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Reference-chains design and architecture docs by jbachorik · Pull Request #802 · DataDog/java-profiler · GitHub

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Reference-chains design and architecture docs - #802

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Reference-chains design and architecture docs#802
jbachorik wants to merge 2 commits into
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jbachorik commented Sep 17, 2026 •
edited by atlassian Bot
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What does this PR do?:
Adds the reference-chains documentation: the design document, the as-built implementation reference, the signals explainer (search gate, pain budgets, urgency, leak tags), and the collection summary.

Motivation:
Documentation layer for PROF-15341, matching the as-built state of the engine shipped earlier in the stack.

Additional Notes:
Stacked on #801. Docs only — no code.

How to test the change?:
N/A — documentation only.

For Datadog employees:

  • This PR doesn't touch any of that.
  • JIRA: PROF-15341

dd-octo-sts Bot commented Sep 17, 2026 •
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Scan-Build Report

User:runner@runnervmlun5p
Working Directory:/home/runner/work/java-profiler/java-profiler/ddprof-lib/src/test/make
Command Line:make -j4 all
Clang Version:Ubuntu clang version 18.1.3 (1ubuntu1)
Date:Thu Sep 17 20:07:38 2026

Bug Summary

Bug TypeQuantityDisplay?
All Bugs4
C++ move semantics
Use-after-move1
Logic error
Dereference of null pointer1
Result of operation is garbage or undefined1
Unused code
Dead increment1

Reports

Bug Group Bug Type ▾ File Function/Method Line Path Length
Unused codeDead incrementreferenceChains.cppcollectStaticFieldAnchorsForRotation36771
Logic errorDereference of null pointerfaultInjection.cppcrashNow242
Logic errorResult of operation is garbage or undefinedlivenessTracker.cppsecondsToOOM138324
C++ move semanticsUse-after-movereferenceChains.cppbuildCanaryChainEvent608368

datadog-datadog-prod-us1-2 Bot commented Sep 17, 2026 •
edited by datadog-datadog-us1-prod Bot
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✨ Unblock PR with BitsAI

❌ Errors

Your PR has failed checks. Please review the issues below and take necessary action before merging.

🚦 2 Pipeline jobs failed

DataDog/java-profiler | integration-test-x64-musl: [hotspot, 25] — 🔧 Needs a code fix, caused by this PR

View more details · View in GitLab

DataDog/java-profiler | post-pr-comment — 🔧 Needs a code fix, caused by this PR

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🔗 Commit SHA: 19b9d3f | Docs | View more details | Give us feedback!

dd-octo-sts Bot commented Sep 17, 2026 •
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CI Test Results

Run: #35750835257 | Commit: 1e3415c | Duration: 40m 18s (longest job)

❌ 2 of 32 test jobs failed

Status Overview

JDK glibc-aarch64/debug glibc-amd64/debug musl-aarch64/debug musl-amd64/debug
8 - ✅ - -
8-ibm - ✅ - -
8-j9 ✅ ✅ - -
8-librca - - ✅ ✅
8-orcl - ✅ - -
11 - ✅ - -
11-j9 ✅ ✅ - -
11-librca - - ✅ ✅
17 ✅ ✅ - -
17-graal ✅ ✅ - -
17-j9 ✅ ✅ - -
17-librca - - ❌ ✅
21 ✅ ✅ - -
21-graal ✅ ✅ - -
21-librca - - ✅ ❌
25 ✅ ✅ - -
25-graal ✅ ✅ - -
25-librca - - ✅ ✅

Legend: ✅ passed | ❌ failed | ⚪ skipped | 🚫 cancelled

⚠️ Flaky tests — failed, then passed on retry

Test Cells Message
ReferenceChainTestSeamsTest.shouldReconstructChainForDirectlyTaggedRoot__ musl-17-librca-debug-aarch64 Expected pollWatchedTargets() to have queued at least one chain event for the directly-tagged, seeded-representative tar
ReferenceChainTestSeamsTest.shouldSelectSeededKlassAsLeakCandidateOnPositiveSlope__ musl-21-librca-debug-amd64 Expected klass id 987001 to be selected as a leak candidate after a seeded positive-slope population history ==> expecte

These fail the build. Passing on a second run makes a test flaky, not passing. Fix it, or quarantine it against a ticket so the debt is tracked rather than forgotten.

Consider quarantining these — click for ready-made entries

A quarantined test still runs and still reports; its failures just stop
turning CI red. To quarantine one:

  1. Open a PROF ticket for the test, linking the failing job.
  2. Append the line below to ddprof-test/quarantine.txt, replacing
    PROF-XXXXX with the ticket number.
  3. Check the cells and reason columns — the proposal only knows what
    failed in this run, and a narrower cells glob keeps the same test
    gating everywhere it has not misbehaved.

CI fails once review_by passes, so an entry expires instead of piling up.

# test | ticket | added | review_by | cells | reason
com.datadoghq.profiler.referencechains.ReferenceChainTestSeamsTest.shouldReconstructChainForDirectlyTaggedRoot | PROF-XXXXX | 2026-09-22 | 2026-12-21 | musl-17-librca-debug-aarch64 | Expected pollWatchedTargets() to have queued at least one chain event for the directly-tagged, seeded-representative target ==> expected: <true> but was: <false> (seen in: musl-17-librca-debug-aarch64)
com.datadoghq.profiler.referencechains.ReferenceChainTestSeamsTest.shouldSelectSeededKlassAsLeakCandidateOnPositiveSlope | PROF-XXXXX | 2026-09-22 | 2026-12-21 | musl-21-librca-debug-amd64 | Expected klass id 987001 to be selected as a leak candidate after a seeded positive-slope population history ==> expected: <true> but was: <false> (seen in: musl-21-librca-debug-amd64)

Retried 2 of 32 cells.

Failed Jobs

Summary: Total: 32 | Passed: 30 | Failed: 2

Updated: 2026-09-22 16:41:21 UTC

dd-octo-sts Bot commented Sep 17, 2026 •
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❌ 39 passed, 1 failed out of 40 expected configurations

Test Matrix

Platform JDK 8 JDK 11 JDK 17 JDK 21 JDK 25
glibc-x64-hotspot ✅ ✅ ✅ ✅ ✅
glibc-x64-openj9 ✅ ✅ ✅ ✅ ✅
glibc-arm64-hotspot ✅ ✅ ✅ ✅ ✅
glibc-arm64-openj9 ✅ ✅ ✅ ✅ ✅
musl-x64-hotspot ✅ ✅ ✅ ✅ ❌
musl-x64-openj9 ✅ ✅ ✅ ✅ ✅
musl-arm64-hotspot ✅ ✅ ✅ ✅ ✅
musl-arm64-openj9 ✅ ✅ ✅ ✅ ✅

Failure Details

musl-x64-hotspot-jdk25

Profiler-only:

"  Skipped (tracer not expected in this configuration)"
""
"[7/8] Checking for unexpected events..."
"  ✓ No unexpected events found"
""
"[8/8] Scenario-specific validation (ddprof_only)..."
"  Validating profiler-only scenario..."
"  ✓ Profiler-only scenario checks passed"
""
"=== Validation Summary ==="
"ExecutionSample:            0.0 events (datadog.ExecutionSample)"
"Stack traces:               0.0 samples"
"Thread diversity:           0.0 threads"
"Allocation samples:         0.0 events (jdk.ObjectAllocationSample)"
"ThreadAllocationStatistics: 0.0 events"
""
"VALIDATION_FAILED: One or more checks did not pass"

Script executed successfully: 425 commands
VALIDATION_FAILED: Validation checks did not pass

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jbachorik added this pull request to stack #803 September 17, 2026 20:02
jbachorik mentioned this pull request Sep 17, 2026
Merged
2 tasks done
jbachorik force-pushed the jb/rc-8-docs branch 2 times, most recently from 6c5ba81 to 58262d1 Compare September 22, 2026 15:55

dd-octo-sts Bot commented Sep 22, 2026

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Reliability & Chaos Results

❌ 29 failure(s) detected Pipeline: https://gitlab.ddbuild.io/DataDog/java-profiler/-/pipelines/139232204

❌ profiler gmalloc aarch64Xjit 
Could not fetch ddprof 1.51.0-jb_rc-8-docs-SNAPSHOT jar
❌ profiler tcmalloc aarch64Xjit 
Could not fetch ddprof 1.51.0-jb_rc-8-docs-SNAPSHOT jar
❌ profiler tcmalloc amd64Xjit 
Could not fetch ddprof 1.51.0-jb_rc-8-docs-SNAPSHOT jar
❌ profiler tracer gmalloc aarch64Xjit 
Could not fetch ddprof 1.51.0-jb_rc-8-docs-SNAPSHOT jar
❌ profiler tracer jemalloc amd64Xjit 
Could not fetch ddprof 1.51.0-jb_rc-8-docs-SNAPSHOT jar
❌ profiler tracer tcmalloc amd64Xjit 
Could not fetch ddprof 1.51.0-jb_rc-8-docs-SNAPSHOT jar
❌ chaos: profiler gmalloc aarch64 21 0 3 temXchaos 
chaos.jar unavailable
❌ chaos: profiler gmalloc aarch64 25 0 3 temXchaos 
chaos.jar unavailable
❌ chaos: profiler gmalloc amd64 21 0 3 temXchaos 
chaos.jar unavailable
❌ chaos: profiler gmalloc amd64 25 0 3 temXchaos 
ddprof jar unavailable (Maven snapshot download failed)
❌ chaos: profiler jemalloc aarch64 21 0 3 temXchaos 
chaos.jar unavailable
❌ chaos: profiler jemalloc aarch64 25 0 3 temXchaos 
ddprof jar unavailable (Maven snapshot download failed)
❌ chaos: profiler jemalloc amd64 21 0 3 temXchaos 
chaos.jar unavailable
❌ chaos: profiler jemalloc amd64 25 0 3 temXchaos 
chaos.jar unavailable
❌ chaos: profiler tcmalloc aarch64 21 0 3 temXchaos 
chaos.jar unavailable
❌ chaos: profiler tcmalloc aarch64 25 0 3 temXchaos 
chaos.jar unavailable
❌ chaos: profiler tcmalloc amd64 21 0 3 temXchaos 
ddprof jar unavailable (Maven snapshot download failed)
❌ chaos: profiler tcmalloc amd64 25 0 3 temXchaos 
chaos.jar unavailable
❌ chaos: profiler tracer gmalloc aarch64 21 0 3 temXchaos 
chaos.jar unavailable
❌ chaos: profiler tracer gmalloc aarch64 25 0 3 temXchaos 
ddprof jar unavailable (Maven snapshot download failed)
❌ chaos: profiler tracer gmalloc amd64 21 0 3 temXchaos 
chaos.jar unavailable
❌ chaos: profiler tracer gmalloc amd64 25 0 3 temXchaos 
chaos.jar unavailable
❌ chaos: profiler tracer jemalloc aarch64 21 0 3 temXchaos 
ddprof jar unavailable (Maven snapshot download failed)
❌ chaos: profiler tracer jemalloc aarch64 25 0 3 temXchaos 
ddprof jar unavailable (Maven snapshot download failed)
❌ chaos: profiler tracer jemalloc amd64 21 0 3 temXchaos 
chaos.jar unavailable
❌ chaos: profiler tracer jemalloc amd64 25 0 3 temXchaos 
chaos.jar unavailable
❌ chaos: profiler tracer tcmalloc aarch64 21 0 3 temXchaos 
chaos.jar unavailable
❌ chaos: profiler tracer tcmalloc aarch64 25 0 3 temXchaos 
chaos.jar unavailable
❌ chaos: profiler tracer tcmalloc amd64 21 0 3 temXchaos 
chaos.jar unavailable

jbachorik mentioned this pull request Sep 25, 2026
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