[POOL-38] Deadlock

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Invalid

Environment

10 Threads, Default Configuration

• Assignee: Sandy McArthur Jr
• Reporter: Fuad Efendi
• Created: 16/May/06 10:20
• Updated: 03/Feb/08 16:44
• Resolved: 20/May/06 22:55

Description

Here is the use case:

• 8 Threads
• Each Thread needs 2 objects from a pool
• Pool has limit: 8 objects (default for DBCP)
• After receiving first object from a pool, Thread calls wait() method on GenericObjectPool, to get access to released object
• All Threads are waiting... (deadlock)

I found it by running simple test with Hibernate & Spring, Hibernate needs second Connection to retrieve primary key from a database in a separate context. Anyway, synchronize/wait/notify IS NOT a best practice (2006, May).

org.apache.commons.pool.impl.GenericObjectPool.borrowObject() - line 810

MISTAKE at http://jakarta.apache.org/commons/dbcp/configuration.html:
maxActive = "The maximum number of active connections that can be allocated from this pool at the same time, or zero for no limit. "

• should be -1 instead of 'zero for no limit'. However, it does not help if I need to limit number of objects in a pool...

Weak docs are a bug also... please note time spending for troubleshooting such tricky deadlocks...

Cheers,
Fuad Efendi

Issue Links

• duplicates: POOL-1 Deadlock