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From Niall Gallagher <>
Subject Re: DBCP connection pool problem
Date Tue, 29 May 2007 16:58:05 GMT

Yep, the issue we were seeing was caused when the eviction time was too 
low, this needs to be kept higher than a couple of seconds (I would 
recomend 30). This causes problems in two scenarios:

1) When starting up the min idle was created twice
2) When eviction took place the evictor evicted idle connections then 
forced the pool back up to min idle which caused a cycle of connections 
to be created

Also, we noticed a slight bug in our code which made the problem worse. 
We created too many DataSource objects due to a slight synchronization 
bug. This caused us to create several data sources, all of which had a 
configured eviction time of about 500 ms, this caused many 
evictions/creations every second and thats what caused our problem


Ravi116 wrote:
> Niall,
> I am encountering a similar issue with DB2. Running our appln inside of
> Tomcat/Spring JDBC. Niall - Did u resolve/find out more abt the issue ? Any
> help is appreciated.
> Ravi
> Niall Gallagher-3 wrote:
>> Hi All,
>> I am using the latest commons DBCP library (1.2.1) as our connection 
>> pooling solution for an Oracle DB. However I am encountering a strange 
>> issue where under certain conditions DBCP seems to open an excessive 
>> amount of connections to the DB. We are not sure exactly what is causing 
>> the problem but we suspect that it is the Evictor task within the 
>> commons-pool library.
>> When the issue occurs the TNS listener logs for Oracle show an massive 
>> growth in the number of connections being attempted. For instance here 
>> is the activity over a couple of minutes.
>> 03-JAN-2007, 16:48, db1,, 52858
>> 03-JAN-2007, 16:49, db1,, 61696
>> 03-JAN-2007, 16:50, db1,, 61107
>> 03-JAN-2007, 16:51, db1,, 61475
>> 03-JAN-2007, 16:52, db1,, 61446
>> On average about 60,000 connections a minute. We are quite certain this 
>> is caused by DBCP as this is the only means of accessing DB connections 
>> within our applications and we log before and after the 
>> DataSource.getConnection method (our logs show no repetitive log 
>> statements).  Has anyone seen such an issue before? Any help on this 
>> would be greatly appreciated.
>> Thanks,
>> Niall
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