Kezhu Wang created FLINK-20614:
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Summary: Registered sql drivers not deregistered after task
finished in session cluster
Key: FLINK-20614
URL: https://issues.apache.org/jira/browse/FLINK-20614
Project: Flink
Issue Type: Bug
Components: Connectors / JDBC, Runtime / Task
Affects Versions: 1.12.0, 1.13.0
Reporter: Kezhu Wang
{{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|https://ci.apache.org/projects/tomcat/tomcat85/docs/jndi-datasource-examples-howto.html#DriverManager,_the_service_provider_mechanism_and_memory_leaks]
and fixes/circumvents this with
[JdbcLeakPrevention|https://github.com/apache/tomcat/blob/master/java/org/apache/catalina/loader/JdbcLeakPrevention.java#L30].
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.
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