Beautiful Testing

The Memory Leak That Wasn’t

It was almost two months after the “OK, but what’s a performance test?” episode before we were ready to start ramping up load with a reasonably complete system usage model on the eVersity project. The single-user and 10-user tests on this particular build had achieved better than required performance, so I prepared and ran a 100-user test. Since it was the first run of multiple usage scenarios at the same time, I made a point to observe the test and check the few server statistics that I had access to while the test was running.

The test ran for about an hour, and everything seemed fine until I looked at the scatter chart, which showed that all the pages that accessed the application server started slowing down about 10 minutes into the test and kept getting slower until the test ended. I surfed the site manually and it was fine. I checked the logfiles from the load generation tool to verify that I wasn’t seeing the effect of some kind of scripting error. Confident that it wasn’t something on my end, I ran the test again, only this time I used the site manually while the test was running. After about 15 minutes, I noticed those pages getting slow. I picked up the phone and called Sam, the architect for the project, to tell him that he had a memory leak on the application server.

Sam asked if I was running the test right then. I told him I was. I heard him clicking on his keyboard. He asked if the test was still running. I told him it was. He said, “Nope, ...