Improve `Queue.maintain` performance by introducing cache for `Util.isOverridden` by sghill · Pull Request #26797 · jenkinsci/jenkins

sghill · 2026-05-16T22:22:44Z

Adds a method to check the size so cache monitoring can be easily wired into observability tools. Also adds a method to clear cache so it could be called from Jenkins script console if necessary. Happy to add a feature flag or make other changes if desired.

Testing done

Automated tests added and mvn verify passed.

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After

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Proposed changelog entries

Cache calls to Util.is Overridden to improve Queue.maintain performance.

Proposed changelog category

/label internal

Proposed upgrade guidelines

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The issue, if it exists, is well-described.
The changelog entries and upgrade guidelines are appropriate for the audience affected by the change (users or developers, depending on the change) and are in the imperative mood (see examples). Fill in the Proposed upgrade guidelines section only if there are breaking changes or changes that may require extra steps from users during upgrade.
There is automated testing or an explanation as to why this change has no tests.
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For dependency updates, there are links to external changelogs and, if possible, full differentials.
For new APIs and extension points, there is a link to at least one consumer.

Desired reviewers

@timja for being the initial reviewer on a similar change for this setup in #11032

Before the changes are marked as ready-for-merge:

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If it would make sense to backport the change to LTS, be a Bug or Improvement, and either the issue or pull request must be labeled as lts-candidate to be considered.

Copilot

Pull request overview

This pull request aims to reduce Queue.maintain contention by caching Util.isOverridden results (avoiding repeated reflective lookups), and adds small APIs to observe and clear that cache.

Changes:

Add an isOverridden result cache in hudson.Util and route isOverridden through it.
Add cache observability/maintenance methods (isOverriddenCacheSize, clearIsOverriddenCache).
Add JUnit tests covering cache hit/miss behavior and cache keying.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
core/src/main/java/hudson/Util.java	Introduces the `isOverridden` cache plus cache size/clear methods.
core/src/test/java/hudson/util/IsOverriddenTest.java	Adds unit tests validating caching behavior and cache key composition.

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timja · 2026-05-17T07:16:49Z

+    // Keyed by (base, derived, methodName, paramTypes). Derived is held weakly so that plugin
+    // classloaders remain GC-eligible after unload. Results are stable for the lifetime of a
+    // classloader, so no invalidation is needed.
+    private static final ConcurrentHashMap<IsOverriddenCacheKey, Boolean> IS_OVERRIDDEN_CACHE =
+            new ConcurrentHashMap<>();
+
+    private record IsOverriddenCacheKey(
+            Class<?> base,
+            WeakReference<Class<?>> derivedRef,
+            String methodName,
+            List<Class<?>> types) {
+
+        @Override
+        public boolean equals(Object o) {
+            if (!(o instanceof IsOverriddenCacheKey other)) return false;
+            return base == other.base
+                    && derivedRef.get() == other.derivedRef.get()
+                    && methodName.equals(other.methodName)
+                    && types.equals(other.types);
+        }
+
+        @Override
+        public int hashCode() {
+            // Identity hash matches the identity comparison in equals.
+            return Objects.hash(base, System.identityHashCode(derivedRef.get()), methodName, types);
+        }


if/ once this is merged it should be possible to use caffeine if that is helpful: #26600

Thanks for the review!

I can make that change, or a periodic task (hourly?) to call clear on the cache. Let me know if either are desired.

I wasn't too concerned without having expiry because it's very rare for me to unload a plugin without restarting Jenkins. I'm sure you'll have a better idea of how common this is across users of Jenkins, so happy to defer to you.

tbh I don't think you can unload a plugin. May not be necessary

timja

Seems fine.

Did you notice any improvement in testing?

sghill · 2026-05-19T06:41:32Z

@timja I'm seeing a 96% reduction with the cache in a JMH Benchmark I ran on my laptop (3 forks, 5 warmup iterations, 10 measured iterations). I tried to create the conditions I saw issues with on the controller - about 1000 builds in the queue for FreeStyleProjects.

Java 21.0.11-temurin
OS: Fedora 43
CPU: i7-10710U @ 1.10 GHz w/ 6 cores
Arch: x86_64
Built with: mvn -pl war install -DskipTests -Dcheckstyle.skip -am
Tested with: mvn -pl test test -Dtest=IsOverriddenBenchmarkTest -DfailIfNoTests=false -Dcheckstyle.skip -am

sghill · 2026-05-20T19:24:36Z

Is this the sort of change we might consider for a LTS backport?

timja · 2026-05-20T19:38:30Z

possibly but its not likely to make the next LTS patch version and as long as its in soon-ish it'll be in the next LTS baseline

MarkEWaite

This PR is now ready for merge. We will merge it after approximately 24 hours if there is no negative feedback. Please see the merge process documentation for more information about the merge process.

/label ready-for-merge

Introduce cache for Util.isOverridden

ed0445c

comment-ops-bot Bot added the internal label May 16, 2026

timja requested a review from Copilot May 17, 2026 06:57

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timja requested a review from a team May 18, 2026 09:29

MarkEWaite approved these changes May 24, 2026

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comment-ops-bot Bot added the ready-for-merge The PR is ready to go, and it will be merged soon if there is no negative feedback label May 24, 2026

This was referenced May 24, 2026

BOM and ATH test several pull requests #26831

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Test several core pull requests jenkinsci/acceptance-test-harness#2725

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MarkEWaite added the ath-successful This PR has successfully passed the full acceptance-test-harness suite label May 24, 2026

MarkEWaite mentioned this pull request May 25, 2026

Test several pull requests to Jenkins core jenkinsci/bom#6852

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MarkEWaite added the pct-successful This PR has successfully passed the full plugin-compatibility-test suite label May 25, 2026

MarkEWaite merged commit cc0aad6 into jenkinsci:master May 25, 2026
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This was referenced Jun 2, 2026

Test Jenkins core with Winstone and Jetty 12.1.10 jenkinsci/acceptance-test-harness#2737

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Test Jenkins core with Winstone and Jetty 12.1.10 jenkinsci/bom#6894

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Improve `Queue.maintain` performance by introducing cache for `Util.isOverridden`#26797

Improve `Queue.maintain` performance by introducing cache for `Util.isOverridden`#26797
MarkEWaite merged 1 commit into
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sghill:perf/cache-is-overridden

sghill commented May 16, 2026 •

edited by krisstern

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sghill commented May 16, 2026 •

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