feat(metrics): add support for otlp configurations

[mabdinur]

What does this PR do?

Adds configuration support for OpenTelemetry Metrics in dd-trace-js. Setting DD_METRICS_OTEL_ENABLED=true automatically configures OTLP metrics export with the custom Meter Provider implementation.

Supported Configurations:

• DD_METRICS_OTEL_ENABLED - Enable/disable OpenTelemetry metrics (default: false)
• OTEL_EXPORTER_OTLP_METRICS_ENDPOINT - Metrics endpoint URL (default: http://localhost:4318/v1/metrics)
• OTEL_EXPORTER_OTLP_METRICS_PROTOCOL - Protocol: http/protobuf or http/json (default: http/protobuf)
• OTEL_EXPORTER_OTLP_METRICS_HEADERS - Custom headers for metrics export
• OTEL_EXPORTER_OTLP_METRICS_TIMEOUT - Request timeout in milliseconds (default: 10000)
• OTEL_METRIC_EXPORT_INTERVAL - Export interval in milliseconds (default: 60000)
• Generic OTEL_EXPORTER_OTLP_* variables as fallbacks

Additional Changes:

• Added API documentation in docs/API.md with usage examples for Counter, Histogram, UpDownCounter, and ObservableGauge
• Integrated metrics initialization in tracer proxy
• Added configuration defaults and telemetry tracking
• Created 17 comprehensive configuration tests

Motivation

The custom OpenTelemetry Meter Provider was implemented but not exposed to users. This PR makes the feature production-ready by adding configuration support and onboarding documentation, following the same patterns as OpenTelemetry Logs support.

Plugin Checklist

• Unit tests.
• Integration tests.
• Benchmarks.
• TypeScript definitions.
• TypeScript tests.
• API documentation.
• CI jobs/workflows.

Additional Notes

[github-actions]

Overall package size

Self size: 12.89 MB
Deduped: 115.5 MB
No deduping: 117.71 MB

Dependency sizes

| name | version | self size | total size | |------|---------|-----------|------------| | @datadog/libdatadog | 0.7.0 | 35.02 MB | 35.02 MB | | @datadog/native-appsec | 10.2.1 | 20.64 MB | 20.65 MB | | @datadog/native-iast-taint-tracking | 4.0.0 | 11.72 MB | 11.73 MB | | @datadog/pprof | 5.11.1 | 9.96 MB | 10.34 MB | | @opentelemetry/core | 1.30.1 | 908.66 kB | 7.16 MB | | protobufjs | 7.5.4 | 2.95 MB | 5.73 MB | | @datadog/wasm-js-rewriter | 4.0.1 | 2.85 MB | 3.58 MB | | @opentelemetry/resources | 1.9.1 | 306.54 kB | 1.74 MB | | @datadog/native-metrics | 3.1.1 | 1.02 MB | 1.43 MB | | @opentelemetry/api-logs | 0.205.0 | 201.51 kB | 1.42 MB | | @opentelemetry/api | 1.9.0 | 1.22 MB | 1.22 MB | | jsonpath-plus | 10.3.0 | 617.18 kB | 1.08 MB | | import-in-the-middle | 1.15.0 | 127.66 kB | 856.24 kB | | lru-cache | 10.4.3 | 804.3 kB | 804.3 kB | | @datadog/openfeature-node-server | 0.1.0-preview.10 | 95.11 kB | 401.46 kB | | opentracing | 0.14.7 | 194.81 kB | 194.81 kB | | source-map | 0.7.6 | 185.63 kB | 185.63 kB | | pprof-format | 2.2.1 | 163.06 kB | 163.06 kB | | @datadog/sketches-js | 2.1.1 | 109.9 kB | 109.9 kB | | lodash.sortby | 4.7.0 | 75.76 kB | 75.76 kB | | ignore | 7.0.5 | 63.38 kB | 63.38 kB | | istanbul-lib-coverage | 3.2.2 | 34.37 kB | 34.37 kB | | rfdc | 1.4.1 | 27.15 kB | 27.15 kB | | dc-polyfill | 0.1.10 | 26.73 kB | 26.73 kB | | @isaacs/ttlcache | 1.4.1 | 25.2 kB | 25.2 kB | | tlhunter-sorted-set | 0.1.0 | 24.94 kB | 24.94 kB | | shell-quote | 1.8.3 | 23.74 kB | 23.74 kB | | limiter | 1.1.5 | 23.17 kB | 23.17 kB | | retry | 0.13.1 | 18.85 kB | 18.85 kB | | semifies | 1.0.0 | 15.84 kB | 15.84 kB | | jest-docblock | 29.7.0 | 8.99 kB | 12.76 kB | | crypto-randomuuid | 1.0.0 | 11.18 kB | 11.18 kB | | ttl-set | 1.0.0 | 4.61 kB | 9.69 kB | | mutexify | 1.4.0 | 5.71 kB | 8.74 kB | | path-to-regexp | 0.1.12 | 6.6 kB | 6.6 kB | | module-details-from-path | 1.0.4 | 3.96 kB | 3.96 kB |

_{🤖 This report was automatically generated by heaviest-objects-in-the-universe}

[codecov]

Codecov Report

❌ Patch coverage is 82.35294% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 84.41%. Comparing base (1722dec) to head (c191762).

Files with missing lines	Patch %	Lines
packages/dd-trace/src/config.js	78.57%	3 Missing ⚠️

Additional details and impacted files

@@                        Coverage Diff                        @@
##           munir/otlp-add-meter-provider    #6664      +/-   ##
=================================================================
+ Coverage                          84.40%   84.41%   +0.01%     
=================================================================
  Files                                513      513              
  Lines                              21352    21369      +17     
=================================================================
+ Hits                               18022    18039      +17     
  Misses                              3330     3330              

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[pr-commenter]

Benchmarks

Benchmark execution time: 2025-10-29 17:24:34

Comparing candidate commit c191762 in PR branch munir/add-otel-metrics-configs with baseline commit d69f98a in branch master.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 1601 metrics, 69 unstable metrics.