RE: Tomcat threads - waiting on monitor entry

[Pugalia, Jai P \(JP\)]

Hi,

After further investigation, I have realized that all the threads are
blocked due to one thread which has the following stack trace:

"http-8443-Processor19" daemon prio=1 tid=0xa948b688 nid=0x884 in
Object.wait() [a71d4000..a71d5878]
        at java.lang.Object.wait(Native Method)
        - waiting on <0xab5d4c80> (a
org.apache.commons.pool.impl.GenericObjectPool)
        at java.lang.Object.wait(Object.java:429)
        at
org.apache.commons.pool.impl.GenericObjectPool.borrowObject(GenericObjec
tPool.java:748)
        - locked <0xab5d4c80> (a
org.apache.commons.pool.impl.GenericObjectPool)
        at
org.apache.commons.dbcp.PoolingDriver.connect(PoolingDriver.java:175)
        at java.sql.DriverManager.getConnection(DriverManager.java:512)
        - locked <0xaf5bcf10> (a java.lang.Class)
        at java.sql.DriverManager.getConnection(DriverManager.java:193)
        - locked <0xaf5bcf10> (a java.lang.Class)
        at
com..coreservice.db.PooledDBConnection.getConnection(PooledDBConnection.
java:159) 
      ....

This particular thread appears to be waiting in the GenericObjectPool
(commons-pool class).

Any suggestions on what could be the problem? 

Thanks a lot,
JP

-----Original Message-----
From: Pugalia, Jai P (JP) 
Sent: Wednesday, July 27, 2005 6:48 PM
To: Tomcat Users List
Subject: Tomcat threads - waiting on monitor entry 

Hi,

We have an web application running under Tomcat (5.0.28) on Red Hat
Linux and uses Postgres database (8.0).
For database connection pooling we use commons-dbcp (1.2.1) and
commons-pool(1.2.1)

After some time of high-usage, the web application stops responding. 

Dumping of the thread stack traces shows several http threads locked in
a particular DBCP call:

"http-8443-Processor10" daemon prio=1 tid=0xa949bb60 nid=0x884 waiting
for monitor entry [a765c000..a765e878]
        at java.sql.DriverManager.getConnection(DriverManager.java:187)
        - waiting to lock <0xaf5bcf10> (a java.lang.Class)
        at
com.coreservice.db.PooledDBConnection.getConnection(PooledDBConnection.j
ava:159)

Has anyone else seen these locks? Are we missing something about
DBCP/pool configuration and usage under Tomcat?

Any suggestions?
JP

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