Prevent Netty idle timers from retaining request context

[amarziali]

What Does This Do

Prevents Netty’s channel-owned idle timers from capturing the request context active during channel initialization.

IdleStateHandler.initialize() creates recurring timeout tasks. When initialization happens during the first Vert.x request, those tasks can inherit its context even though their lifecycle belongs to the channel
and continues until channel teardown.

The existing async-propagation suppression instrumentation now disables propagation only while these timers are created, restoring the previous state on normal and exceptional exits.

sequenceDiagram
    participant Request as First client request
    participant Handler as Netty IdleStateHandler
    participant Agent as Context instrumentation
    participant Timer as Channel idle timer
    participant Channel

    Request->>Handler: initialize(channel context)
    Handler->>Agent: enter initialize()
    Agent->>Agent: save propagation state
    Agent->>Agent: disable async propagation
    Handler->>Timer: create recurring timeout task
    Note over Timer: Channel-owned task<br/>No request context captured
    Handler-->>Agent: exit initialize()
    Agent->>Agent: restore propagation state
    Handler-->>Request: continue request
    Timer->>Channel: monitor idle state until teardown

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Motivation

The idle timer belongs to the channel rather than to the request that happens to initialize it. Capturing that request’s context retains its continuation beyond request completion and can delay trace publication.

Suppressing capture at the timer-creation boundary preserves normal propagation for Vert.x callbacks, errors, cancellation and request processing.

Additional Notes

Contributor Checklist

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Jira ticket: [PROJ-IDENT]

[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 2026-09-15T10:35:26.093870Z	5a02f2b	PR opened
🔒 Security Review	✅ Completed 2026-09-15T10:36:40.555298Z	5a02f2b	PR opened

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[datadog-datadog-prod-us1-2]

More details

The new matcher limits propagation suppression to IdleStateHandler.initialize(ChannelHandlerContext). The shared advice restores the prior propagation state on normal and exceptional exits.

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[datadog-datadog-prod-us1-2]

🎯 Code Coverage (details)
• Patch Coverage: 100.00%
• Overall Coverage: 68.82% (+9.78%)

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🔗 Commit SHA: 33cc72c | Docs | View more details | 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	14.83 s	14.65 s	[+0.4%; +2.0%] (maybe worse)
startup:insecure-bank:tracing:Agent	13.57 s	13.71 s	[-1.8%; -0.3%] (maybe better)
startup:petclinic:appsec:Agent	17.55 s	17.39 s	[+0.1%; +1.8%] (maybe worse)
startup:petclinic:iast:Agent	17.41 s	17.08 s	[-2.4%; +6.3%] (no difference)
startup:petclinic:profiling:Agent	17.38 s	17.21 s	[-0.1%; +2.1%] (no difference)
startup:petclinic:sca:Agent	17.52 s	16.84 s	[-0.3%; +8.3%] (no difference)
startup:petclinic:tracing:Agent	16.48 s	16.18 s	[-2.5%; +6.1%] (no difference)

Commit: 33cc72c4 · 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.

[ygree]

IDM approved. Side note: AsyncPropagatingDisableInstrumentation targets too many different classes. In my opinion, it should have been split into specialised modules in the first place.

[amarziali]

/merge

[gh-worker-devflow-routing-ef8351]

View all feedbacks in Devflow UI.

2026-09-16 07:54:58 UTC ℹ️ Start processing command /merge

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2026-09-16 07:55:04 UTC ℹ️ MergeQueue: pull request added to the queue

The expected merge time in master is approximately 1h (p90).

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2026-09-16 09:06:27 UTC ℹ️ MergeQueue: This merge request was merged