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From Michael Thomson <>
Subject Re: [POOL] Problem when blocking waiting to borrow from pool
Date Wed, 18 Oct 2006 19:24:46 GMT

I think you have spotted the "obvious" bug..... thank you.  I am an 
idiot :-).  There is method level syncronization which is causing my 
problem, I'm sure.  I will check and confirm to the list.

I am using pool 1.3 implementation.

Thank you all for your input.


Sandy McArthur wrote:
> Michael,
> What you are describing, if true, is a serious bug. My gut is that the
> bug isn't with the GenericObjectPool code because I expect it would
> have been reported by now.
> Without code that demonstrates the bug (aka:unit test) it's hard to
> know anything for sure but the first thing that comes to mind is:
> GenericObjectPool is supposed to be thread-safe out of the box, if you
> are adding any synchronization, such as calling pool.borrowObject from
> with in your own synchronized block, then you could get the behavior
> you describe. When a thread acquires a couple of locks by passing into
> a synchronized block, calling Object.wait() only releases that one
> lock and not all that have been acquired.  GenericObjectPool only
> knows about it's internal locks and cannot release any of your code's
> locks while it waits. This could create the inactivity you describe.
> Also, make sure you are using the latest Pool release (1.3) and if you
> can generate a javacore (`kill -3 javapid` or ctrl+\ on unix, or
> ctrl+break on windows) you should be able to see where the Threads are
> waiting to acquire locks.
> Hope that helps some.
> On 10/18/06, Michael Thomson <> wrote:
>> Hi,
>> I have an app running in JBOSS
>> I am trying to use the GenericObjectPool.
>> I have two "user" objects and one "pool" object
>> MaxActive =1
>> pool.setWhenExhaustedAction(pool.WHEN_EXHAUSTED_BLOCK)
>> It appears that when one "user" object is blocked waiting on a
>> borrowObject() when the other "user" object attempts to returnObject(),
>> both "user" objects "hang" until the maxWait time is reached?
>> I can go into more detail if anyone thinks it will help.
>> Anyone seen this problem, or have any suspicions, is JBoss likely to be
>> interfering with anything here, anyone doing anything similar, it seems
>> like a very basic use case?
>> Thanks in Advance,
>> Michael
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