Path: csiph.com!v102.xanadu-bbs.net!xanadu-bbs.net!feeder.erje.net!eu.feeder.erje.net!ecngs!feeder2.ecngs.de!217.188.199.168.MISMATCH!takemy.news.telefonica.de!telefonica.de!feed.news.schlund.de!schlund.de!news.online.de!not-for-mail From: Philipp Kraus Newsgroups: comp.lang.java.programmer Subject: Re: thread pool Date: Tue, 22 Jul 2014 23:01:22 +0200 Organization: 1&1 Internet AG Lines: 386 Message-ID: References: NNTP-Posting-Host: p5b0c5f17.dip0.t-ipconnect.de Mime-Version: 1.0 Content-Type: multipart/alternative; boundary=--------------14507420321856879769 X-Trace: online.de 1406062882 6310 91.12.95.23 (22 Jul 2014 21:01:22 GMT) X-Complaints-To: abuse@einsundeins.com NNTP-Posting-Date: Tue, 22 Jul 2014 21:01:22 +0000 (UTC) User-Agent: Unison/2.1.10 Xref: csiph.com comp.lang.java.programmer:29208 This is a multi-part message in MIME format. ----------------14507420321856879769 Content-Type: text/plain; charset=iso-8859-1; format=flowed Content-Transfer-Encoding: 8bit On 2014-07-22 20:29:51 +0000, Eric Sosman said: > On 7/22/2014 3:38 PM, Philipp Kraus wrote: >> On 2014-07-22 13:11:14 +0000, Eric Sosman said: >> >>> On 7/22/2014 9:00 AM, Philipp Kraus wrote: >>>> Hello, >>>> >>>> I would like to create a thread pool with threads, which are should >>>> stopped by the user. >>>> So I create my pool with >>>> >>>> m_pool = Executors.newCachedThreadPool(); >>>> for (int i = 0; i < m_barrier.getParties(); i++) >>>> m_pool.submit(new Worker(m_barrier)); >>>> >>>> my Worker implements Runnable with the run-method >>>> >>>> while (!Thread.currentThread().isInterrupted()) { >>>> // do something >>>> } >>>> >>>> Within the while-loop I run my barrier and I catch the >>>> InterruptedException >>>> >>>> I would like to create a thread pool with a number of threads, which >>>> runs until the user >>>> sends a stop signal. At the moment I run m_pool.shutdown() and/or >>>> shutdownNow(), but >>>> which way is the correct Java structure. My target is, that a method >>>> creates all threads >>>> of the pool, each thread runs unlimited time until the user sends a stop >>>> signal. >>> >>> If "each thread runs unlimited time," why use a thread pool? The >>> purpose of this kind of pool is to run many short-lived (usually) tasks >>> on a set of threads, with each thread handling many tasks in succession. >>> You don't need that (it seems), so wouldn't it be simpler to launch >>> as many threads as you want and just let them run? When it's time to >>> stop you can interrupt them all (telling them to quit) and join them >>> all (so you'll know when all the quitting's finished). >>> >>> If that doesn't seem to meet your need, please describe what you're >>> trying to do in more detail. >> >> This works very fast :-) but I have got a problem with the thread >> interrupt. >> I create a thread pool with: >> >> m_threadcounter = new CountDownLatch(m_barrier.getParties()); >> for (int i = 0; i < m_barrier.getParties(); i++) >> new CWorker(m_runners, m_threadcounter, m_barrier, i == 0, m_world, >> m_currentstep).start(); >> >> and stop the pool with: >> >> try { >> >> m_runners.interrupt(); >> m_threadcounter.await(); >> >> } catch (InterruptedException l_exception) { >> m_Logger.error(l_exception.getMessage()); >> } >> >> m_runners is a ThreadGroup; >> >> The thread run shows: >> >> while (!Thread.currentThread().isInterrupted()) { >> >> // do something >> >> try { >> Thread.sleep(CConfiguration.getInstance().get().ThreadSleepTime); >> } catch (InterruptedException l_exception) { >> Thread.currentThread().interrupt(); >> } >> >> } >> >> m_counter.countDown(); >> >> This works fine on the first run. After I run the stop part once and run >> the creation part again >> all new threads a stopped, because the interrupt flag is set, so my new >> thread dows not run the while >> loop within the run. >> >> So I would like to create a a thread group, run it, stop it and create a >> group again. I cannot set the thread to >> sleep, because the data which is used by the threads must be >> reinitialize if the group is created > > The normal pattern is for the interrupted Thread to terminate, > either by returning from its run() method (or its Runnable's run() > method) or by throwing an uncaught Exception (InterruptedException, > for example). The control thread can call join() on the terminating > workers to learn when they've all stopped. Then to start anew you'd > create a new batch of worker Threads, and all of them would go through > whatever initialization you like. > > Here's one way to arrange things (there are many others), just > typed in without testing: > > class Worker implements Runnable { > ... > public void run() { > try { > for(;;) { > // do something > Thread.sleep(interval); > } > } catch (InterruptedException ex) { > // Stop running, but otherwise ignore > } > } > ... > } > > class Master { > ... > private List threads = new ArrayList<>(); > ... > void startThreads(int howMany) { > while (--howMany >= 0) { > Thread t = new Thread(new Worker()); > t.start(); > threads.add(t); > } > } > ... > void stopThreads() { > // Tell all the workers to stop: > for (Thread t : threads) { > t.interrupt(); > } > // Wait until they have all done so: > for (Thread t : threads) { > try { > t.join(); > } catch (InterruptedException ex) { > // The *Master* has been interrupted -- this may > // be reason to panic, log a failure message, > // and shut down the whole application > } > } > threads.clear(); // All the old Threads are gone. > } > ... > } > > I've never used ThreadGroup, so I can't offer advice on it. (Java > may be using ThreadGroup behind the scenes when I operate on Threads and > Executors and so on, but I've never had a reason to use ThreadGroup > directly.) My solution seems to be similar, but if I run your startThreads again the t.start(); throws the InterruptedException directly, so I do main() { Master x = new Master(); x.startThreads(5); x.stopThreads(); x.startThreads(5); <= this does not work because the exception is thrown } Phil ----------------14507420321856879769 Content-Type: text/html; charset=iso-8859-1 Content-Transfer-Encoding: 8bit

On 2014-07-22 20:29:51 +0000, Eric Sosman said:


On 7/22/2014 3:38 PM, Philipp Kraus wrote:

On 2014-07-22 13:11:14 +0000, Eric Sosman said:


On 7/22/2014 9:00 AM, Philipp Kraus wrote:

Hello,


I would like to create a thread pool with threads, which are should

stopped by the user.

So I create my pool with


m_pool = Executors.newCachedThreadPool();

for (int i = 0; i < m_barrier.getParties(); i++)

m_pool.submit(new Worker(m_barrier));


my Worker implements Runnable with the run-method


while (!Thread.currentThread().isInterrupted()) {

// do something

}


Within the while-loop I run my barrier and I catch the

InterruptedException


I would like to create a thread pool with a number of threads, which

runs until the user

sends a stop signal. At the moment I run m_pool.shutdown() and/or

shutdownNow(), but

which way is the correct Java structure. My target is, that a method

creates all threads

of the pool, each thread runs unlimited time until the user sends a stop

signal.


If "each thread runs unlimited time," why use a thread pool?  The

purpose of this kind of pool is to run many short-lived (usually) tasks

on a set of threads, with each thread handling many tasks in succession.

You don't need that (it seems), so wouldn't it be simpler to launch

as many threads as you want and just let them run?  When it's time to

stop you can interrupt them all (telling them to quit) and join them

all (so you'll know when all the quitting's finished).


If that doesn't seem to meet your need, please describe what you're

trying to do in more detail.


This works very fast :-) but I have got a problem with the thread

interrupt.

I create a thread pool with:


m_threadcounter = new CountDownLatch(m_barrier.getParties());

for (int i = 0; i < m_barrier.getParties(); i++)

new CWorker(m_runners, m_threadcounter, m_barrier, i == 0, m_world,

m_currentstep).start();


and stop the pool with:


try {


m_runners.interrupt();

m_threadcounter.await();


} catch (InterruptedException l_exception) {

m_Logger.error(l_exception.getMessage());

}


m_runners is a ThreadGroup;


The thread run shows:


while (!Thread.currentThread().isInterrupted()) {


// do something


try {

Thread.sleep(CConfiguration.getInstance().get().ThreadSleepTime);

} catch (InterruptedException l_exception) {

Thread.currentThread().interrupt();

}


}


m_counter.countDown();


This works fine on the first run. After I run the stop part once and run

the creation part again

all new threads a stopped, because the interrupt flag is set, so my new

thread dows not run the while

loop within the run.


So I would like to create a a thread group, run it, stop it and create a

group again. I cannot set the thread to

sleep, because the data which is used by the threads must be

reinitialize if the group is created


     The normal pattern is for the interrupted Thread to terminate,

either by returning from its run() method (or its Runnable's run()

method) or by throwing an uncaught Exception (InterruptedException,

for example).  The control thread can call join() on the terminating

workers to learn when they've all stopped.  Then to start anew you'd

create a new batch of worker Threads, and all of them would go through

whatever initialization you like.


     Here's one way to arrange things (there are many others), just

typed in without testing:


class Worker implements Runnable {

    ...

    public void run() {

        try {

            for(;;) {

                // do something

                Thread.sleep(interval);

            }

        } catch (InterruptedException ex) {

            // Stop running, but otherwise ignore

        }

    }

    ...

}


class Master {

    ...

    private List<Thread> threads = new ArrayList<>();

    ...

    void startThreads(int howMany) {

        while (--howMany >= 0) {

            Thread t = new Thread(new Worker());

            t.start();

            threads.add(t);

        }

    }

    ...

    void stopThreads() {

        // Tell all the workers to stop:

        for (Thread t : threads) {

            t.interrupt();

        }

        // Wait until they have all done so:

        for (Thread t : threads) {

            try {

                t.join();

            } catch (InterruptedException ex) {

                // The *Master* has been interrupted -- this may

                // be reason to panic, log a failure message,

                // and shut down the whole application

            }

        }

        threads.clear();  // All the old Threads are gone.

    }

    ...

}


     I've never used ThreadGroup, so I can't offer advice on it.  (Java

may be using ThreadGroup behind the scenes when I operate on Threads and

Executors and so on, but I've never had a reason to use ThreadGroup

directly.)


My solution seems to be similar, but if I run your startThreads again the  t.start();

throws the InterruptedException directly, so I do


main()

{

Master x = new Master();


x.startThreads(5);

x.stopThreads();

x.startThreads(5); <= this does not work because the exception is thrown

}


Phil

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