[reference] reactor-core-3.1 async blind regeneration for #11927

[jordan-wong]

Reference draft for the skill PR #11927. This diff is the output of an automated integration-authoring pass on reactor-core-3.1 (Cat B — context propagation) against the draft skill in that PR. Not intended to be merged as-is — opened so reviewers of #11927 can see concrete output the current skill draft produces.

What this is

Master's reactor-core-3.1 module was deleted, then the automated authoring flow was run against the draft skill in #11927 (the F2/S1/CI-1 rules were in-tree on the target checkout at generation time). This branch is the resulting output.

Base: origin/master
Scope: 25 files, +994/-2741 — only inside dd-java-agent/instrumentation/reactor-core-3.1/ and one entry in metadata/supported-configurations.json.

Generation metrics

• Wall time: ~1.5h
• Cost: ~$13
• Test-fix iterations: 0 (tests passed first try)
• Reviewer iterations: 1 (approved, 0 todos remaining)

Notably smoother than the rxjava-3.0 companion run (~3.5h, $43, 4 test-fix iterations). Possible reasons: fewer types to instrument (Flux + Mono vs 6 rxjava types); or the current skill draft happens to guide reactor-shaped code more directly. Reviewers may find this an interesting data point.

What to look at

• ReactorCoreModule.java: does it extend InstrumenterModule.ContextTracking (correct for Cat B)?
• super(...): single-name pattern per the F2 rule in skill(apm-integrations): additional rules from recent HTTP-category PR reviews #11927
• FluxInstrumentation.java, MonoInstrumentation.java: should contain NO span-lifecycle symbols (startSpan, activateSpan, AgentSpan, AgentScope, Decorator)
• TracingCoreSubscriber.java: the wrapper class that attaches Context.current() at the async boundary
• contextStore() map on the Module
• Sibling AsyncPropagatingDisableInstrumentation in java-concurrent-1.8/ for Reactor's Schedulers.parallel() thread pool

Not for merging

This branch is a reference artifact for the skill PR discussion. The shipping reactor-core-3.1 on master is the authoritative implementation.

🤖 Generated with APM Instrumentation Toolkit

[datadog-datadog-us1-prod]

🎯 Code Coverage (details)
• Patch Coverage: 100.00%
• Overall Coverage: 69.73% (+12.57%)

_{This comment will be updated automatically if new data arrives.
🔗 Commit SHA: dbf3d6b | Docs | Datadog PR Page | Give us feedback!}

[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	13.95 s	13.88 s	[-0.3%; +1.2%] (no difference)
startup:insecure-bank:tracing:Agent	12.94 s	13.00 s	[-1.2%; +0.4%] (no difference)
startup:petclinic:appsec:Agent	16.89 s	16.75 s	[-0.1%; +1.7%] (no difference)
startup:petclinic:iast:Agent	16.83 s	17.03 s	[-1.9%; -0.4%] (maybe better)
startup:petclinic:profiling:Agent	16.79 s	16.23 s	[-1.1%; +8.0%] (no difference)
startup:petclinic:sca:Agent	16.98 s	16.85 s	[-0.3%; +1.9%] (no difference)
startup:petclinic:tracing:Agent	16.10 s	16.16 s	[-1.2%; +0.4%] (no difference)

Commit: dbf3d6b2 · 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.

[jordan-wong]

Rebased 2026-07-14 — branch force-pushed onto current master to fix the shared config-inversion-linter failure (same root cause as PR #11939).

Root cause (not a toolkit bug): the original eval branch inherited a stash-merge revert of #11852 during branch setup. See #11939 comment for the full diagnostic.

Fix: cherry-picked only the in-scope dd-java-agent/instrumentation/reactor-core-3.1/ paths from the original terminal SHA (2e1d2b98d7) onto fresh master (05671ce3b0). All reactor metadata entries were already present on master, so no metadata change is needed.

Result: 24 files changed (all under reactor-core-3.1/), no sibling contamination.

Note for reviewers: the eval reorganized the package layout from datadog.trace.instrumentation.reactor.core (master) to datadog.trace.instrumentation.reactorcore (eval output). This is a Rule #2 (regen-preservation) concern worth flagging — the master module's package layout should typically be preserved verbatim on regen.

Original commit: 2e1d2b98d7 → rebased: dbf3d6b2c7

The 10 CI failures beyond the shared metadata bug are being triaged separately.