binhuiliu commented on issue #12246:
URL: https://github.com/apache/gravitino/issues/12246#issuecomment-5164279367
I completed an accelerated local reproduction against a clean Apache
Gravitino v1.3.0 checkout using the embedded Hive Metastore.
- Created, used, and closed 5 independent `HiveClientFactory` instances.
- After repeated GC and allocation pressure, all 5 corresponding
`HiveClientClassLoader` instances remained alive.
- `Log4jLoggerFactory.registry` contained multiple classloader-specific
`LoggerContext` entries.
- As a diagnostic control only, removing the registry references and
repeating the same GC procedure reduced the surviving classloaders from 5/5 to
0/5.
This confirms that, in this reproducer, the Log4j SLF4J adapter registry is
sufficient to retain the closed classloaders. No thread interruption or
ThreadLocal cleanup was required for the classloaders to become collectible
after those registry references were removed.
I also tested targeted cleanup through the public Log4j lifecycle API:
```java
@Override
public void close() throws IOException {
try {
LogManager.shutdown(LogManager.getContext(this, false));
} finally {
super.close();
}
}
```
Placing this in `HiveClientClassLoader.close()` covers both normal factory
shutdown and temporary classloaders closed during Hive-version detection or
fallback.
The Log4j `AbstractLoggerAdapter` is registered as a `LoggerContext`
shutdown listener. Shutting down the specific context therefore removes only
that context from `Log4jLoggerFactory.registry`; it does not clear the JVM-wide
logging state.
A two-factory isolation test also passed:
- Closing factory A removed the logger context for A and allowed its
classloader to be collected.
- The context for factory B remained registered.
- Factory B continued querying the Hive Metastore successfully.
The focused diagnostic test, `TestCachedClientPool`, `TestHiveClientPool`,
compilation, and Spotless checks passed.
This candidate requires `compileOnly(libs.log4j.api)` in
`hive-metastore-common`. Docker-based Hive 2/Hive 3, repeated-close,
concurrency, and Kerberos/impersonation validation have not yet been run.
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