Servlet Monitoring with Metrics

Metrics from Coda Hale is a wonderful library to ease the monitoring of the performance of your code. It gives you tons of metrics directly via JMX, logs or CSV files.

I use it to monitor the performance of servlet in a JEE6 application. It is very simple to set up:

1. Add the following dependency to your pom.xml:

           
           
               com.yammer.metrics
               metrics-core
               2.2.0
           
   

2. Declare a Timer:

       /**
        * the timer for monitoring incoming HTTP POST requests.
        */
       private final Timer postTimer = Metrics.newTimer(getClass(), "post-requests-timer", TimeUnit.MILLISECONDS, TimeUnit.SECONDS);
   

   This code instantiates a new Timer where duration is measured in milliseconds and rate in seconds (to compute request per second).


3. Use the previous Timer when handling HTTP request:

       /**
        * Handles the HTTP
        * POST method.
        *
        * @param request servlet request
        * @param response servlet response
        * @throws ServletException if a servlet-specific error occurs
        * @throws IOException if an I/O error occurs
        */
       @Override
       protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
           // starts stopwatch
           final TimerContext context = postTimer.time();
   
           // handles request and response, calls business logic
           ...
   
           // ends stopwatch
           context.stop();
       }
   

4. Put some load on your servlet and monitor it using JConsole for instance: