Effective Debugging of Memory Leaks in Ruby

Recently at work I was tasked with finding a memory leak in a legacy Ruby application I was unfamiliar with. We had been monitoring the application’s memory usage for several weeks and it was clear that there was a slow memory leak somewhere in the application. When I began to look at the source code I realized it I didn’t know where to begin looking for the memory leak. The application was using a framework and several gems that I was unfamiliar with and was structured different than other Ruby projects I had been working on. I also found that I really missed Erlang’s excellent runtime_tools that I rely on for diagnosing issues in Erlang applications. After a lot of trial and error I finally found and fixed the memory leak. In this blog post I share the steps I devised to find the memory leak in the unfamiliar source code.