[POOL-108] GenericObjectPool does per-resource work (e.g. validate) in a synchronized context

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 1.3
• Fix Version/s: 1.4
• Assignee: Unassigned
• Reporter: Matthew Moore
• Created: 12/Nov/07 18:03
• Updated: 12/Sep/10 17:43
• Resolved: 10/Dec/07 02:59

Description

While using the pool library with DBCP, and load testing with simulated failures, we noticed that a single bad connection can cause multiple threads to block when the test on borrow flag is true. (Using "select 1" as a test query.)

Looking at the code, GenericObjectPool performs activation, passivation, and validate on both borrow and return, inside of synchronized methods. This can be a real problem, since any of these operations could conceivably block, in which case all threads trying to obtain or release a resource will also block for the duration. Some of these concerns are indirectly covered by POOL-93 in 2.0. Looking at revision 594226 I can see this has not yet been addressed.

Narrowing the synchronization scope via synchronized blocks, rather than synchronizing the entire method, would deal with this easily enough. If I get the time I'll work up a patch. This should be addressed - in the context of DBCP it turns test on return / borrow into counter-intuitively dangerous options.

Issue Links

• blocks: DBCP-206 DBCP high performance contention point