[POOL-327] GKOP: returnObject does not unblock threads waiting in borrowObject if maxIdle=0

• Type: Bug
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 2.4.2
• Fix Version/s: 2.6.1
• Assignee: Mark Struberg
• Reporter: Paul Pazderski
• Created: 19/Jun/17 11:47
• Updated: 29/Oct/18 19:14
• Resolved: 28/Oct/18 11:54

Description

If idle objects are disabled by maxIdle=0 a thread blocked in borrowObject is not notified if another thread returns an object.

Attached is a unit test (327-maxIdle0-test.patch) that demonstrates the issue. I tried a similar test on GenericKeyedObjectPool as well which not seems to be affected by this issue.

I also attached two possible solutions for this issue.
The first (327-maxIdle0.patch) just notifies a potentially waiting thread in the affected returnObject code branch. (similar to POOL-240)

The second (327-maxIdle0-alternativ.patch) checks for waiting threads every time an object get destroyed. But this may introduce undesired behavior in other functions. (like clear or evict)

Issue Links

• is superceded by: POOL-356 deadlock if borrowObject gets called to fast and maxIdle is 0