Prevent Pekko stream lifecycle context retention

[amarziali]

What Does This Do

Pekko HTTP registers a shutdown callback from StreamUtils.preStart(). When this happens during a request, Scala’s callback instrumentation captures the active context and retains it until the stream shuts down.

This change temporarily disables async propagation only while that callback is registered. It uses the existing context-tracking instrumentation, without creating a no-op span or affecting the active request
context.

  flowchart LR
      A[Active request context] --> B[StreamUtils.preStart]
      B -->|async propagation disabled| C[Register shutdown callback]
      C --> D[Restore async propagation]
      A -. not captured .-> C

Loading

Why?

The shutdown callback belongs to the stream lifecycle, not to the request that happened to initialize it. Propagating the request context there creates a continuation that can remain unresolved until server
shutdown.

The matcher is limited to the exact Pekko stream-stage type and its preStart() method.

Akka

Akka has similar code, but its equivalent IAST scenario does not retain a continuation. Tests passed with Akka HTTP 10.1, 10.2, and the latest supported dependencies, so no speculative Akka suppression was added.

Motivation

Additional Notes

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: [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 2026-09-11T16:15:18.677626Z	9c27dfe	PR opened
🔒 Security Review	✅ Completed 2026-09-11T16:16:48.858798Z	9c27dfe	PR opened

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review" or "@codex security review".

Codex reacts with 👀 while any review is running, comments if it has suggestions, and reacts with 👍 once all reviews finish with no findings.

[datadog-prod-us1-6]

More details

The exact Pekko stream-stage matcher applies existing async propagation control only during preStart. The advice restores propagation after each exit.

Was this helpful? React 👍 or 👎

_{Open Bits AI session}

_{🤖 Datadog Autotest · Commit 9c27dfe · What is Autotest? · @DataDog review to ask questions · Any feedback? Reach out in #autotest}

[datadog-prod-us1-6]

🎯 Code Coverage (details)
• Patch Coverage: 100.00%
• Overall Coverage: 69.74% (+10.60%)

_{This comment will be updated automatically if new data arrives.
🔗 Commit SHA: 9c27dfe | 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	14.00 s	14.00 s	[-0.9%; +0.9%] (no difference)
startup:insecure-bank:tracing:Agent	12.90 s	12.99 s	[-1.4%; +0.1%] (no difference)
startup:petclinic:appsec:Agent	16.93 s	16.27 s	[-0.3%; +8.4%] (no difference)
startup:petclinic:iast:Agent	16.88 s	16.91 s	[-1.0%; +0.6%] (no difference)
startup:petclinic:profiling:Agent	16.67 s	16.87 s	[-2.5%; +0.1%] (no difference)
startup:petclinic:sca:Agent	16.88 s	16.71 s	[+0.0%; +2.0%] (maybe worse)
startup:petclinic:tracing:Agent	15.97 s	15.96 s	[-0.9%; +1.1%] (no difference)

Commit: 9c27dfed · 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.