Have profilers emit settings and metrics into `event.json` #6597

szegedi · 2025-10-03T14:47:14Z

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

Additional Notes

Jira: PROF-12666

codecov · 2025-10-03T14:48:03Z

Codecov Report

❌ Patch coverage is 79.68750% with 13 lines in your changes missing coverage. Please review.
✅ Project coverage is 83.30%. Comparing base (2f03518) to head (0f70dda).
⚠️ Report is 1 commits behind head on master.

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   83.54%   83.30%   -0.24%     
==========================================
  Files         504      504              
  Lines       21191    21212      +21     
==========================================
- Hits        17703    17670      -33     
- Misses       3488     3542      +54

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github-actions · 2025-10-03T14:49:05Z

Overall package size

Self size: 12.82 MB
Deduped: 115.43 MB
No deduping: 117.64 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 | 1.14.4 | 123.18 kB | 851.76 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}

pr-commenter · 2025-10-03T14:59:31Z

Benchmarks

Benchmark execution time: 2025-10-15 08:13:28

Comparing candidate commit 0f70dda in PR branch szegedi/profiler-system-info with baseline commit 2f03518 in branch master.

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

packages/dd-trace/src/profiling/profiler.js

nsavoire · 2025-10-08T17:32:57Z

packages/dd-trace/src/profiling/profiler.js

+  // transpose e.g. info.wall.settings to info.settings.wall. That way
+  // we have functional groupings first, then profiler type.
+  infos.settings[type] = info.settings
+  delete info.settings


it seems dangerous to modify the passed object

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

nsavoire · 2025-10-08T17:33:11Z

packages/dd-trace/src/profiling/profiler.js

+  delete info.settings
+  // take over rest of info without transposition
+  if (Object.keys(info).length > 0) {
+    infos[type] = info


No functional grouping here ?

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:

I agree better be consistent with other langages

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 :-)

…t.json

szegedi added the semver-minor label Oct 3, 2025

szegedi force-pushed the szegedi/profiler-system-info branch from 495c192 to d318f4d Compare October 6, 2025 11:59

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szegedi marked this pull request as ready for review October 6, 2025 13:22

szegedi requested a review from a team as a code owner October 6, 2025 13:22

szegedi marked this pull request as draft October 6, 2025 13:49

szegedi marked this pull request as ready for review October 8, 2025 13:36

szegedi requested a review from nsavoire October 8, 2025 13:42

nsavoire reviewed Oct 8, 2025

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nsavoire reviewed Oct 8, 2025

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szegedi mentioned this pull request Oct 9, 2025

chore(deps): bump @datadog/pprof from 5.10.0 to 5.11.0 #6601

Closed

szegedi added 3 commits October 10, 2025 11:09

Alphabetize

07e1860

Allow profilers to contribute values to info.profiler section of even…

1e1e5bd

…t.json

Use new metrics published in pprof-nodejs 5.11.1

dac7b25

szegedi force-pushed the szegedi/profiler-system-info branch from d318f4d to 590378f Compare October 10, 2025 12:20

Move most settings emit to config and profiler

8b179a0

szegedi force-pushed the szegedi/profiler-system-info branch from 590378f to 98b25d8 Compare October 10, 2025 13:08

szegedi added 3 commits October 10, 2025 15:13

Make config field private

cf6cac4

Hardcode the heap profiler stack depth limit

ead76f7

Make space.js fields private

c09e149

szegedi force-pushed the szegedi/profiler-system-info branch from 98b25d8 to c09e149 Compare October 10, 2025 13:13

nsavoire previously approved these changes Oct 13, 2025

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Merge branch 'master' into szegedi/profiler-system-info

0f70dda

szegedi dismissed nsavoire’s stale review via 0f70dda October 15, 2025 08:05

szegedi requested a review from nsavoire October 15, 2025 08:09

nsavoire approved these changes Oct 15, 2025

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szegedi merged commit dafde81 into master Oct 15, 2025
780 of 782 checks passed

szegedi deleted the szegedi/profiler-system-info branch October 15, 2025 09:51

dd-octo-sts bot pushed a commit that referenced this pull request Oct 15, 2025

Have profilers emit settings and metrics into event.json (#6597)

3cb2897

dd-octo-sts bot mentioned this pull request Oct 15, 2025

v5.72.0 proposal #6666

Merged

juan-fernandez pushed a commit that referenced this pull request Oct 15, 2025

Have profilers emit settings and metrics into event.json (#6597)

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What does this PR do?

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Have profilers emit settings and metrics into `event.json` #6597

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