Hi!
I'm working on a research about database performance and I'm running a TPC-W implementation (based on http://www.ece.wisc.edu/~pharm/tpcw.shtml) on some databases (Monet, MySQL, Postgresql).
Basically, what is being done is having some emulated browsers generating load on the servlet container (tomcat in my case) that access the database through JDBC.
-------------- -------------- ---------------- | Emulated | | Tomcat | | DB | | Browser | -----> | | ------> | | -------------- -------------- ----------------
When running this benchmark with concurrent accesses I'm getting problems. If I try 5 concurrent Emulated Browsers running (and 5 concurrent database connections) everything goes well. The problem starts when I increase the concurrency. With 30 concurrent connections everything goes well for a few minutes and then it stops working. The servlet container stops responding and monet uses low percentage of CPU on this state.
When I try to kill tomcat and start again (without killing Monet) it starts working again and stops after a while.
Based on this experiment it seems that Monet is still responsive, but the instance of servlet container that was accessing Monet just freezes.
I'm trying to investigate it a little more, but since I'm not an expert on MonetDB internals, I'd like to know if there is some known issue like this one or if anyone can have a tip on how to solve this.
Since Monet is responsive and the servlet container is freezing, it looks like JDBC driver is doing something that is freezing the container (I used to suspect on application, but since it is working very well with MySQL and Postgresql, it seems to not be the problem).
I'll appreciate any help on this subject.
Thanks very much for your attention.
Best regards, Anderson Supriano