Have profilers emit settings and metrics into event.json

[szegedi]

What does this PR do?

Profiler uploads contain a file event.json that has a section for system info. The contents of system info are often language specific. So far we had the agent exporter set some system-specific values in it, but we want to generalize it a bit so that both the profiler config as well as individual profiler facets (wall, heap, events) can contribute values there as well. The config contributes its own settings, while the facets contribute either metrics or computed settings.

In this iteration, the wall profiler contributes metrics for tracking the usage of async sample contexts when using AsyncContextFrame on Node.js 24+.

Additionally, the wall profiler now emits telemetry about the async sample contexts as well. This telemetry is defined in https://github.com/DataDog/dd-go/pull/190144

The PR contains commits that also make fields private in various touched classes. I also noticed while examining candidate for emitted settings that the stack depth in space.js will always be the hardcoded 64 as there's no external way to set it. Hardcoding it allows us to presume the value in the backend, which has some special handling for truncated frames.

Motivation

Having more information in uploaded profiles about the system configuration + having insight into the use of async sample contexts.

Plugin Checklist

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

Additional Notes

Jira: PROF-12666

[codecov]

Codecov Report

❌ Patch coverage is 79.68750% with 13 lines in your changes missing coverage. Please review.
✅ Project coverage is 83.55%. Comparing base (ab33cb0) to head (c09e149).

Files with missing lines	Patch %	Lines
packages/dd-trace/src/profiling/profilers/wall.js	28.57%	5 Missing ⚠️
packages/dd-trace/src/profiling/profilers/space.js	80.95%	4 Missing ⚠️
packages/dd-trace/src/profiling/profiler.js	88.46%	3 Missing ⚠️
...ackages/dd-trace/src/profiling/profilers/events.js	83.33%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #6597      +/-   ##
==========================================
- Coverage   83.80%   83.55%   -0.25%     
==========================================
  Files         490      490              
  Lines       20653    20674      +21     
==========================================
- Hits        17308    17275      -33     
- Misses       3345     3399      +54     

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[github-actions]

Overall package size

Self size: 12.65 MB
Deduped: 112.91 MB
No deduping: 113.3 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 | | @datadog/native-metrics | 3.1.1 | 1.02 MB | 1.43 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 | 1.14.4 | 123.18 kB | 851.76 kB | | lru-cache | 10.4.3 | 804.3 kB | 804.3 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}

[pr-commenter]

Benchmarks

Benchmark execution time: 2025-10-10 13:26:28

Comparing candidate commit c09e149 in PR branch szegedi/profiler-system-info with baseline commit ab33cb0 in branch master.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 1606 metrics, 64 unstable metrics.

[datadog-datadog-prod-us1]

✅ Tests

🎉 All green!

❄️ No new flaky tests detected
🧪 All tests passed

_{This comment will be updated automatically if new data arrives.
🔗 Commit SHA: c09e149 | Docs | Was this helpful? Give us feedback!}

[nsavoire]

it seems dangerous to modify the passed object

[szegedi]

Fair. It happens infrequently enough that it's not necessary to optimize for this.

[nsavoire]

No functional grouping here ?

[szegedi]

I thought not, the rest are typically metrics, so they'll end up as
wall.totalAsyncContextCount. Of course, we could embed this into another level, e.g. metrics so then it'd become wall.metrics.totalAsyncContextCount and we could then transpose that to metrics.wall.totalAsyncContextCount. FWIW, we don't even need to do the whole transposition, it just adds complexity; I originally wanted a top-level settings key because that's how e.g. Ruby does it, so I wanted to keep it a bit consistent with it:

[nsavoire]

I agree better be consistent with other langages

[szegedi]

I actually now reworked it so that settings are constructed by config.js and embedded in system info by top-level profiler inprofiler.js and very little is left in individual profiler facets, just computed settings and metrics, and for those I don't bother with transposition anymore. I think it's much better this way, but I needed you asking to nudge me into rethinking it :-)