Sunil's Notes: Memory Leak Servlet

I wanted to learn how to identify the Memory Leaks in WAS and how to analyze the problem using
1) The IBM Pattern modeling and Analysis tool for Java
2) IBM HeapAnalyzer tool

So i started by creating a sample MemoryLeakServlet like this.

public class MemoryLeakServlet extends HttpServlet {
 private static final long serialVersionUID = 1L;
     private static ArrayList st = new ArrayList();
  
     protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
     ArrayList st1 = new ArrayList();
     st1.add("This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string ");
     st1.add("This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string ");
     st1.add("This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string ");
     st1.add("This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string ");
     st1.add("This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string ");
     st1.add("This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string ");
     st1.add("This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string ");
     st1.add("This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string ");
     st1.add("This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string ");
     st1.add("This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string ");
     st1.add("This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string ");
     st1.add("This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string ");
     st1.add("This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string ");
     st1.add("This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string ");
     st1.add("This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string ");
     st1.add("This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string ");
     st1.add("This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string ");
     st1.add("This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string ");
     st1.add("This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string ");
     st1.add("This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string ");
     st1.add("This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string ");
     st1.add("This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string ");
     st1.add("This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string This is a big string ");
     System.out.println("Inside MemoryLeakServlet.doGet() " + st.size());
     
     st.add(st1);
     response.setContentType("text/html");
     response.getWriter().println("Hello from memory leak servlet");
 }

}
As you can see the MemoryLeakServlet has one static ArrayList st and i keep adding data to it for every HTTP GET request.

Once that was done i used JMEter to create a simple performance test which kept making HTTP GET requests to MemoryLeakServlet until i got OutOfMemory leak error and during that time i kept looking at native_stderr.log file using PAM tool to see what type of data i see
Memory Leak Servlet

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