CODEWITHSUNDEEP
javamysqltomcatjdbcmemory-leaks
kvgeorge1
kvgeorge1

Reputation: 33

Tomcat jdbc connection pool - Pool-Cleaner Memory Leak

I have scoured the internet for over a day and still cannot seem to find a working solution. I am using MySQL Connector/J 5.1.35 and Tomcat JDBC Connection Pool with Tomcat 6.0.32 and I am not able to start/stop/reload an existing Web Application without the tomcat jdbc cleaner pool thread not being able to be stopped and causing memory leaks. I have tried everything that I could find on the net about it and I still have the same issues. If I stop the container, it wouldn't matter since once the container stops, the threads are dead. BUT, since I am not stopping the container, just merely stopping the application, BAM! - Memory Leak.

This is beyond frustrating and you would think that Apache would have a detailed solution for this, but they don't.

Anyone know how to resolve this once and for all?

Oh, and yes - I de-register the drivers and run AbandonedConnectionCleanupThread.shutdown() in a ServletContextListener and have tried both to deploy the drivers in $CATALINA_HOME/lib and WEB-INF/lib, but still have the same problem.

Update:

It looks like the connection pool may NOT be the issue. If I use DBCP, I do not get errors about memory leaks, but if I run "Find Leaks" on the manager page, Tomcat definitely discovers a leak in the application - just from starting it, running an operation that reads from the database, then stopping it. If I just start/stop it, then no issue reported. I have made sure that all connections/statements/resultSets are properly closed. If I switch back to Tomcat JDBC, I still have the same issue, it just gets reported (at least as far as I can tell) during stop/restart of the application as [Pool-Cleaner] Thread not being able to be stopped, and the Manager finding leaks when clicking the "Find Leaks" button.

Upvotes: 3

Views: 4509

Answers (2)

kvgeorge1
kvgeorge1

Reputation: 33

Ok, discovered that this is NOT AT ALL related to JDBC (face-palm). Turns out this is an RMI issue, so I am now going to re-post this question as a new question.

Thanks everyone for your time.

Upvotes: 0

Andreas
Andreas

Reputation: 159215

Your JDBC drivers should be in $CATALINA_HOME/lib, and your database connection pools should be configured in the server.xml file using <Resource> tags. You context.xml file for the webapp should then link to the global data source with a <ResourceLink> tag.

This way connections are global and shared by all webapps connecting to the same database. Connections will not be released when a webapp is stopped or restarted, because they don't belong to the webapp, they belong to Tomcat.

No database connection memory leak, assuming all your webapp servlets/handlers clean up their resources correctly in finally blocks.

FYI: Deregistring a driver doesn't release any resources, such as open Connections, Statements, and ResultSets. It just prevents new connections from being created.

Upvotes: 2

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