How to timeout a thread

Question

I want to run a thread for some fixed amount of time  If it is not completed within that time  I want to either kill it  throw some exception  or handle it in some way  How can it be done   One way of doing it as I figured out from this thread is to use a TimerTask inside the run   method of the Thread   Are there any better solutions for this    nbsp  EDIT  Adding a bounty as I needed a clearer answer  The ExecutorService code given below does not address my problem  Why should I sleep   after executing  some code - I have no handle over this piece of code   If the code is completed and the sleep   is interrupted  how can that be a timeOut   The task that needs to be executed is not in my control  It can be any piece of code  The problem is this piece of code might run into an infinite loop  I don t want that to happen  So  I just want to run that task in a separate thread  The parent thread has to wait till that thread finishes and needs to know the status of the task  i e whether it timed out or some exception occured or if its a success   If the task goes into an infinite loop  my parent thread keeps on waiting indefinitely  which is not an ideal situation

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One thing that I ve not seen mentioned is that killing threads is generally a Bad Idea   There are techniques for making threaded methods cleanly abortable  but that s different to just killing a thread after a timeout   The risk with what you re suggesting is that you probably don t know what state the thread will be in when you kill it - so you risk introducing instability  A better solution is to make sure your threaded code either doesn t hang itself  or will respond nicely to an abort request

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Great answer by BalusC s      but Just to add that the timeout itself does not interrupt the thread itself  even if you are checking with while  Thread interrupted    in your task  if you want to make sure thread is stopped you should also make sure future cancel   is invoked when timeout exception is catch   package com stackoverflow q2275443    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            Future lt String gt  future   executor submit new Task              try                System out println  Started                  System out println future get 3  TimeUnit SECONDS                System out println  Finished               catch  TimeoutException e                  Without the below cancel the thread will continue to live                 even though the timeout exception thrown              future cancel                System out println  Terminated                         executor shutdownNow               class Task implements Callable lt String gt         Override      public String call   throws Exception         while  Thread currentThread isInterrupted               System out println  Im still running baby

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Assuming the thread code is out of your control   From the Java documentation mentioned above      What if a thread doesn t respond to Thread interrupt       In some cases  you can use application specific tricks  For example    if a thread is waiting on a known socket  you can close the socket to   cause the thread to return immediately  Unfortunately  there really   isn t any technique that works in general  It should be noted that in   all situations where a waiting thread doesn t respond to   Thread interrupt  it wouldn t respond to Thread stop either  Such   cases include deliberate denial-of-service attacks  and I O operations   for which thread stop and thread interrupt do not work properly    Bottom Line   Make sure all threads can be interrupted  or else you need specific knowledge of the thread - like having a flag to set  Maybe you can require that the task be given to you along with the code needed to stop it - define an interface with a stop   method  You can also warn when you failed to stop a task

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I was looking for an ExecutorService that can interrupt all timed out Runnables executed by it  but found none  After a few hours I created one as below  This class can be modified to enhance robustness   public class TimedExecutorService extends ThreadPoolExecutor       long timeout      public TimedExecutorService int numThreads  long timeout  TimeUnit unit            super numThreads  numThreads  0L  TimeUnit MILLISECONDS  new ArrayBlockingQueue lt Runnable gt  numThreads   1            this timeout   unit toMillis timeout               Override     protected void beforeExecute Thread thread  Runnable runnable            Thread interruptionThread   new Thread new Runnable                  Override             public void run                     try                          Wait until timeout and interrupt this thread                     Thread sleep timeout                       System out println  The runnable times out                         thread interrupt                      catch  InterruptedException e                        e printStackTrace                                                        interruptionThread start              Usage   public static void main String   args         Runnable abcdRunnable   new Runnable              Override         public void run                 System out println  abcdRunnable started                try                   Thread sleep 20000                 catch  InterruptedException e                       logger info  The runnable times out                               System out println  abcdRunnable ended                          Runnable xyzwRunnable   new Runnable              Override         public void run                 System out println  xyzwRunnable started                try                   Thread sleep 20000                 catch  InterruptedException e                       logger info  The runnable times out                               System out println  xyzwRunnable ended                          int numThreads   2  timeout   5      ExecutorService timedExecutor   new TimedExecutorService numThreads  timeout  TimeUnit SECONDS       timedExecutor execute abcdRunnable       timedExecutor execute xyzwRunnable       timedExecutor shutdown

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In the solution given by BalusC  the main thread will stay blocked for the timeout period  If you have a thread pool with more than one thread  you will need the same number of additional thread that will be using Future get long timeout TimeUnit unit  blocking call to wait and close the thread if it exceeds the timeout period    A generic solution to this problem is to create a ThreadPoolExecutor Decorator that can add the timeout functionality  This Decorator class should create as many threads as ThreadPoolExecutor has  and all these threads should be used only to wait and close the ThreadPoolExecutor   The generic class should be implemented like below   import java util List  import java util concurrent     public class TimeoutThreadPoolDecorator extends ThreadPoolExecutor         private final ThreadPoolExecutor commandThreadpool      private final long timeout      private final TimeUnit unit       public TimeoutThreadPoolDecorator ThreadPoolExecutor threadpool                                        long timeout                                        TimeUnit unit            super   threadpool getCorePoolSize                    threadpool getMaximumPoolSize                    threadpool getKeepAliveTime TimeUnit MILLISECONDS                   TimeUnit MILLISECONDS                  threadpool getQueue              this commandThreadpool   threadpool          this timeout timeout          this unit unit              Override     public void execute Runnable command            super execute    - gt                Future lt   gt  future   commandThreadpool submit command               try                   future get timeout  unit                 catch  InterruptedException e                    Thread currentThread   interrupt                  catch  ExecutionException   TimeoutException e                    throw new RejectedExecutionException e                 finally                   future cancel true                                         Override     public void setCorePoolSize int corePoolSize            super setCorePoolSize corePoolSize           commandThreadpool setCorePoolSize corePoolSize               Override     public void setThreadFactory ThreadFactory threadFactory            super setThreadFactory threadFactory           commandThreadpool setThreadFactory threadFactory               Override     public void setMaximumPoolSize int maximumPoolSize            super setMaximumPoolSize maximumPoolSize           commandThreadpool setMaximumPoolSize maximumPoolSize               Override     public void setKeepAliveTime long time  TimeUnit unit            super setKeepAliveTime time  unit           commandThreadpool setKeepAliveTime time  unit               Override     public void setRejectedExecutionHandler RejectedExecutionHandler handler            super setRejectedExecutionHandler handler           commandThreadpool setRejectedExecutionHandler handler               Override     public List lt Runnable gt  shutdownNow             List lt Runnable gt  taskList   super shutdownNow            taskList addAll commandThreadpool shutdownNow             return taskList              Override     public void shutdown             super shutdown            commandThreadpool shutdown              The above decorator can be used as below   import java util concurrent SynchronousQueue  import java util concurrent ThreadPoolExecutor  import java util concurrent TimeUnit   public class Main        public static void main String   args            long timeout   2000           ThreadPoolExecutor threadPool   new ThreadPoolExecutor 3  10  0  TimeUnit MILLISECONDS  new SynchronousQueue lt  gt  true             threadPool   new TimeoutThreadPoolDecorator  threadPool                   timeout                  TimeUnit MILLISECONDS             threadPool execute command 1000            threadPool execute command 1500            threadPool execute command 2100            threadPool execute command 2001             while threadPool getActiveCount   gt 0           threadPool shutdown                 private static Runnable command int i             return    - gt                System out println  Running Thread   Thread currentThread   getName                 System out println  Starting command with sleep   i               try                   Thread sleep i                 catch  InterruptedException e                    System out println  Thread   Thread currentThread   getName     with sleep of   i   is Interrupted                       return                            System out println  Completing Thread   Thread currentThread   getName     after sleep of   i

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Here is my really simple to use helper class to run or call piece of Java code  -   This is based on the excellent answer from BalusC    package com mycompany util concurrent   import java util concurrent Callable  import java util concurrent ExecutionException  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          Calling   link Callable call    or Running   link Runnable run    code    with a timeout based on   link Future get long  TimeUnit        author pascaldalfarra        public class CallableHelper        private CallableHelper                    public static final void run final Runnable runnable  int timeoutInSeconds                run runnable  null  timeoutInSeconds              public static final void run final Runnable runnable  Runnable timeoutCallback  int timeoutInSeconds                call new Callable lt Void gt                           Override             public Void call   throws Exception                               runnable run                    return null                           timeoutCallback  timeoutInSeconds               public static final  lt T gt  T call final Callable lt T gt  callable  int timeoutInSeconds                return call callable  null  timeoutInSeconds               public static final  lt T gt  T call final Callable lt T gt  callable  Runnable timeoutCallback  int timeoutInSeconds                ExecutorService executor   Executors newSingleThreadExecutor            try                       Future lt T gt  future   executor submit callable               T result   future get timeoutInSeconds  TimeUnit SECONDS               System out println  CallableHelper - Finished                 return result                    catch  TimeoutException e                        System out println  CallableHelper - TimeoutException                 if timeoutCallback    null                                timeoutCallback run                                    catch  InterruptedException e                        e printStackTrace                      catch  ExecutionException e                        e printStackTrace                      finally                       executor shutdownNow                executor   null                     return null

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I think you should take a look at proper concurrency handling mechanisms  threads running into infinite loops doesn t sound good per se  btw   Make sure you read a little about the  killing  or  stopping  Threads topic   What you are describing sound very much like a  rendezvous   so you may want to take a look at the CyclicBarrier   There may be other constructs  like using CountDownLatch for example  that can resolve your problem  one thread waiting with a timeout for the latch  the other should count down the latch if it has done it s work  which would release your first thread either after a timeout or when the latch countdown is invoked    I usually recommend two books in this area  Concurrent Programming in Java and Java Concurrency in Practice

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BalusC said      Update  to clarify a conceptual misunderstanding  the sleep   is not required  It is just used for SSCCE demonstration purposes  Just do your long running task right there in place of sleep      But if you replace Thread sleep 4000   with for  int i   0  i  lt  5E8  i       then it doesn t compile  because the empty loop doesn t throw an InterruptedException   And for the thread to be interruptible  it needs to throw an InterruptedException    This seems like a serious problem to me  I can t see how to adapt this answer to work with a general long-running task    Edited to add  I reasked this as a new question    interrupting a thread after fixed time  does it have to throw InterruptedException

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Indeed rather use ExecutorService instead of Timer  here s an SSCCE   package com stackoverflow q2275443   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            Future lt String gt  future   executor submit new Task              try               System out println  Started                  System out println future get 3  TimeUnit SECONDS                System out println  Finished               catch  TimeoutException e                future cancel true               System out println  Terminated                        executor shutdownNow             class Task implements Callable lt String gt         Override     public String call   throws Exception           Thread sleep 4000      Just to demo a long running task of 4 seconds          return  Ready              Play a bit with the timeout argument in Future get   method  e g  increase it to 5 and you ll see that the thread finishes  You can intercept the timeout in the catch  TimeoutException e  block   Update  to clarify a conceptual misunderstanding  the sleep   is not required  It is just used for SSCCE demonstration purposes  Just do your long running task right there in place of sleep    Inside your long running task  you should be checking if the thread is not interrupted as follows   while   Thread interrupted             Do your long running task here

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I created a helper class just for this some time ago  Works great    import java util concurrent BrokenBarrierException  import java util concurrent CyclicBarrier         TimeOut class - used for stopping a thread that is taking too long     author Peter Goransson        public class TimeOut        Thread interrupter      Thread target      long timeout      boolean success      boolean forceStop       CyclicBarrier barrier                           param target The Runnable target to be executed         param timeout The time in milliseconds before target will be interrupted or stopped         param forceStop If true  will Thread stop   this target instead of just interrupt                public TimeOut Runnable target  long timeout  boolean forceStop                  this timeout   timeout          this forceStop   forceStop           this target   new Thread target                  this interrupter   new Thread new Interrupter              barrier   new CyclicBarrier 2      There will always be just 2 threads waiting on this barrier            public boolean execute   throws InterruptedException                 Start target and interrupter         target start            interrupter start                Wait for target to finish or be interrupted by interrupter         target join               interrupter interrupt       stop the interrupter             try               barrier await       Need to wait on this barrier to make sure status is set           catch  BrokenBarrierException e                   Something horrible happened  assume we failed             success   false                      return success     status is set in the Interrupter inner class            private class Interrupter implements Runnable            Interrupter               public void run                 try                   Thread sleep timeout      Wait for timeout period and then kill this target                 if  forceStop                      target stop       Need to use stop instead of interrupt since we re trying to kill this thread                                   else                       target interrupt       Gracefully interrupt the waiting thread                                   System out println  done                                 success   false                catch  InterruptedException e                    success   true                              try                   barrier await       Need to wait on this barrier               catch  InterruptedException e                       If the Child and Interrupter finish at the exact same millisecond we ll get here                    In this weird case assume it failed                 success   false                                             catch  BrokenBarrierException e                       Something horrible happened  assume we failed                 success   false                                      It is called like this   long timeout   10000     number of milliseconds before timeout TimeOut t   new TimeOut new PhotoProcessor filePath  params   timeout  true   try                            boolean sucess   t execute       Will return false if this times out   if   sucess           This thread timed out       else          This thread ran completely and did not timeout       catch  InterruptedException e

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I post you a piece of code which show a way how to solve the problem  As exemple I m reading a file  You could use this method for another operation  but you need to implements the kill   method so that the main operation will be interrupted   hope it helps   import java io File  import java io FileInputStream  import java io FileNotFoundException  import java io IOException  import java io InputStream          Main class         author el         public class Main                  Thread which perform the task which should be timed out                  author el                     public static class MainThread extends Thread                          For example reading a file  File to read                      final private File fileToRead                         InputStream from the file                      final private InputStream myInputStream                         Thread for timeout                      final private TimeOutThread timeOutThread                          true if the thread has not ended                      boolean isRunning   true                          true if all tasks where done                      boolean everythingDone   false                          if every thing could not be done  an   link Exception  may have            Happens                      Throwable endedWithException   null                          Constructor                          param file             throws FileNotFoundException                     MainThread File file  throws FileNotFoundException               setDaemon false               fileToRead   file                 open the file stream              myInputStream   new FileInputStream fileToRead                  Instantiate the timeout thread              timeOutThread   new TimeOutThread 10000  this                                     Used by the   link TimeOutThread                       public void kill                 if  isRunning                    isRunning   false                  if  myInputStream    null                        try                              close the stream  it may be the problem                          myInputStream close                          catch  IOException e                               Not interesting                         System out println e toString                                                             synchronized  this                        notify                                                                      The task which should be timed out                       Override         public void run                 timeOutThread start                int bytes   0              try                      do something                 while  myInputStream read      0                           may block the thread                      myInputStream read                        bytes                           simulate a slow stream                      synchronized  this                            wait 10                                                           everythingDone   true                catch  IOException e                    endedWithException   e                catch  InterruptedException e                    endedWithException   e                finally                   timeOutThread kill                    System out println  -- read     bytes     bytes                     isRunning   false                  synchronized  this                        notifyAll                                                                    Timeout Thread  Kill the main task if necessary                  author el                     public static class TimeOutThread extends Thread           final long timeout          final MainThread controlledObj           TimeOutThread long timeout  MainThread controlledObj                setDaemon true               this timeout   timeout              this controlledObj   controlledObj                     boolean isRunning   true                          If we done need the   link TimeOutThread  thread  we may kill it                      public void kill                 isRunning   false              synchronized  this                    notify                                                                          Override         public void run                 long deltaT   0l              try                   long start   System currentTimeMillis                    while  isRunning    deltaT  lt  timeout                        synchronized  this                            wait Math max 100  timeout - deltaT                                              deltaT   System currentTimeMillis   - start                                  catch  InterruptedException e                       If the thread is interrupted                     you may not want to kill the main thread                     but probably yes                finally                   isRunning   false                            controlledObj kill                                    Start the main task and wait for the end                  param args         throws FileNotFoundException             public static void main String   args  throws FileNotFoundException           long start   System currentTimeMillis            MainThread main   new MainThread new File args 0             main start            try               while  main isRunning                    synchronized  main                        main wait 1000                                               long stop   System currentTimeMillis                 if  main everythingDone                  System out println  all done in      stop - start      ms                 else                   System out println  could not do everything in                              stop - start      ms                     if  main endedWithException    null                      main endedWithException printStackTrace                            catch  InterruptedException e                System out println  You ve killed me                         Regards

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There isn t a 100  reliable way to do this for any old task  The task has to be written with this ability in mind   Core Java libraries like ExecutorService cancel asynchronous tasks with interrupt   calls on the worker thread  So  for example  if the task contains some sort of loop  you should be checking its interrupt status on each iteration  If the task is doing I O operations  they should be interruptible too mdash and setting that up can be tricky  In any case  keep in mind that code has to actively check for interrupts  setting an interrupt doesn t necessarily do anything   Of course  if your task is some simple loop  you can just check the current time at each iteration and give up when a specified timeout has elapsed  A worker thread isn t needed in that case

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Now   l meet a issue like this  It happens to decode picture  The process of decode takes too much time that the screen keep black  l add a time controler  when the time is too long  then pop up from the current Thread  The following is the diff      ExecutorService executor   Executors newSingleThreadExecutor       Future lt Bitmap gt  future   executor submit new Callable lt Bitmap gt              Override        public Bitmap call   throws Exception          Bitmap bitmap   decodeAndScaleBitmapFromStream context  inputUri     do some time consuming operation        return null                                  try              Bitmap result   future get 1  TimeUnit SECONDS            catch  TimeoutException e              future cancel true                   executor shutdown           return  bitmap   null

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I had the same problem  So i came up with a simple solution like this    public class TimeoutBlock     private final long timeoutMilliSeconds      private long timeoutInteval 100       public TimeoutBlock long timeoutMilliSeconds           this timeoutMilliSeconds timeoutMilliSeconds             public void addBlock Runnable runnable  throws Throwable          long collectIntervals 0          Thread timeoutWorker new Thread runnable           timeoutWorker start            do               if collectIntervals gt  this timeoutMilliSeconds                   timeoutWorker stop                    throw new Exception   lt  lt  lt  lt  lt  lt  lt  lt  lt  lt      gt  gt  gt  gt  gt  gt  gt  gt  gt  gt  gt  Timeout Block Execution Time Exceeded In   timeoutMilliSeconds   Milli Seconds  Thread Block Terminated                               collectIntervals  timeoutInteval                         Thread sleep timeoutInteval             while timeoutWorker isAlive             System out println   lt  lt  lt  lt  lt  lt  lt  lt  lt  lt      gt  gt  gt  gt  gt  gt  gt  gt  gt  gt  gt  Timeout Block Executed Within   collectIntervals   Milli Seconds                            return the timeoutInteval             public long getTimeoutInteval             return timeoutInteval                         param timeoutInteval the timeoutInteval to set             public void setTimeoutInteval long timeoutInteval            this timeoutInteval   timeoutInteval            Guarantees that if block didn t execute within the time limit  the process will terminate and throws an exception   example    try           TimeoutBlock timeoutBlock   new TimeoutBlock 10   60   1000    set timeout in milliseconds         Runnable block new Runnable                   Override             public void run                       TO DO write block of code                                    timeoutBlock addBlock block     execute the runnable block         catch  Throwable e              catch the exception here   Which is block didn t execute within the time limit

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The following snippet will start an operation in a separate thread  then wait for up to 10 seconds for the operation to complete  If the operation does not complete in time  the code will attempt to cancel the operation  then continue on its merry way  Even if the operation cannot be cancelled easily  the parent thread will not wait for the child thread to terminate   ExecutorService executorService   getExecutorService    Future lt SomeClass gt  future   executorService submit new Callable lt SomeClass gt          public SomeClass call                Perform long-running task  return result  The code should check            interrupt status regularly  to facilitate cancellation            try          Real life code should define the timeout as a constant or        retrieve it from configuration     SomeClass result   future get 10  TimeUnit SECONDS          Do something with the result   catch  TimeoutException e        future cancel true          Perform other error handling  e g  logging  throwing an exception     The getExecutorService   method can be implemented in a number of ways  If you do not have any particular requirements  you can simply call Executors newCachedThreadPool   for thread pooling with no upper limit on the number of threads

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Consider using an instance of ExecutorService   Both invokeAll   and invokeAny   methods are available with a timeout parameter     The current thread will block until the method completes  not sure if this is desirable  either because the task s  completed normally or the timeout was reached   You can inspect the returned Future s  to determine what happened

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I think the answer mainly depends on the task itself    Is it doing one task over and over again   Is it necessary that the timeout interrupts a currently running task immediately after it expires    If the first answer is yes and the second is no  you could keep it as simple as this   public class Main        private static final class TimeoutTask extends Thread           private final long  timeoutMs          private Runnable  runnable           private TimeoutTask long timeoutMs  Runnable runnable                 timeoutMs   timeoutMs               runnable   runnable                      Override         public void run                 long start   System currentTimeMillis                while  System currentTimeMillis    lt   start    timeoutMs                      runnable run                              System out println  execution took      System currentTimeMillis   - start     ms                          public static void main String   args  throws Exception           new TimeoutTask 2000L  new Runnable                   Override             public void run                     System out println  doing something                        try                          pretend it s taking somewhat longer than it really does                     Thread sleep 100                     catch  InterruptedException e                        throw new RuntimeException e                                              start              If this isn t an option  please narrow your requirements - or show some code

[java] How to timeout a thread

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