Collect IBM JVM hang dumps with test reports

[AlexeyKuznetsov-DD]

What Does This Do

• Detect IBM/OpenJ9 from the JVM launcher selected for each Gradle Test task.
• Set IBM_JAVACOREDIR to the same task dump directory collected with test reports.
• Reuse the launcher decision for kill -3 thread dumps and HotSpot-only heap dump suppression.
• Add integration coverage that performs a real IBM javacore capture when an IBM JDK is installed.
• Update the dump investigation guide with the new artifact location.

Motivation

When an IBM test task timed out, kill -3 successfully produced a javacore, but the JVM wrote it outside the module dump directory, typically under /tmp. The CI report collector copies build/dumps, so the diagnostic artifact was unavailable after the job.

The previous /ibm8 executable-path check was also narrower than the Gradle toolchain configuration and could diverge from the JVM selected for the test task.

Additional Notes

Failure evidence from the timeout showed the JVM reporting a successful javacore write under /tmp/javacore...txt, while no javacore appeared in the collected module reports. The selected launcher is now the single source of truth, and IBM_JAVACOREDIR is inherited by the Gradle test worker and its child processes.

Validation:

• ./gradlew -PrunBuildSrcTests=true :buildSrc:test --tests datadog.gradle.plugin.dump.DumpHangedTestIntegrationTest --rerun-tasks --no-build-cache — 8 tests passed, including a real IBM JVM javacore capture.
• ./gradlew :buildSrc:spotlessCheck --no-build-cache

Relevant precedent: #10646 introduced IBM8 thread-dump collection; #12619 established thread-before-heap dump ordering.

OpenJ9 documents IBM_JAVACOREDIR as the Java dump destination: https://eclipse.dev/openj9/docs/env_var/#java-dump-options

Contributor Checklist

• Format the title according to the contribution guidelines
• Assign the type: and (comp: or inst:) labels in addition to any other useful labels
• Avoid using close, fix, or any linking keywords when referencing an issue
  Use solves instead, and assign the PR milestone to the issue
• Update the CODEOWNERS file on source file addition, migration, or deletion
• Update public documentation with any new configuration flags or behaviors
• Once approved, use merge queue to merge the PR

Jira ticket: N/A

[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 2026-09-24T21:19:37.848219Z	fcb6357	Draft marked ready
🔒 Security Review	✅ Completed 2026-09-24T21:17:52.080225Z	fcb6357	Draft marked ready

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[sarahchen6]

LGTM

[chatgpt-codex-connector]

💡 Codex Review

Here are some automated review suggestions for this pull request.

Reviewed commit: fcb6357586

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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	14.79 s	14.64 s	[-0.1%; +2.1%] (no difference)
startup:insecure-bank:tracing:Agent	13.62 s	13.69 s	[-1.3%; +0.4%] (no difference)
startup:petclinic:appsec:Agent	17.05 s	16.98 s	[-0.6%; +1.4%] (no difference)
startup:petclinic:iast:Agent	16.32 s	17.01 s	[-8.2%; +0.2%] (no difference)
startup:petclinic:profiling:Agent	16.70 s	16.83 s	[-2.0%; +0.4%] (no difference)
startup:petclinic:sca:Agent	16.97 s	16.62 s	[+1.1%; +3.1%] (significantly worse)
startup:petclinic:tracing:Agent	16.15 s	16.13 s	[-0.7%; +1.0%] (no difference)

Commit: fcb63575 · CI Pipeline · Benchmarking Platform UI

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

[datadog-official]

An IBM task's dump timer applies its JVM choice to all discovered test processes. This sends SIGQUIT to native children and can stop processes in otherwise healthy parallel tests.

_{Open Bits AI session}

_{🤖 Bits Code Review · Commit fcb6357 · @DataDog review to ask questions}

[AlexeyKuznetsov-DD]

/merge -f --reason "It is a build change, tested in PR, no need to run MQ"

[gh-worker-devflow-routing-ef8351]

View all feedbacks in Devflow UI.

2026-09-25 01:57:11 UTC ℹ️ Start processing command /merge -f --reason "It is a build change, tested in PR, no need to run MQ"

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2026-09-25 01:57:16 UTC ℹ️ MergeQueue: pull request added to the queue

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

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2026-09-25 01:57:26 UTC ℹ️ MergeQueue: This merge request was merged

Warning

This change was merged without running any pre merge CI checks

Reason: It is a build change, tested in PR, no need to run MQ