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From: vlsi (@vlsi) <[email protected]>
To: pgjdbc/pgjdbc <[email protected]>
Subject: [pgjdbc/pgjdbc] PR #3886: fix: avoid memory leaks in Java <= 21 caused by Thread.inheritedAccessControlContext
Date: Wed, 03 Dec 2025 08:14:22 +0000
Message-ID: <[email protected]> (raw)

`Thread.inheritedAccessControlContext` inherits the caller `ProtectionDomain`, thus it effectively holds its classloader.
There's no way to "unset `inheritedAccessControlContext`".

We workaround that by going for ForkJoinPool + ManagedBlocker so it is JDK that creates a thread, thus it should have no `inheritedAccessControlContext`.

The logic is as follows:
1) ForkJoinPool task runs on CPU and it processes the queue
2) If the queue is empty, the blocking call delegates to ManagedBlocker

It fits nice with FJP: CPU tasks do not create extra threads, and blocking queue operations do not starve FJP CPU threads.

See https://stackoverflow.com/questions/78163385/does-postgres-jdbc-lazycleaner-cause-a-classloader-memo...

---

An alternative option could be going for native `java.lang.ref.Cleaner` when running with Java 9+, however, it would still be nice to have a solution for Java 8.


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