Hi guys. We keep getting this in our Tomcat catalina.out log file:
6283020 [Timer-135] DEBUG com.mchange.v2.resourcepool.BasicResourcePool - Checking for expired resources - Mon Oct 29 12:56:52 GMT 2007 [com.mchange.v2.resourcepool.BasicResourcePool@16f3619]
6283020 [Timer-135] DEBUG com.mchange.v2.resourcepool.BasicResourcePool - BEGIN check for expired resources. [com.mchange.v2.resourcepool.BasicResourcePool@16f3619]
6283020 [Timer-135] DEBUG com.mchange.v2.resourcepool.BasicResourcePool - FINISHED check for expired resources. [com.mchange.v2.resourcepool.BasicResourcePool@16f3619]
I believe this is from JForum, as the rest of our applications don't use log4j as far as I'm aware. We are using SSO and a session timeout of 30 min. What does this log entry mean? Thanks a lot for any help! [originally posted on jforum.net by akindo]
A quick guess would be that this is the code that handle DB connection pooling doing some housekeeping. With DB connection pooling, there is a "pool manager" that keeps a set of open connections to the DB and hand them out to applications as needed.
This helps performance because it eliminates the high overhead of establishing a connection to the database server for each request. This can be 30-50% of the time/CPU cycles on a non-pooled connection.
One issue that a pool manager needs to deal with is "stale" connections. E.g., connections that might have timed out (expired) due to inactivity. That is what these messages seem to be indicating.
FWIW, they are DEBUG messages. If you want to cut back on info logged, you can change your logging setting to INFO or higher. (Or get fancy and set levels based on package names, e.g. com.mchange.v2 to info). [originally posted on jforum.net by monroe]
You are probably right, seems logical about checking for DB connections. We did enable connection pooling for this JForum webapp. Once we get one of these entries, they seem to continue (I can see this in my Eclipse Console window, get a new entry every second or so). I see we are also getting: