Collect thread dumps before heap dumps and start earlier

[AlexeyKuznetsov-DD]

What Does This Do

Start hung-test dump collection 180 seconds before the task timeout instead of 60 seconds. Collect thread dumps for all discovered workers and child processes, followed by the all-JVM thread dump, before starting any heap dumps.

Motivation

Heap-first collection could consume the remaining timeout window before reaching the thread-dump command. Gradle could then terminate the test worker while the collector was still working, leaving no usable thread dump. Collecting stacks first preserves the lightweight diagnostics before expensive heap collection, and starting earlier leaves more time for both.

Additional Notes

Follow-up to #12607, which added command timing and failure diagnostics. Those diagnostics exposed the collection-order problem; that PR did not introduce the heap-first ordering.

In an observed failure, the first worker's heap dump took about 17.5 seconds. The next worker's heap dump took 71.3 seconds, crossing the test task's 20-minute timeout. Its subsequent thread-dump request failed with:

java.io.IOException: Premature EOF
    at sun.tools.attach.HotSpotVirtualMachine.readInt(HotSpotVirtualMachine.java:292)
    at sun.tools.attach.LinuxVirtualMachine.execute(LinuxVirtualMachine.java:200)
    at sun.tools.attach.HotSpotVirtualMachine.executeCommand(HotSpotVirtualMachine.java:261)

The sequence explains the missing thread dump: the request was delayed behind heap collection until task timeout and worker teardown. The triggering task's directory can contain dumps from other active workers, so collecting every worker's stack before any heap dump matters.

Validation: 5 integration tests passed, including the default three-minute offset, thread-before-heap ordering, actual dump creation, directory failure reporting, and heap-command failure reporting.

./gradlew :buildSrc:test -PrunBuildSrcTests --tests datadog.gradle.plugin.dump.DumpHangedTestIntegrationTest

Task timeouts remain enforced. This improves diagnostic collection; it does not address the underlying test slowdown or guarantee that all heap dumps finish before termination.

Contributor Checklist

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[datadog-prod-us1-6]

🎯 Code Coverage (details)
• Patch Coverage: 100.00%
• Overall Coverage: 59.12% (-0.00%)

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[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-09-23T17:46:10.361094Z	0cab7a5	Draft marked ready
🔒 Security Review	✅ Completed 2026-09-23T17:49:04.240956Z	0cab7a5	Draft marked ready

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[dd-octo-sts]

🟢 Java Benchmark SLOs — All performance SLOs passed

Suite	Status
Startup	🟢 pass

SLO thresholds are defined here based on automatically generated metrics. A warning is raised when results are within 5% of the threshold.

PR vs. master results

Scenario	Candidate	master	Δ (95% CI of mean)
startup:insecure-bank:iast:Agent	13.96 s	13.97 s	[-0.9%; +0.7%] (no difference)
startup:insecure-bank:tracing:Agent	12.96 s	13.03 s	[-1.5%; +0.4%] (no difference)
startup:petclinic:appsec:Agent	17.62 s	17.31 s	[+0.8%; +2.7%] (maybe worse)
startup:petclinic:iast:Agent	17.49 s	17.03 s	[-1.8%; +7.3%] (no difference)
startup:petclinic:profiling:Agent	17.44 s	17.30 s	[-0.5%; +2.1%] (no difference)
startup:petclinic:sca:Agent	17.51 s	16.67 s	[+0.8%; +9.4%] (maybe worse)
startup:petclinic:tracing:Agent	16.11 s	16.65 s	[-7.3%; +0.9%] (no difference)

Commit: 0cab7a5a · CI Pipeline · Benchmarking Platform UI

---

Load and DaCapo benchmarks can be triggered manually in the GitLab pipeline. Results will appear in the Benchmarking Platform UI after completion.

[datadog-prod-us1-6]

More details

The collector saves all thread dumps before a heap dump can use the remaining timeout period. The static review found no concrete fault in the new collection order or start time.

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[AlexeyKuznetsov-DD]

/merge -f --reason "Fix for build, tested in PR, no need to run MQ"

[gh-worker-devflow-routing-ef8351]

View all feedbacks in Devflow UI.

2026-09-23 18:16:58 UTC ℹ️ Start processing command /merge -f --reason "Fix for build, tested in PR, no need to run MQ"

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2026-09-23 18:17:02 UTC ℹ️ MergeQueue: pull request added to the queue

The expected merge time in master is approximately 0s (p90).

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2026-09-23 18:17:12 UTC ℹ️ MergeQueue: This merge request was merged

Warning

This change was merged without running any pre merge CI checks

Reason: Fix for build, tested in PR, no need to run MQ