Java set timeout on a certain block of code

Question

Is it possible to force Java to throw an Exception after some block of code runs longer than acceptable

User · Answer

There is a hacky way to do it   Set some boolean field to indicate whether the work was completed  Then before the block of code  set a timer to run a piece of code after your timeout  The timer will check if the block of code had finished executing  and if not  throw an exception  Otherwise it will do nothing   The end of the block of code should  of course  set the field to true to indicate the work was done

User · Answer

EDIT  Peter Lawrey is completely right  it s not as simple as interrupting a thread  my original suggestion   and Executors  amp  Callables are very useful      Rather than interrupting threads  you could set a variable on the Callable once the timeout is reached  The callable should check this variable at appropriate points in task execution  to know when to stop   Callables return Futures  with which you can specify a timeout when you try to  get  the future s result  Something like this   try      future get timeoutSeconds  TimeUnit SECONDS    catch InterruptedException e       myCallable setStopMeAtAppropriatePlace true       See Future get  Executors  and Callable      https   docs oracle com javase 8 docs api java util concurrent Future html get-long-java util concurrent TimeUnit-  https   docs oracle com javase 8 docs api java util concurrent Callable html  https   docs oracle com javase 8 docs api java util concurrent Executors html newFixedThreadPool 28int 29

User · Answer

If you want a CompletableFuture way you could have a method like  public MyResponseObject retrieveDataFromEndpoint         CompletableFuture lt MyResponseObject gt  endpointCall           CompletableFuture supplyAsync    - gt               yourRestService callEnpoint withArg1  withArg2        try          return endpointCall get 10  TimeUnit MINUTES        catch  TimeoutException                   InterruptedException                   ExecutionException e           throw new RuntimeException  Unable to fetch data   e            If you re using spring  you could annotate the method with a  Retryable so that it retries the method three times if an exception is thrown

User · Answer

I faced a similar kind of issue where my task was to push a message to SQS within a particular timeout  I used the trivial logic of executing it via another thread and waiting on its future object by specifying the timeout  This would give me a TIMEOUT exception in case of timeouts    final Future lt ISendMessageResult gt  future    timeoutHelperThreadPool getExecutor   submit    - gt      return getQueueStore   sendMessage request  get        try     sendMessageResult   future get 200  TimeUnit MILLISECONDS     logger info  SQS PUSH SUCCESSFUL      return true     catch  final TimeoutException e      logger error  SQS PUSH TIMEOUT EXCEPTION        But there are cases where you can t stop the code being executed by another thread and you get true negatives in that case    For example - In my case  my request reached SQS and while the message was being pushed  my code logic encountered the specified timeout  Now in reality my message was pushed into the Queue but my main thread assumed it to be failed because of the TIMEOUT exception  This is a type of problem which can be avoided rather than being solved  Like in my case I avoided it by providing a timeout which would suffice in nearly all of the cases    If the code you want to interrupt is within you application and is not something like an API call then you can simply use   future cancel true    However do remember that java docs says that it does guarantee that the execution will be blocked    Attempts to cancel execution of this task  This attempt will fail if the task has already completed  has already been cancelled or could not be cancelled for some other reason  If successful and this task has not started when cancel is called this task should never run  If the task has already started then the mayInterruptIfRunning parameter determines whether the thread executing this task should be interrupted inan attempt to stop the task

User · Answer

Here s the simplest way that I know of to do this   final Runnable stuffToDo   new Thread        Override    public void run             Do stuff here              final ExecutorService executor   Executors newSingleThreadExecutor    final Future future   executor submit stuffToDo   executor shutdown       This does not cancel the already-scheduled task   try      future get 5  TimeUnit MINUTES      catch  InterruptedException ie          Handle the interruption  Or ignore it        catch  ExecutionException ee          Handle the error  Or ignore it        catch  TimeoutException te          Handle the timeout  Or ignore it        if   executor isTerminated        executor shutdownNow       If you want to stop the code that hasn t finished    Alternatively  you can create a TimeLimitedCodeBlock class to wrap this functionality  and then you can use it wherever you need it as follows   new TimeLimitedCodeBlock 5  TimeUnit MINUTES     Override public void codeBlock            Do stuff here     run

User · Answer

I can suggest two options    Within the method  assuming it is looping and not waiting for an external event  add a local field and test the time each time around the loop   void method         long endTimeMillis   System currentTimeMillis     10000      while  true               method logic         if  System currentTimeMillis    gt  endTimeMillis                   do some clean-up             return                     Run the method in a thread  and have the caller count to 10 seconds   Thread thread   new Thread new Runnable              Override         public void run                 method                  thread start    long endTimeMillis   System currentTimeMillis     10000  while  thread isAlive          if  System currentTimeMillis    gt  endTimeMillis               set an error flag         break            try           Thread sleep 500             catch  InterruptedException t          The drawback to this approach is that method   cannot return a value directly  it must update an instance field to return its value

User · Answer

I compiled some of the other answers into a single utility method   public class TimeLimitedCodeBlock      public static void runWithTimeout final Runnable runnable  long timeout  TimeUnit timeUnit  throws Exception       runWithTimeout new Callable lt Object gt             Override       public Object call   throws Exception           runnable run            return null                 timeout  timeUnit          public static  lt T gt  T runWithTimeout Callable lt T gt  callable  long timeout  TimeUnit timeUnit  throws Exception       final ExecutorService executor   Executors newSingleThreadExecutor        final Future lt T gt  future   executor submit callable       executor shutdown       This does not cancel the already-scheduled task      try         return future get timeout  timeUnit             catch  TimeoutException e            remove this if you do not want to cancel the job in progress         or set the argument to  false  if you do not want to interrupt the thread       future cancel true         throw e            catch  ExecutionException e            unwrap the root cause       Throwable t   e getCause          if  t instanceof Error            throw  Error  t          else if  t instanceof Exception            throw  Exception  t          else           throw new IllegalStateException t                          Sample code making use of this utility method     public static void main String   args  throws Exception       final long startTime   System currentTimeMillis        log startTime   calling runWithTimeout         try         TimeLimitedCodeBlock runWithTimeout new Runnable              Override         public void run               try               log startTime   starting sleep                 Thread sleep 10000               log startTime   woke up                           catch  InterruptedException e                log startTime   was interrupted                                    5  TimeUnit SECONDS             catch  TimeoutException e          log startTime   got timeout               log startTime   end of main method            private static void log long startTime  String msg        long elapsedSeconds    System currentTimeMillis   - startTime       System out format   1 5sms   2 16s   3 s n   elapsedSeconds  Thread currentThread   getName    msg         Output from running the sample code on my machine       0ms              main  calling runWithTimeout     13ms   pool-1-thread-1  starting sleep   5015ms              main  got timeout   5016ms              main  end of main method   5015ms   pool-1-thread-1  was interrupted

User · Answer

Yes  but its generally a very bad idea to force another thread to interrupt on a random line of code  You would only do this if you intend to shutdown the process   What you can do is to use Thread interrupt   for a task after a certain amount of time   However  unless the code checks for this it won t work  An ExecutorService can make this easier with Future cancel true   Its much better for the code to time itself and stop when it needs to

User · Answer

I created a very simple solution without using any frameworks or APIs  This looks more elegant and understandable  The class is called TimeoutBlock   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            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 to execute                                   timeoutBlock addBlock block     execute the runnable block         catch  Throwable e              catch the exception here   Which is block didn t execute within the time limit         This was so much useful for me when i had to connect to a FTP account  Then download and upload stuff  sometimes FTP connection hangs or totally breaks  This caused whole system to go down  and i needed a way to detect it and prevent it from happening   So i created this and used it  Works pretty well

User · Answer

Instead of having the task in the new thread and the timer in the main thread  have the timer in the new thread and the task in the main thread   public static class TimeOut implements Runnable      public void run             Thread sleep 10000           if taskComplete   false                System out println  Timed Out                return                    else               return                    public static boolean taskComplete   false  public static void main String   args        TimeOut timeOut   new TimeOut        Thread timeOutThread   new Thread timeOut       timeOutThread start          task starts here       task completed     taskComplete  true      while true     do all other stuff

User · Answer

If it is test code you want to time  then you can use the time attribute    Test timeout   1000    public void shouldTakeASecondOrLess         If it is production code  there is no simple mechanism  and which solution you use depends upon whether you can alter the code to be timed or not   If you can change the code being timed  then a simple approach is is to have your timed code remember it s start time  and periodically the current time against this  E g   long startTime   System currentTimeMillis          do stuff    long elapsed   System currentTimeMillis  -startTime  if  elapsed gt timeout     throw new RuntimeException  tiomeout      If the code itself cannot check for timeout  you can execute the code on another thread  and wait for completion  or timeout       Callable lt ResultType gt  run   new Callable lt ResultType gt                   Override         public ResultType call   throws Exception                          your code to be timed                       RunnableFuture future   new FutureTask run       ExecutorService service   Executors newSingleThreadExecutor        service execute future       ResultType result   null      try               result   future get 1  TimeUnit SECONDS         wait 1 second           catch  TimeoutException ex                   timed out  Try to stop the code if possible          future cancel true             service shutdown

[java] Java: set timeout on a certain block of code?

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