Blogging Roller

I tried the kill -QUIT trick on FreeRoller this afternoon after it locked up. Looking at the stack traces for Tomcat's 75 threads, I found that most were either waiting for database connections or involved reading cache entries from the disk.

Recently, I had changed to OSCache settings so that Roller caches to disk rather than to memory. I did that because Roller was running out of memory. Caching to disk fixed the out-of-memory problem, but at the expense of heavy disk access. So, I changed the OSCache settings back to cache to both disk and to memory. OSCache seems to have some limitations in this area. Apparently, if you configure OSCache to cache in memory and to disk, you can limit the number of entries in the memory cache, but the disk cache is unlimited - which is not the best situation.

Also, I changed the DBCP connection pooling parameters to reduce the maxIdle and maxWait so that threads will timeout quickly rather than hanging around waiting for connections and thus forcing the creation of new threads.

Those changes kept FreeRoller up for a much longer period of time, but did not fix the problem.