Issue with executor thread pool

[sachin yadav]

Hi All,

I am using following code to create a thread pool using java executor framework.

public class Executor {	

	private static ExecutorService executor = null;	
	public static void main(String args[])	{
		
		executor = Executors.newFixedThreadPool(2);
		List<Future<String>> resultLlist = new ArrayList<Future<String>>();
		Queue<Runnable> activeTasks = null;
		Future<String> response = null;
		for(int i=0;i<1;i++)	{
			Callable<String> worker = new Worker();
			response = executor.submit(worker);
			resultLlist.add(response);			
		}
		executor.shutdown();
		try	{
			int executorWaitingTime = new Integer(10);
		if (!executor.awaitTermination(executorWaitingTime, TimeUnit.SECONDS))	{
			System.out.println("Executor did not shut down properly, forcing shutdown now");
			executor.shutdownNow();
			if(!executor.isTerminated())	{

			// problem -- need some way to kill threads here. Debug still shows Thread [pool-1-thread-1] (Running) which means thread is still running
								
			}
		}
	   } catch (InterruptedException ie) {
		   executor.shutdownNow();
	   }
		System.out.println("Future job is done!!");
		
	}
}

public class Worker implements Callable<String>{
	
	static long time = 10; 
	public String call() throws Exception {		
		for(;;)	{
			System.out.println("i will run forever");
		}
	}

}

the problem here is i need a way to forcefully clean all the threads spawned by executor thread pool. I understand that shutdownNow() will not work because thread is still actively running, but i wanted to get rid of thread if it doesn't return in some specified time.

[sachin yadav]

Ok, found a solution but don't know how good this is -

I have put responsibility on worker thread to check if it has got interrupted or not. This will make sure that if shutdownNow() is called which eventually interrupt the thread then work will stop working.

public class Worker implements Callable<String>{
	
	@SuppressWarnings("deprecation")
	public String call() throws Exception {		
		int i=0;
		for(;;)	{
			if (!Thread.currentThread().isInterrupted()) {
				System.out.println("i : "+ i++);
			}	else	{
				System.out.println(Thread.currentThread().getName()+" Is going to die");
				Thread.currentThread().stop();
			}
		}
	}
}

This works fine each time i run but to my surprise if i run in debug mode i can see wearied behavior. Some thread always left as in running mode even though log "is going to die" has got printed for all the running threads.

Any thoughts? How safe is it to implement this code?

[Paul Clapham]

Not safe at all. Read the API documentation for java.lang.Thread, in particular the documentation for the stop() method.

[sachin yadav]

Ya paul i know it's not safe and due to multiple complications with Stop method this was deprecated but what could be the alternative then? I have to forcefully kill thread in Executor thread pool incase they do not stop processing in fixed time.

[Paul Clapham]

You might want to consider reading this article. By the way it was high up in the list of links returned by Google when I used the keywords "java thread stop". You'll find other similar articles if you use those keywords; I suggest you read some of those as well.