java - Better way to handle Uncaught Exceptions in ForkJoinPool Tasks/action -

java - Better way to handle Uncaught Exceptions in ForkJoinPool Tasks/action -

what improve way handle exceptions(uncaught) while using forkjoinpool submit tasks (recursiveaction or recursivetask)?

forkjoinpool accepts thread.uncaughtexceptionhandler handle exceptions when workerthread terminates abruptly(which anyways not under our control) handler not used when forkjointask throws exception. using standard submit/invokeall way in implementation.

here scenario:

i have thread running in infinite loop reading info 3rd party system. in thread submit tasks forkjoinpool

new thread() { public void run() { while (true) { forkjointask<void> uselessreturn = forkjoinpool.submit(recursiveactiontask); } } }

i using recursiveaction , in few scenarios recursivetask. these tasks submitted fjpool using submit() method. want have generic exception handler similar uncaughtexceptionhandler if task throws unchecked/uncaught exception can process exception , re-submit task if required. handling exception ensures queued tasks not cancelled if one/some of tasks throw exception.

invokeall() method returns set of forkjointasks these tasks in recursive block (each task invokes compute() method , may split farther [hypothetical scenario] )

class recursiveactiontask extends recursiveaction { public void compute() { if <task.size() <= acceptable_size) { processtask() // might throw checked/unchecked exception } else { recursiveactiontask[] splittasks = splittasks(tasks) recursiveactiontasks returnedtasks = invokeall(splittasks); // below code never executes invokeall submits tasks pool // , flow never comes code below. // looking handling (recusiveactiontask task : returnedtasks) { if (task.isdone()) { task.getexception() // handle exception } } } } }

i noticed when 3-4 tasks fail whole queue submission unit discarded. have set try/catch around processtask don't like. looking more generic.

i want know list of tasks failed can re-submit them when tasks throw exceptions threads evicted pool (although analysis found doesn't [but not sure] )? calling get() method on futuretask more set flow sequential waits until task completes. i want know status of task if fails. don't care when completes (obviously doesn't want wait hr later)

any ideas how handle exceptions in above scenario?

this show solved in akka:

/** * internal akka usage */ final class mailboxexecutiontask(mailbox: mailbox) extends forkjointask[unit] { final override def setrawresult(u: unit): unit = () final override def getrawresult(): unit = () final override def exec(): boolean = seek { mailbox.run; true } grab { case ⇒ val t = thread.currentthread t.getuncaughtexceptionhandler match { case null ⇒ case ⇒ some.uncaughtexception(t, anything) } throw } }

java multithreading java-7 java.util.concurrent fork-join