Long running task in servlet

Hi,

I want to run some background job without blocking user's browser which I started in Thread.

here is my code snippet :

calling from controller :

/**
 * Running replace task in other thread
 * @param queueId
 * @param replaceSSN
 * @param createTask
 * @throws InterruptedException
 */
private void runReplaceTaskInThread(String queueId, String replaceSSN, boolean createTask) throws InterruptedException {
ReplaceTaskCmd replaceTaskCmd = new ReplaceTaskCmd(queueId,replaceSSN,createTask);
long waitTime = 100L; // Wait per step
boolean replaceTaskFinished = false ;
SalsaLogger.logTrace(this, "StartReplaceTask thread...");
Thread replaceTaskThread = new Thread(replaceTaskCmd,"ReplaceTask will run for "+replaceSSN);
    replaceTaskThread.start();
                      
                    // display a page to user after thread is started
    SalsaLogger.logTrace(this, "ReplaceTask threads started.");
    
    while(!replaceTaskFinished){
       if(replaceTaskCmd.isRunning()){
         replaceTaskFinished = false ;
       }else{
         replaceTaskFinished = true ;
         break ;  
       }
       Thread.sleep(waitTime);
    }
    SalsaLogger.logTrace(this, "End of replaceTaskThread...");
   // Stop threads
    replaceTaskThread = null;

}
 
 
run() method : 
 
public void run(){
isFinished = false;
try{
// run some background task

} catch(AutomationBackendException ae){
e = ae;
} catch (InvalidParameterException eI) {
e = eI ;
} finally  {
isFinished = true;
}
}

Now my problem is that thread is not sleeping and it blocks user's browser for ever ...

any help will be appriciated..

Thanks,
Rishi

[BSouther: Added UBB CODE tags]
[ March 05, 2008: Message edited by: Ben Souther ]

It looks as if this code will not terminate until "replaceTaskFinished" is set to true (which supposedly happens in replaceTaskThread). So you haven't really an independent thread here.

Also, if "replaceTaskFinished" is an instance variable, then this code is not thread-safe. Any write access to instance variables needs to be synchronized. But, as pointed out above, the code should not wait for it to become true to begin with.

Hardly surprising since (as near as I can tell) you are holding on to the thread that is handling the request that started the whole thing. You should let that request terminate normally with something like a "working" HTML page and find another way to update the user. There have been a lot of discussions of this sort of thing on the ranch so do some searches.

Bill

Thanks for all the replies...

I got what you both are saying ...How about setting ReplaceTask Thread as daemon thread will that work ?

replaceTaskThread.setDaemon(true):
replaceTaskThread.start():

Do you think daemon thread will garbage collected by web container any idea on performance how will it affect ?

On my site, I have a simple demo app that does something similar.
http://simple.souther.us/not-so-simple.html

Look for LongRunningProcess.
It might be enough to get you going in the right direction.

Thanks for all the help...It helped a lot

Rishi