instrumentation scope attributes as it is not required by the spec: https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/trace/sdk_exporters/zipkin.md. This may be a bug or missing feature in the spec.

Prometheus exporter is REQUIRED to set the instrumentation scope attributes on the otel_scope_info metric: https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/metrics/sdk_exporters/prometheus.md and https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/compatibility/prometheus_and_openmetrics.md#instrumentation-scope-1:

Scope attributes MUST also be added as labels following the rules described in the Metric Attributes section below.

I have not implemented this this as I do not feel it is needed for this PoC. It would probably require updating the createScopeInfoMetric implementation: https://github.com/open-telemetry/opentelemetry-go/blob/97ee172f1f9af2abb8db7f17567ecdf23779103d/exporters/prometheus/exporter.go#L353-L357

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 84.6%. Comparing base (078b2dd) to head (ea5fbd9). Report is 243 commits behind head on main.

Additional details and impacted files

@@          Coverage Diff          @@
##            main   #5806   +/-   ##
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  Coverage   84.6%   84.6%           
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  Files        272     272           
  Lines      22839   22858   +19     
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+ Hits       19325   19344   +19     
  Misses      3170    3170           
  Partials     344     344           

see 13 files with indirect coverage changes

[pellared]

@open-telemetry/go-maintainers, can you make a rough review if it looks like a good way to implement https://github.com/open-telemetry/opentelemetry-specification/pull/4161? This PR is done in a PoC manner and it lacks unit tests - I just added few more assertions to validate the implementation.

I plan to make https://github.com/open-telemetry/opentelemetry-specification/pull/4161 as "ready to merge" tomorrow.

[MrAlias]

This looks in line with our prior attempt: https://github.com/open-telemetry/opentelemetry-go/pull/3131

[dashpole]

Looks reasonable to me. Prometheus exporter is only supposed to add those attributes to the otel_scope_info metric, btw.

[pellared]

Prometheus exporter is only supposed to add those attributes to the otel_scope_info metric, btw.

I think this is what I described. If not then please update my description 😉

[dmathieu]

This look nice. Does it impact the benchmarks for tracer/meter/logger retrieval?

[pellared]

This look nice. Does it impact the benchmarks for tracer/meter/logger retrieval?

It does (because there is a bigger memory footprint) but IMO not significantly. E.g.

pkg: go.opentelemetry.io/otel/sdk/log
cpu: Intel(R) Core(TM) i9-10885H CPU @ 2.40GHz
                        │   old.txt    │               new.txt               │
                        │    sec/op    │   sec/op     vs base                │
LoggerProviderLogger-16   639.8n ± 14%   738.4n ± 9%  +15.42% (p=0.009 n=10)

                        │   old.txt   │               new.txt               │
                        │    B/op     │    B/op      vs base                │
LoggerProviderLogger-16   349.0 ± 19%   463.0 ± 26%  +32.66% (p=0.009 n=10)

                        │  old.txt   │            new.txt             │
                        │ allocs/op  │ allocs/op   vs base            │
LoggerProviderLogger-16   1.000 ± 0%   1.000 ± 0%  ~ (p=1.000 n=10) ¹

[pellared]

Looks reasonable to me. Prometheus exporter is only supposed to add those attributes to the otel_scope_info metric, btw.

@dashpole, PTAL ea10e400c