How can I cancel a Task after a timeout?

Question

I have some Task execute a I/O blocking operation that can hang (fetching a file from an URL)

task = new Task<List<WSDLOperation>>() {
            @Override
            protected List<WSDLOperation> call() {
                List<WSDLOperation> services = new ArrayList<>();
                try {
                    services = WSDLService.createService(wsdlURL).getOperations();
                } catch (Exception ex) {
                    LOG.log(Level.WARNING, "Can't reach {0}", wsdlURL);
                }
                return services;
            }
        };

    }

The method createService can wait forever without throwing any Exception. (I execute the task using a global (static public)ExecutorService defined in Main class).

It looks like the problem is in createService method. Methods that can hang forever should throw interrupted exception, else it's hard to kill it (you can always call System.exit which is a bad practice - it kills the whole jvm ). Also see http://stackoverflow.com/questions/671049/how-do-you-kill-a-thread-in-java in case you haven't yet. — Viktor K., Jun 04 '14 at 01:37
`createService` is a third-part method, I have no control on it, is there any method to associate the `Task` with some timeout ? — Salah Eddine Taouririt, Jun 04 '14 at 01:44
`Future` might help you. See http://stackoverflow.com/questions/2275443/how-to-timeout-a-thread — zella, Jun 04 '14 at 02:14
It seems that the operation fires an `Exception` After a long timeout. — Salah Eddine Taouririt, Jun 04 '14 at 02:18

score 5 · Accepted Answer · answered Jun 04 '14 at 02:32

How use future and cancel task after timeout:

import java.util.concurrent.Callable;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;

public class Test {
    public static void main(String[] args) throws Exception {
        ExecutorService executor = Executors.newSingleThreadExecutor();
        Task t = new Task();
        Future<String> future = executor.submit(t);

        try {
            System.out.println("Started..");
            System.out.println(future.get(5, TimeUnit.SECONDS)); // throws
                                                                    // TimeoutException
            System.out.println("Finished!");
        } catch (TimeoutException e) {
            future.cancel(true);
            System.out.println("Terminated!");
        }
    }
}

class Task implements Callable<String> {
    @Override
    public String call() throws Exception {
        for (int i = 0; i < 1000; i++) {
            Thread.sleep(1000);
            System.out.println("task running!");
        }
        return "Ready!";
    }
}

Here the `future.cancel(true)` in `TimeoutException` handling part will just set the interrupt flag of future thread to `true` right? It wouldn't guarantee the future actually stops and kills the task in progress. — krackoder, Oct 31 '18 at 21:17

score -1 · Answer 2 · answered Jun 04 '14 at 02:19

-1

You are using ExecutorService, so you can do it after submitting the task:

ExecutorService executor = // ...  
Future<?> future = executor.submit(task);
future.get(5, TimeUnit.MINUTES); // timeout 5 mins

answered Jun 04 '14 at 02:19

Ilya

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That still won't kill the task itself. It just means the caller gives up on the blocking `get`. If `createService` is interruptible the caller could try `future.cancel(true)` but otherwise they're out of luck. – Thorn G Jun 04 '14 at 02:57
4

Calling `future.get` on the `javafx` thread will bock the UI. – Salah Eddine Taouririt Jun 04 '14 at 03:59

How can I cancel a Task after a timeout?

2 Answers2

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