WIP: feat(otel): adding support for OpenTelemetry metrics

[rachelyangdog]

What does this PR do?

Motivation

Reviewer's Checklist

• Changed code has unit tests for its functionality at or near 100% coverage.
• System-Tests covering this feature have been added and enabled with the va.b.c-dev version tag.
• There is a benchmark for any new code, or changes to existing code.
• If this interacts with the agent in a new way, a system test has been added.
• New code is free of linting errors. You can check this by running ./scripts/lint.sh locally.
• Add an appropriate team label so this PR gets put in the right place for the release notes.
• Non-trivial go.mod changes, e.g. adding new modules, are reviewed by @DataDog/dd-trace-go-guild.

Unsure? Have a question? Request a review!

[pr-commenter]

Benchmarks

Benchmark execution time: 2025-11-18 22:43:58

Comparing candidate commit ee1546c in PR branch rachel.yang/otel-metrics with baseline commit a1926ab in branch main.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 3 metrics, 0 unstable metrics.

[datadog-official]

⚠️ Tests

⚠️ Warnings

❄️ 2 New flaky tests detected

TestSamplingDecision from github.com/DataDog/dd-trace-go/v2/ddtrace/tracer (Datadog)

Failed

=== RUN   TestSamplingDecision
--- FAIL: TestSamplingDecision (0.06s)

TestSamplingDecision/single_spans_without_max_per_second:rate_0.5 from github.com/DataDog/dd-trace-go/v2/ddtrace/tracer (Datadog)

Failed

=== RUN   TestSamplingDecision/single_spans_without_max_per_second:rate_0.5
    tracer_test.go:731: 
        	Error Trace:	/Users/runner/work/dd-trace-go/dd-trace-go/ddtrace/tracer/tracer_test.go:731
        	Error:      	Max difference between 0.8 and 0.65 allowed is 0.15, but difference was 0.15000000000000002
        	Test:       	TestSamplingDecision/single_spans_without_max_per_second:rate_0.5
    --- FAIL: TestSamplingDecision/single_spans_without_max_per_second:rate_0.5 (0.01s)

ℹ️ Info

🧪 All tests passed

_{This comment will be updated automatically if new data arrives.
🔗 Commit SHA: ee1546c | Docs | Datadog PR Page | Was this helpful? Give us feedback!}