Paul King created GROOVY-12280:
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Summary: AwaitableAdapterRegistry.awaitableCache pins the Groovy
class loader via ClassValue associations on platform-class keys
Key: GROOVY-12280
URL: https://issues.apache.org/jira/browse/GROOVY-12280
Project: Groovy
Issue Type: Bug
Reporter: Paul King
{{AwaitableAdapterRegistry}} caches adapter lookups in a raw
{{java.lang.ClassValue}} keyed by the awaited object's class. The common keys
are platform classes — {{CompletableFuture}}, {{CompletionStage}},
{{Flow.Publisher}} implementations — while the cached value (the adapter
instance) is loaded by Groovy's class loader. A {{ClassValue}} association
lives as long as its key class
([JDK-8136353|https://bugs.openjdk.org/browse/JDK-8136353], working as
intended), so an association on an effectively immortal platform class holds
the adapter, and through it the entire Groovy class loader, for the lifetime of
the JVM. In the per-webapp deployment topology this re-creates exactly the
pinning GROOVY-12142 removed elsewhere: metaspace growth on every redeployment
once any {{await}} has executed.
Note this site is not covered by the {{groovy.use.classvalue=false}} escape
hatch restored in GROOVY-12142 — it does not go through
{{GroovyClassValueFactory}} (which is package-private in
{{org.codehaus.groovy.reflection}} and not reachable from
{{groovy.concurrent}}).
Unlike the general {{ClassInfo}} problem (see the companion investigation
ticket), the preconditions for the {{SoftReference}} strategy are already
satisfied here by construction: recomputation is a cheap, pure scan over the
adapter list, and the registry already rebuilds the cache on mutation. Proposed
fix: wrap values in {{SoftReference}} with the check-remove-recompute
discipline (on a cleared reference, {{remove(...)}} the association and
recompute), optionally also widening {{GroovyClassValueFactory}} so this site
honors the escape hatch for consistency.
Follow-up from review discussion on [PR
#2798|https://github.com/apache/groovy/pull/2798] (GROOVY-12142).
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