CODEWITHSUNDEEP
javatomcatweb-applications
AL̲̳I
AL̲̳I

Reputation: 2461

Tomcat web application stops automatically

I have a dedicated server running CentOS 5.9, Apache-Tomcat 5.5.36. I have written a JAVA web applications which runs every minute to collect the data from multiple sensors. I am using ScheduledExecutorService to execute the threads. (one thread for each sensor every minute and there can be more than hundred sensors) The flow of the thread is

  1. Collect sensor information from the database.
  2. Sends the command to the instrument to collect data.
  3. Update the database with the data values.

There is another application that checks the database every minute and send the alerts to the users (if necessary). I have monitored the application using jvisualVM, I cant find any memory leak. for every thread. The applications work fine but after some time(24 Hour - 48 Hours) the applications stop working. I cant find out what the problem could be, is it server configuration problem, too many threads or what?

Does anyone have any idea what might be going wrong or is there anyone who has done think kind of work? Please help, Thanks

UPDATE : including code

public class Scheduler {
       private final ScheduledExecutorService scheduler = 
          Executors.newScheduledThreadPool(1);
       public void startProcess(int start) {
           final Runnable uploader = new Runnable() {
            @SuppressWarnings("rawtypes")
            public void run() 
            { 
                //Select data from the database
                ArrayList dataList = getData();
                for(int i=0;i<dataList.size();i++)
                {
                    String args = dataList.get(i).toString();
                    ExecutorThread comThread = new ExecutorThread(args...);
                    comThread.start();
                }
            }
        };
        scheduler.scheduleAtFixedRate(uploader, 0, 60 , TimeUnit.SECONDS);
       }
    }

public class ExecutorThread extends Thread {

    private variables...
    public CommunicationThread(args..)
    {
        //Initialise private variable
    }

    public void run()
    {
        //Collect data from sensor
        //Update Database
    }
}

Upvotes: 0

Views: 2683

Answers (2)

Boris the Spider
Boris the Spider

Reputation: 61128

Take heed of this innocuous line from the ScheduledExecutorService.schedule... Javadoc

If any execution of the task encounters an exception, subsequent executions are suppressed.

This means that if you are running into an Exception at some point and not handling it, the Exception will propagate into the ScheduledExecutorService and it will kill your task.

To avoid this problem you need to make sure the entire Runnable is wrapped in a try...catch and Exceptions are guaranteed to never be unhandled.

You can also extend the ScheduledExecutorService (also mentioned in the javadoc) to handle uncaught exceptions :-

final ScheduledExecutorService ses = new ScheduledThreadPoolExecutor(10){

    @Override
    protected void afterExecute(Runnable r, Throwable t) {
        super.afterExecute(r, t);
        if (t == null && r instanceof Future<?>) {
            try {
                Object result = ((Future<?>) r).get();
            } catch (CancellationException ce) {
                t = ce;
            } catch (ExecutionException ee) {
                t = ee.getCause();
            } catch (InterruptedException ie) {
                Thread.currentThread().interrupt(); // ignore/reset
            }
        }
        if (t != null) {
            System.out.println(t);
        }
    }
};

Here the afterExecute method simply System.out.printlns the Throwable but it could do other things. Alert users, restart tasks etc...

Upvotes: 1

user2256686
user2256686

Reputation: 245

Can't say much without a code, but you need to be sure that your thread always exits properly - doesn't hang in memory on any exception, closes connection to database, etc.

Also, for monitoring your application, you can take a thread dump every some period of time to see how many threads the application generates.

Another suggestion is configure Tomcat to take a heap dump on OutOfMemoryError. If that's an issue, you'll be able to analyze what is filling up the memory

Upvotes: 1

Related Questions