[FLINK-20614] Registered sql drivers not deregistered after task finished in session cluster

• Type: Bug
• Status: Open
• Priority: Not a Priority
• Resolution: Unresolved
• Affects Version/s: 1.12.0, 1.13.0
• Component/s: Connectors / JDBC, Runtime / Task
• Labels: auto-deprioritized-critical auto-deprioritized-major auto-deprioritized-minor
• Assignee: Unassigned
• Reporter: Kezhu Wang
• Created: 16/Dec/20 00:27
• Updated: 04/Feb/22 22:36

Description

DriverManager keeps registered drivers in its internal data structures which prevents they from gc after task finished. I confirm it in standalone session cluster by observing that ChildFirstClassLoader could not be reclaimed after several GC.run, it should exist in all session clusters.

Tomcat documents this and fixes/circumvents this with JdbcLeakPrevention.

Should we solve this in runtime ? Or treat it as connector and clients' responsibility to solve it using RuntimeContext.registerUserCodeClassLoaderReleaseHookIfAbsent or similar ?

Personally, it would be nice to solve in runtime as a catch-all to avoid memory-leaking and provide consistent behavior to clients cross per-job and session mode.