[JCR-2768] Finalize method on SessionImpl

• Type: Improvement
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 2.1
• Component/s: jackrabbit-core
• Assignee: Unassigned
• Reporter: Douglas Britsch
• Created: 05/Oct/10 22:57
• Updated: 06/Dec/16 17:02

Description

Doing some profiling on our application which uses Jackrabbit-2.1.0 I noticed that there were an awful lot of java.lang.ref.Finalizer objects hanging around. Digging around I found the culprit was a finalize method on SessionImpl. While I can see what it is trying to do (close the session if you have not called logout) , I have found in the past that on application servers, finalize should be avoided for objects that are created and deleted frequently, as the GC behavior and object allocation is severely impacted, and because of the number of references held by the session this seems like it could keep a lot more in memory than needed a lot longer. (for more info see http://www.fasterj.com/articles/finalizer1.shtml ).

Per Jukka's suggestion on the mailing list "
The automatic closing of a discarded session and related the warning
message are pretty useful in practice, as there are quite a few
session leaks in many client applications. So I'd rather keep that
functionality.

If the finalizer causes problems, we could investigate using weak (or
perhaps phantom) references and a reference queue for this purpose.
The RepositoryImpl class already keeps weak references to all sessions
in the activeSessions map, so this shouldn't even be too difficult to
implement."

Issue Links

• is related to: SLING-3285 ResourceResolver.isResourceType() creates admin session for every call with super type, slowing down processing
• is related to: SLING-4372 The use of finalize in ResourceResolver leads to performance issues
• relates to: OAK-1349 No warning on unclosed sessions in Oak