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From Kaleb Pederson <>
Subject Tomcat becoming almost completely non-responsive
Date Fri, 01 Oct 2004 22:07:50 GMT

I have an interesting problem.  After a while, tomcat (5.0.27) becomes almost 
completely non-responsive.  If I telnet in to port 8009  (I'm using apache 
and mod_jk2), I get no response, at least not within the default timeout.  If 
a browse to a page, I will generally, after about 4-5 minutes, see a page 

To narrow down the slowness, I generated a full thread dump, and found the 
following information:

[ see attachment for more info]
Total threads: 180
executeQuery: 2 //  executing a db query
validateConnection: 0 // trying to validate their connection
validateObect: 48 // in commons.dbcp.PoolableConnectionFactory.validateObject
socketAccept: 3 // accepting a socket
socketRead0: 10 // reading a socket
ReferenceQueue: 1
ThreadPool$MonitorRunnable: 2
borrowObject and Object.wait: 85 // trying to get an object from the pool
Object.wait: 20 // threads just waiting around
Remaining:  9 // misc. threads

My database connection is setup so that I have 50 allowed connections, which 
matches my 48 in validateObject and 2 executing queries.  However, when I 
query the database status, I see 2 active threads and the rest are 
'sleeping', just waiting around, as they would be if the connection pool 
hadn't released them yet.

So, why would there be 48 connections that seemed locked and weren't querying 
the DB?  And then the other 85 that were seemingly waiting on the 45?  Any 
ideas what might be going on?  The DB is ready?  I have log abandoned turned 
and an haven't seen a problem yet.  If the load drops sufficiently on the 
server, everything eventually returns back to normal, otherwise it takes 5-10 
minutes to get a response from the server.

I have attached an abbreviated form of the thread dump which should provide 
all the critical information and can provide as much other information as is 

Thanks for the help.  *All* suggestions welcome ;)


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