[szegedi]

What does this PR do?:

Adds an OpenTelemetry profiles serializer, built as a ProfileVisitor on the normalizer from #430, and encoding with pprof-format/otel (pprof-format 2.4.0).

Multiple profiles (both time and heap) can be collected into a single ExpoerProfilesServiceRequest sharing the request's dictionary.
Each profile is added through builder.visitor(), so whatever drives the visit needs no knowledge of OTel. serializeTimeProfileOtel() and serializeHeapProfileOtel() are shorthands for a single-profile request.

time.stopAndVisit() and heap.visitProfile() pass the normalized profile to a caller-supplied visitor instead of serializing it as pprof. They're the format-neutral counterparts of time.stop() and heap.profile()

Motivation:

Step 2 of emitting the OpenTelemetry profiles signal from the Node.js profiler: a second encoder that reuses the profile semantics from #430 instead of duplicating them.

Additional notes:

• One OTel profile is emitted per sample type (sample count, wall and CPU time; in-use and allocated objects and space).
• With samplePerContext, the sample count is folded into the wall-time profile, which gets an observation per sampling event. Idle samples, which deliberately have zero wall time (see Preserve idle samples with zero wall time and no CPU time rollup #199), stay as timestamped evidence that sampling happened, and we don't have to have a separate count profile that has to repeat every sample just to carry 1s.
• Labels become interned attributes: strings, integers, or doubles for fractional numbers. An optional extractLink callback can turn labels into a span link; all-zero trace or span IDs are treated as no link.
• Samples with the same stack, attributes and link are merged: timestamped ones accumulate a value and timestamp per observation, others are summed.
• Frames whose source map is declared but missing locally get a datadog.frame.missing_source_map location attribute, and their profiles a datadog.profile.has_missing_source_maps attribute. (pprof carries this as a profile comment, for lack of better solution.) The backend will need to be adjusted to recognize these.

AI generated PR description

Adds an **OpenTelemetry profiles serializer**, built as a `ProfileVisitor` on the format-neutral normalizer from #430, and encoding with `pprof-format/otel` (pprof-format 2.4.0).

• OtelProfilesBuilder (ts/src/otel-serializer.ts) collects any number of normalized profiles, e.g. the time and heap profiles of one collection cycle, into one ExportProfilesServiceRequest. All of them share the request's dictionary, as the OTel format intends. Each profile is added through builder.visitor(), so whatever drives the visit needs no knowledge of OTel. serializeTimeProfileOtel() and serializeHeapProfileOtel() are shorthands for a single-profile request.
• time.stopAndVisit() and heap.visitProfile() pass the normalized profile to a caller-supplied visitor instead of serializing it as pprof. They're the format-neutral counterparts of time.stop() and heap.profile(), and use the same eager stop paths. The lazy, callback-based paths stay opt-in because of the V8 CpuProfile deletion race (Revert lazy profile-tree changes to mitigate CpuProfile::Delete crash #329).

Mapping highlights:

• One OTel profile per sample type (sample count, wall and CPU time; in-use and allocated objects and space).
• With samplePerContext, the sample count is folded into the wall-time profile, which gets an observation per sampling event. Idle samples, which deliberately have zero wall time (see Preserve idle samples with zero wall time and no CPU time rollup #199), thereby stay as timestamped evidence that sampling happened, and no count profile has to repeat every sample just to carry 1s.
• Sample timestamps fall within [time_unix_nano, time_unix_nano + duration_nano), since the time range starts at the start of collection.
• Functions, locations (with columns), stacks, attributes and links are deduplicated across all profiles. Every dictionary table starts with its zero value.
• Labels become interned attributes: strings, integers, or doubles for fractional numbers. An optional extractLink callback can turn labels into a span link; all-zero trace or span IDs are treated as no link.
• Samples with the same stack, attributes and link are merged: timestamped ones accumulate a value and timestamp per observation, others are summed.

Motivation:

Step 2 of emitting the OpenTelemetry profiles signal from the Node.js profiler: a second encoder that reuses the profile semantics from #430 instead of duplicating them.

Additional Notes:

• Stacked on refactor: extract a format-neutral profile normalizer from the pprof serializer #430; only the last two commits are new here.
• The builder isn't exported from the package yet, so that the API can settle first, in particular around how dd-trace-js will drive a collection cycle.
• Frames whose source map is declared but missing locally get a datadog.frame.missing_source_map location attribute, and their profiles a datadog.profile.has_missing_source_maps attribute. pprof carries this as a profile comment, but OTel's pprof.profile.comment is reserved for human-readable text. No semantic convention exists, so these keys are provisional until the Datadog backend confirms them.
• Visitors run synchronously. A visit that throws leaves partial data, so the builder should then be discarded.

How to test the change?:

Unit tests in ts/test/test-otel-serializer.ts cover the mapping, deduplication across profiles, sample merging, links and the missing-source-map attributes, and decode the encoded request to check it round-trips. ts/test/test-time-profiler.ts and ts/test/test-heap-profiler.ts cover stopAndVisit() and visitProfile(), including state after a throwing visitor. npm test.

[github-actions]

Overall package size

Self size: 2.94 MB
Deduped: 4.05 MB
No deduping: 4.05 MB

Dependency sizes

| name | version | self size | total size | |------|---------|-----------|------------| | pprof-format | 2.4.0 | 912.36 kB | 912.36 kB | | source-map | 0.8.0 | 185.66 kB | 185.66 kB | | node-gyp-build | 4.8.4 | 13.86 kB | 13.86 kB |

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