KTOR-9290 Jetty Jakarta idleTimeout does not cancel the request's job

[amccague]

Subsystem
Jetty Jakarta Ktor Server

Motivation
https://youtrack.jetbrains.com/issue/KTOR-9290/Jetty-Jakarta-idleTimeout-does-not-cancel-the-requests-job

When Jetty's idle timeout expires during request processing, the timeout is effectively ignored if the server-side coroutine is performing slow work. Clients would still receive the intended status code beyond the idle timeout time.

The current tests are focussed on clients being slow to read and write.

The fix adds an idle timeout listener to the Jetty request that cancels the handler's coroutine job when the timeout fires therefore making it effective on server resources.

[coderabbitai]

Walkthrough

Adds idle-timeout-driven cancellation of the coroutine launched for request handling in the Jetty Jakarta handler and centralizes guarded error-write logic; adds a test that verifies idle timeout cancels the coroutine and unwraps the resulting CancellationException root cause.

Changes

Cohort / File(s)	Summary
Handler Implementation ktor-server/ktor-server-jetty-jakarta/jvm/src/io/ktor/server/jetty/jakarta/JettyKtorHandler.kt	Capture the coroutine job returned from application.launch; add an idle-timeout listener that cancels that job and triggers guarded error writing; refactor cancellation and general error paths to use a new private helper tryWriteError which guards response.isCommitted and uses runCatching.
Test Coverage ktor-server/ktor-server-jetty-jakarta/jvm/test/io/ktor/tests/server/jetty/jakarta/JettyIdleTimeoutTest.kt	Enable SSL-disabled test setup; add idleTimeoutCancelsCoroutineContext() test asserting idle timeout cancels the server coroutine and that the caught CancellationException unwraps to a TimeoutException; convert mutable writeError to val; add afterTest handling to swallow expected CancellationException for that test; add CancellationException.unwrapRootCause() helper.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Suggested reviewers

• bjhham
• marychatte

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 25.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and specifically describes the main change: adding idle timeout cancellation for Jetty Jakarta requests, directly referencing the issue KTOR-9290.
Description check	✅ Passed	The description includes all required template sections with substantive content: Subsystem, Motivation (with issue link and problem description), and Solution (explaining the timeout listener fix).

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✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment

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[amccague]

I should say I'm not a fan of this 410 Gone here - I can't see how a cancellation exception should imply

the target resource is no longer available at the origin server and that this condition is likely to be permanent

https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status/410

408 probably fits better.. but in this context we can't be sure how this bubbled up so it could be a 500 like the others.

[coderabbitai]

Actionable comments posted: 1

🤖 Fix all issues with AI agents

In
`@ktor-server/ktor-server-jetty-jakarta/jvm/test/io/ktor/tests/server/jetty/jakarta/JettyIdleTimeoutTest.kt`:
- Around line 39-41: The comment in JettyIdleTimeoutTest.kt contains a typo:
change "unhanded" to "unhandled" in the KDoc above the test (the block
mentioning afterTest override); locate the comment near the class/test that
overrides afterTest and correct the word to "unhandled" so the sentence reads
"how an unhandled CancellationException is handled" to fix the typo.

🧹 Nitpick comments (1)

ktor-server/ktor-server-jetty-jakarta/jvm/test/io/ktor/tests/server/jetty/jakarta/JettyIdleTimeoutTest.kt (1)

17-18: Redundant import: CancellationException is already covered by the star import.

Line 18 explicitly imports kotlinx.coroutines.CancellationException, but Line 17's star import kotlinx.coroutines.* already includes it.

🧹 Suggested fix

 import kotlinx.coroutines.*
-import kotlinx.coroutines.CancellationException