QiuYucheng2003 opened a new issue, #15031:
URL: https://github.com/apache/iceberg/issues/15031
### Apache Iceberg version
main (development)
### Query engine
None
### Please describe the bug 🐞
### Context
The `org.apache.iceberg.util.ThreadPools` class maintains static
`ExecutorService` instances (`WORKER_POOL` and `DELETE_WORKER_POOL`) that are
initialized statically and persist for the lifetime of the JVM.
### Problem
These thread pools are created using
`MoreExecutors.getExitingExecutorService`, which registers a **JVM shutdown
hook** to terminate the threads. However, there is no public API to explicitly
shut down these pools when the Iceberg library is unloaded or when the
application using Iceberg is stopped (without killing the JVM).
### Impact
In environments that support hot-reloading or dynamic lifecycles (e.g.,
Tomcat Web Containers, Flink clusters, OSGi), the JVM does not exit when an
application is undeployed.
1. The static thread pools remain active.
2. The threads inside these pools retain references to their
`inheritedAccessControlContext` or `contextClassLoader`.
3. This prevents the application's `ClassLoader` from being garbage
collected.
4. Repeated redeployments lead to a **ClassLoader Leak** and eventually
`java.lang.OutOfMemoryError: Metaspace`.
### Analysis from Source Code
In `ThreadPools.java`:
```java
private static final ExecutorService WORKER_POOL =
newExitingWorkerPool("iceberg-worker-pool", WORKER_THREAD_POOL_SIZE);
The WORKER_POOL is private static final and depends solely on SystemConfigs.
There is no mechanism to release these resources programmatically.
### Willingness to contribute
- [x] I can contribute a fix for this bug independently
- [ ] I would be willing to contribute a fix for this bug with guidance from
the Iceberg community
- [ ] I cannot contribute a fix for this bug at this time
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