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https://issues.apache.org/jira/browse/GROOVY-12142?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18105189#comment-18105189
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ASF GitHub Bot commented on GROOVY-12142:
-----------------------------------------
paulk-asert opened a new pull request, #2798:
URL: https://github.com/apache/groovy/pull/2798
âŚr and DFA-cache-cleaner threads, restore the ClassValue escape hatch
A Groovy copy deployed per webapp (the common Tomcat/WEB-INF/lib topology)
permanently pinned its class loader, growing metaspace on every parallel
(re)deployment. Three independent pins:
1. PIC-Cleaner: linking any indy call site started a never-terminating
daemon thread from CacheableCallSite's static initializer, pinning the defining
loader and capturing the creating context's protection domains. Stale PIC
entries are now swept inline â both callers already hold the lruCache monitor
and the cache is bounded (8), so the sweep is trivial; the
groovy.indy.callsite.cleaner.inline flag (GROOVY-12092) is gone along with the
thread it toggled, which also removes the parked-thread false positive it
existed to avoid.
2. DFA-cache-cleaner: each AtnManager started a never-terminating
reference-queue thread whose catch-all swallowed even interrupts. The softly
referenced AtnWrapper is a GC canary; its collection is now detected on the
parse path when the soft reference reads null, clearing the shared DFA cache at
the next parse instead of at GC time â no queue, no thread.
3. java.lang.ClassValue associations on immortal (bootstrap) classes never
release their value's class loader (JDK-8136353), so one dynamic dispatch on
e.g. String pinned the loader. The groovy.use.classvalue=false escape hatch
(present through 4.x, lost in the GROOVY-11520 collections cleanup) is
restored, with the fallback rebuilt on ManagedIdentityConcurrentMap (~40 lines)
rather than the removed deprecated collections. Default stays ClassValue.
With 1+2 fixed, a dropped loader is collectable either with the flag or with
a shutdown sweep over ClassInfo.getAllClassInfo() calling ClassInfo.remove â
both verified by classloader-churn harness against the rebuilt jar;
out-of-the-box default config still requires one of the two (the JVM bug is not
ours to fix).
> Metaspace memory leak with parallel deployments on Tomcat
> ---------------------------------------------------------
>
> Key: GROOVY-12142
> URL: https://issues.apache.org/jira/browse/GROOVY-12142
> Project: Groovy
> Issue Type: Bug
> Affects Versions: 4.0.24, 4.0.29
> Environment: Tomcat: 10.1.55
> openjdk version "17.0.19" 2026-04-21 LTS
> OpenJDK Runtime Environment (Red_Hat-17.0.19.0.10-1) (build 17.0.19+10-LTS)
> OpenJDK 64-Bit Server VM (Red_Hat-17.0.19.0.10-1) (build 17.0.19+10-LTS,
> mixed mode, sharing)
> Reporter: Jan Gosmann
> Priority: Major
> Attachments: Screenshot 2026-07-09 at 09.46.46.png, spring-test.tar.gz
>
>
> We are using [Tomcat parallel
> deployments|https://tomcat.apache.org/tomcat-10.0-doc/config/context.html#Parallel_deployment]
> to achieve downtimeless deployments. However, we with each new deployment
> the metaspace grows (see attached image). Even after undeploying the old
> version it does not shrink. If we configure a maximum metaspace size, new
> parallel deployments fail with an out-of-memory error.
> I was able to reproduce this with a very simple Spring Boot application
> (attached). As long as I had no Groovy in there, metaspace was reclaimed
> before hitting the maximum on new deploys. After introducing Groovy,
> metaspace is no longer reclaimed.
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