Dépôt officiel du code source de l'ERP OpenConcerto

/*

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.

 *

 * Copyright 2011 OpenConcerto, by ILM Informatique. All rights reserved.

 *

 * The contents of this file are subject to the terms of the GNU General Public License Version 3

 * only ("GPL"). You may not use this file except in compliance with the License. You can obtain a

 * copy of the License at http://www.gnu.org/licenses/gpl-3.0.html See the License for the specific

 * language governing permissions and limitations under the License.

 *

 * When distributing the software, include this License Header Notice in each file.

 */

 package org.openconcerto.utils;

import org.openconcerto.utils.cc.IClosure;

import org.openconcerto.utils.cc.IPredicate;

import java.beans.PropertyChangeListener;

import java.beans.PropertyChangeSupport;

import java.util.Collection;

import java.util.Deque;

import java.util.concurrent.Callable;

import java.util.concurrent.CancellationException;

import java.util.concurrent.ExecutionException;

import java.util.concurrent.Future;

import java.util.concurrent.FutureTask;

import java.util.concurrent.ScheduledFuture;

import java.util.concurrent.ScheduledThreadPoolExecutor;

import java.util.concurrent.TimeUnit;

import java.util.concurrent.atomic.AtomicBoolean;

import java.util.concurrent.atomic.AtomicReference;

import java.util.logging.Level;

import net.jcip.annotations.GuardedBy;

/**

 * A queue that can be put to sleep. Submitted runnables are converted to FutureTask, that can later

 * be cancelled.

 *

 * @author Sylvain

 */

public class SleepingQueue {

    public static enum RunningState {

        NEW, RUNNING, WILL_DIE, DYING, DEAD

    }

    /**

     * A task that can kill a queue.

     *

     * @author Sylvain

     *

     * @param <V> The result type returned by this FutureTask's <tt>get</tt> method

     */

    public static final class LethalFutureTask<V> extends FutureTask<V> {

        private final SleepingQueue q;

        public LethalFutureTask(final SleepingQueue q, final Callable<V> c) {

            super(c);

            this.q = q;

        }

        public final SleepingQueue getQueue() {

            return this.q;

        }

        @Override

        public String toString() {

            // don't includeCurrentTask as it could be us

            return this.getClass().getSimpleName() + " for " + this.getQueue().toString(false);

        }

    }

    private static final ScheduledThreadPoolExecutor exec;

    static {

        // daemon thread to allow the VM to exit

        exec = new ScheduledThreadPoolExecutor(2, new ThreadFactory("DieMonitor", true).setPriority(Thread.MIN_PRIORITY));

        // allow threads to die

        exec.setKeepAliveTime(30, TimeUnit.SECONDS);

        exec.allowCoreThreadTimeOut(true);

        exec.setContinueExistingPeriodicTasksAfterShutdownPolicy(false);

        exec.setExecuteExistingDelayedTasksAfterShutdownPolicy(false);

        assert exec.getPoolSize() == 0 : "Wasting resources";

    }

    public static final ScheduledFuture<?> watchDying(final LethalFutureTask<?> lethalFuture) {

        return watchDying(lethalFuture, 1, 1, TimeUnit.MINUTES);

    }

    /**

     * Watch the passed future until it's done. When

     * {@link SleepingQueue#die(boolean, Runnable, Callable) killing} a queue, the currently running

     * task must first complete then the actual killing (represented by a {@link LethalFutureTask})

     * begins. This involves running methods and passed runnables which can all hang or throw an

     * exception. Therefore this method will periodically report on the status of the killing, and

     * report any exception that was thrown.

     *

     * @param lethalFuture the killing to watch.

     * @param initialDelay the time to delay first execution.

     * @param delay the delay between the termination of one execution and the commencement of the

     *        next.

     * @param unit the time unit of the initialDelay and delay parameters.

     * @return a future representing the watching.

     */

    public static final ScheduledFuture<?> watchDying(final LethalFutureTask<?> lethalFuture, final int initialDelay, final int delay, final TimeUnit unit) {

        return watchDying(lethalFuture, initialDelay, delay, unit, null);

    }

    static final ScheduledFuture<?> watchDying(final LethalFutureTask<?> lethalFuture, final int initialDelay, final int delay, final TimeUnit unit,

            final IClosure<? super ExecutionException> exnHandler) {

        // don't use fixed rate as it might burden our threads and if we just checked the status

        // while being late, there's no need to check sooner the next time.

        final AtomicReference<Future<?>> f = new AtomicReference<Future<?>>();

        final ScheduledFuture<?> res = exec.scheduleWithFixedDelay(new Runnable() {

            // lethalFuture won't kill the queue, i.e. willDie threw an exception and forceDie was

            // false.

            private void wontKill(final RunningState runningState, final boolean isDone) {

                Log.get().fine("Our watched future won't kill the queue, current state : " + runningState + " " + lethalFuture);

                if (isDone)

                    cancel();

            }

            private void cancel() {

                assert lethalFuture.isDone();

                try {

                    lethalFuture.get();

                } catch (InterruptedException e) {

                    // either we were cancelled or the executor is shutting down (i.e. the VM is

                    // terminating)

                    Log.get().log(Level.FINER, "Interrupted while waiting on a finished future " + lethalFuture, e);

                } catch (ExecutionException e) {

                    if (exnHandler == null)

                        Log.get().log(Level.WARNING, "Threw an exception : " + lethalFuture, e);

                    else

                        exnHandler.executeChecked(e);

                }

                f.get().cancel(true);

            }

            @Override

            public void run() {

                final boolean isDone;

                final RunningState runningState;

                final FutureTask<?> beingRun;

                final SleepingQueue q = lethalFuture.getQueue();

                synchronized (q) {

                    runningState = q.getRunningState();

                    beingRun = q.getBeingRun();

                    isDone = lethalFuture.isDone();

                }

                final Level l = Level.INFO;

                if (runningState == RunningState.RUNNING) {

                    // willDie threw an exception but lethalFuture might not be completely done

                    // in that case, wait for the next execution

                    wontKill(runningState, isDone);

                } else if (runningState == RunningState.WILL_DIE) {

                    if (isDone) {

                        wontKill(runningState, isDone);

                    } else if (beingRun == lethalFuture) {

                        // in willDie() method or Runnable

                        Log.get().log(l, "Pre-death has not yet finished " + lethalFuture);

                    } else {

                        Log.get().log(l, "Death has not yet begun for " + lethalFuture + "\ncurrently running : " + beingRun);

                    }

                } else if (runningState == RunningState.DYING) {

                    assert beingRun == null || beingRun instanceof LethalFutureTask;

                    if (beingRun == null) {

                        // should be dead real soon

                        // just wait for the next execution

                        assert isDone;

                        Log.get().log(l, "Death was carried out but the thread is not yet terminated. Watching " + lethalFuture);

                    } else if (beingRun == lethalFuture) {

                        // in dying() method or Callable

                        Log.get().log(l, "Post-death has not yet finished " + lethalFuture);

                    } else {

                        assert isDone;

                        wontKill(runningState, isDone);

                    }

                } else if (runningState == RunningState.DEAD) {

                    // OK

                    Log.get().log(l, "Death was carried out and the thread is terminated but not necessarily by " + lethalFuture);

                    cancel();

                } else {

                    Log.get().warning("Illegal state " + runningState + " for " + lethalFuture);

                }

            }

        }, initialDelay, delay, unit);

        f.set(res);

        return res;

    }

    private final String name;

    @GuardedBy("this")

    private RunningState state;

    private final PropertyChangeSupport support;

    @GuardedBy("this")

    private FutureTask<?> beingRun;

    private final SingleThreadedExecutor tasksQueue;

    @GuardedBy("this")

    private boolean canceling;

    @GuardedBy("this")

    private IPredicate<FutureTask<?>> cancelPredicate;

    public SleepingQueue() {

        this(SleepingQueue.class.getName() + System.currentTimeMillis());

    }

    public SleepingQueue(String name) {

        super();

        this.name = name;

        this.state = RunningState.NEW;

        this.canceling = false;

        this.cancelPredicate = null;

        this.support = new PropertyChangeSupport(this);

        this.setBeingRun(null);

        this.tasksQueue = new SingleThreadedExecutor();

    }

    public final void start() {

        synchronized (this) {

            this.tasksQueue.start();

            this.setState(RunningState.RUNNING);

            started();

        }

    }

    /**

     * Start this queue only if not already started.

     *

     * @return <code>true</code> if the queue was started.

     */

    public final boolean startIfNew() {

        // don't use getRunningState() which calls isAlive()

        synchronized (this) {

            final boolean starting = this.state == RunningState.NEW;

            if (starting)

                this.start();

            assert this.state.compareTo(RunningState.NEW) > 0;

            return starting;

        }

    }

    protected void started() {

    }

    protected synchronized final void setState(final RunningState s) {

        this.state = s;

    }

    public synchronized final RunningState getRunningState() {

        // an Error could have stopped our thread so can't rely on this.state

        if (this.state == RunningState.NEW || this.tasksQueue.isAlive())

            return this.state;

        else

            return RunningState.DEAD;

    }

    public final boolean currentlyInQueue() {

        return Thread.currentThread() == this.tasksQueue;

    }

    /**

     * Customize the thread used to execute the passed runnables. This implementation sets the

     * priority to the minimum.

     *

     * @param thr the thread used by this queue.

     */

    protected void customizeThread(Thread thr) {

        thr.setPriority(Thread.MIN_PRIORITY);

    }

    protected final <T> FutureTask<T> newTaskFor(final Runnable task) {

        return this.newTaskFor(task, null);

    }

    protected <T> FutureTask<T> newTaskFor(final Runnable task, T value) {

        return new IFutureTask<T>(task, value, " for {" + this.name + "}");

    }

    public final FutureTask<?> put(Runnable workRunnable) {

        // otherwise if passing a FutureTask, it will itself be wrapped in another FutureTask. The

        // outer FutureTask will call the inner one's run(), which just record any exception. So the

        // outer one's get() won't throw it and the exception will effectively be swallowed.

        final FutureTask<?> t;

        if (workRunnable instanceof FutureTask) {

            t = ((FutureTask<?>) workRunnable);

        } else {

            t = this.newTaskFor(workRunnable);

        }

        return this.execute(t);

    }

    public final <F extends FutureTask<?>> F execute(F t) {

        if (this.shallAdd(t)) {

            this.add(t);

            return t;

        } else

            return null;

    }

    private void add(FutureTask<?> t) {

        // no need to synchronize, if die() is called after our test, t won't be executed anyway

        if (this.dieCalled())

            throw new IllegalStateException("Already dead, cannot exec " + t);

        this.tasksQueue.put(t);

    }

    private final boolean shallAdd(FutureTask<?> runnable) {

        if (runnable == null)

            throw new NullPointerException("null runnable");

        try {

            this.willPut(runnable);

            return true;

        } catch (InterruptedException e) {

            // si on interrompt, ne pas ajouter

            return false;

        }

    }

    /**

     * Give subclass the ability to reject runnables.

     *

     * @param r the runnable that is being added.

     * @throws InterruptedException if r should not be added to this queue.

     */

    protected void willPut(FutureTask<?> r) throws InterruptedException {

    }

    /**

     * An exception was thrown by a task. This implementation merely

     * {@link Exception#printStackTrace()}.

     *

     * @param exn the exception thrown.

     */

    protected void exceptionThrown(final ExecutionException exn) {

        exn.printStackTrace();

    }

    /**

     * Cancel all queued tasks and the current task.

     */

    protected final void cancel() {

        this.cancel(null);

    }

    /**

     * Cancel only tasks for which pred is <code>true</code>.

     *

     * @param pred a predicate to know which tasks to cancel.

     */

    protected final void cancel(final IPredicate<FutureTask<?>> pred) {

        this.tasksDo(new IClosure<Collection<FutureTask<?>>>() {

            @Override

            public void executeChecked(Collection<FutureTask<?>> tasks) {

                cancel(pred, tasks);

            }

        });

    }

    private final void cancel(IPredicate<FutureTask<?>> pred, Collection<FutureTask<?>> tasks) {

        try {

            synchronized (this) {

                this.canceling = true;

                this.cancelPredicate = pred;

                this.cancelCheck(this.getBeingRun());

            }

            for (final FutureTask<?> t : tasks) {

                this.cancelCheck(t);

            }

        } finally {

            synchronized (this) {

                this.canceling = false;

                // allow the predicate to be gc'd

                this.cancelPredicate = null;

            }

        }

    }

    public final void tasksDo(IClosure<? super Deque<FutureTask<?>>> c) {

        this.tasksQueue.itemsDo(c);

    }

    private void cancelCheck(FutureTask<?> t) {

        if (t != null)

            synchronized (this) {

                if (this.canceling && (this.cancelPredicate == null || this.cancelPredicate.evaluateChecked(t)))

                    t.cancel(true);

            }

    }

    private void setBeingRun(final FutureTask<?> beingRun) {

        final Future<?> old;

        synchronized (this) {

            old = this.beingRun;

            this.beingRun = beingRun;

        }

        this.support.firePropertyChange("beingRun", old, beingRun);

    }

    public final synchronized FutureTask<?> getBeingRun() {

        return this.beingRun;

    }

    public boolean isSleeping() {

        return this.tasksQueue.isSleeping();

    }

    public boolean setSleeping(boolean sleeping) {

        final boolean res = this.tasksQueue.setSleeping(sleeping);

        if (res) {

            this.support.firePropertyChange("sleeping", null, sleeping);

        }

        return res;

    }

    /**

     * Stops this queue. Once this method returns, it is guaranteed that no other task will be taken

     * from the queue to be started, and that this queue will die. But the already executing task

     * will complete unless it checks for interrupt.

     *

     * @return the future killing.

     */

    public final LethalFutureTask<?> die() {

        return this.die(true, null, null);

    }

    /**

     * Stops this queue. All tasks in the queue, including the {@link #getBeingRun() currently

     * running}, will be {@link Future#cancel(boolean) cancelled}. The currently running task will

     * thus complete unless it checks for interrupt. Once the returned future completes successfully

     * then no task is executing ( {@link #isDead()} will happen sometimes later, the time for the

     * thread to terminate). If the returned future throws an exception because of the passed

     * runnables or of {@link #willDie()} or {@link #dying()}, one can check with

     * {@link #dieCalled()} to see if the queue is dying.

     * <p>

     * This method tries to limit the cases where the returned Future will not get executed : it

     * checks that this was {@link #start() started} and is not already {@link RunningState#DYING}

     * or {@link RunningState#DEAD}. It also doesn't allow {@link RunningState#WILL_DIE} as it could

     * cancel the previously passed runnables or never run the passed runnables. But even with these

     * restrictions a number of things can prevent the result from getting executed : the

     * {@link #getBeingRun() currently running} task hangs indefinitely, it throws an {@link Error}

     * ; the passed runnables hang indefinitely.

     * </p>

     *

     * @param force <code>true</code> if this is guaranteed to die (even if <code>willDie</code> or

     *        {@link #willDie()} throw an exception).

     * @param willDie the last actions to take before killing this queue.

     * @param dying the last actions to take before this queue is dead.

     * @return the future killing, which will return <code>dying</code> result.

     * @throws IllegalStateException if the state isn't {@link RunningState#RUNNING}.

     * @see #dieCalled()

     */

    public final <V> LethalFutureTask<V> die(final boolean force, final Runnable willDie, final Callable<V> dying) throws IllegalStateException {

        synchronized (this) {

            final RunningState state = this.getRunningState();

            if (state == RunningState.NEW)

                throw new IllegalStateException("Not started");

            if (state.compareTo(RunningState.RUNNING) > 0)

                throw new IllegalStateException("die() already called or thread was killed by an Error : " + state);

            assert state == RunningState.RUNNING;

            this.setState(RunningState.WILL_DIE);

        }

        // reset sleeping to original value if die not effective

        final AtomicBoolean resetSleeping = new AtomicBoolean(false);

        final LethalFutureTask<V> res = new LethalFutureTask<V>(this, new Callable<V>() {

            @Override

            public V call() throws Exception {

                Exception willDieExn = null;

                try {

                    willDie();

                    if (willDie != null) {

                        willDie.run();

                        // handle Future like runnable, i.e. check right away for exception

                        if (willDie instanceof Future) {

                            final Future<?> f = (Future<?>) willDie;

                            assert f.isDone() : "Ran but not done: " + f;

                            try {

                                f.get();

                            } catch (ExecutionException e) {

                                throw (Exception) e.getCause();

                            }

                        }

                    }

                } catch (Exception e) {

                    if (!force) {

                        setState(RunningState.RUNNING);

                        throw e;

                    } else {

                        willDieExn = e;

                    }

                }

                try {

                    // don't interrupt ourselves

                    SleepingQueue.this.tasksQueue.die(false);

                    assert SleepingQueue.this.tasksQueue.isDying();

                    setState(RunningState.DYING);

                    // since there's already been an exception, throw it as soon as possible

                    // also dying() might itself throw an exception for the same reason or we now

                    // have 2 exceptions to throw

                    if (willDieExn != null)

                        throw willDieExn;

                    dying();

                    final V res;

                    if (dying != null)

                        res = dying.call();

                    else

                        res = null;

                    return res;

                } finally {

                    // if die is effective, this won't have any consequences

                    if (resetSleeping.get())

                        SleepingQueue.this.tasksQueue.setSleeping(true);

                }

            }

        });

        // die as soon as possible not after all currently queued tasks

        this.tasksQueue.itemsDo(new IClosure<Deque<FutureTask<?>>>() {

            @Override

            public void executeChecked(Deque<FutureTask<?>> input) {

                // since we cancel the current task, we might as well remove all of them since they

                // might depend on the cancelled one

                // cancel removed tasks so that callers of get() don't wait forever

                for (final FutureTask<?> ft : input) {

                    // by definition tasks in the queue aren't executing, so interrupt parameter is

                    // useless. On the other hand cancel() might return false if already cancelled.

                    ft.cancel(false);

                }

                input.clear();

                input.addFirst(res);

                // die as soon as possible, even if there's a long task already running

                final FutureTask<?> beingRun = getBeingRun();

                // since we hold the lock on items

                assert beingRun != res : "beingRun: " + beingRun + " ; res: " + res;

                if (beingRun != null)

                    beingRun.cancel(true);

            }

        });

        // force execution of our task

        resetSleeping.set(this.setSleeping(false));

        return res;

    }

    protected void willDie() {

        // nothing by default

    }

    protected void dying() throws Exception {

        // nothing by default

    }

    /**

     * Whether this will die. If this method returns <code>true</code>, it is guaranteed that no

     * other task will be taken from the queue to be started. Note: this method doesn't return

     * <code>true</code> right after {@link #die()} as the method is asynchronous and if

     * {@link #willDie()} fails it may not die at all ; as explained in its comment you may use its

     * returned future to wait for the killing.

     *

     * @return <code>true</code> if this queue will not execute any more tasks (but it may hang

     *         indefinitely if the dying runnable blocks).

     * @see #isDead()

     */

    public final boolean dieCalled() {

        return this.tasksQueue.dieCalled();

    }

    /**

     * Whether this queue is dead, i.e. if die() has been called and all tasks have completed.

     *

     * @return <code>true</code> if this queue will not execute any more tasks and isn't executing

     *         any.

     * @see #die()

     */

    public final boolean isDead() {

        return this.tasksQueue.isDead();

    }

    /**

     * Allow to wait for the thread to end. Once this method returns {@link #getRunningState()} will

     * always return {@link RunningState#DEAD}. Useful since the future from

     * {@link #die(boolean, Runnable, Callable)} returns when all tasks are finished but the

     * {@link #getRunningState()} is still {@link RunningState#DYING} since the Thread takes a

     * little time to die.

     *

     * @throws InterruptedException if interrupted while waiting.

     * @see Thread#join()

     */

    public final void join() throws InterruptedException {

        this.tasksQueue.join();

    }

    public final void join(long millis, int nanos) throws InterruptedException {

        this.tasksQueue.join(millis, nanos);

    }

    public void addPropertyChangeListener(PropertyChangeListener l) {

        this.support.addPropertyChangeListener(l);

    }

    public void rmPropertyChangeListener(PropertyChangeListener l) {

        this.support.removePropertyChangeListener(l);

    }

    private final class SingleThreadedExecutor extends DropperQueue<FutureTask<?>> {

        private SingleThreadedExecutor() {

            super(SleepingQueue.this.name + System.currentTimeMillis());

            customizeThread(this);

        }

        @Override

        protected void process(FutureTask<?> task) {

            if (!task.isDone()) {

                /*

                 * From ThreadPoolExecutor : Track execution state to ensure that afterExecute is

                 * called only if task completed or threw exception. Otherwise, the caught runtime

                 * exception will have been thrown by afterExecute itself, in which case we don't

                 * want to call it again.

                 */

                boolean ran = false;

                beforeExecute(task);

                try {

                    task.run();

                    ran = true;

                    afterExecute(task, null);

                } catch (RuntimeException ex) {

                    if (!ran)

                        afterExecute(task, ex);

                    // don't throw ex, afterExecute() can do whatever needs to be done (like killing

                    // this queue)

                }

            }

        }

        protected void beforeExecute(final FutureTask<?> f) {

            cancelCheck(f);

            setBeingRun(f);

        }

        protected void afterExecute(final FutureTask<?> f, final Throwable t) {

            setBeingRun(null);

            try {

                f.get();

            } catch (CancellationException e) {

                // don't care

            } catch (InterruptedException e) {

                // f was interrupted : e.g. we're dying or f was cancelled

            } catch (ExecutionException e) {

                // f.run() raised an exception

                exceptionThrown(e);

            }

        }

    }

    @Override

    public String toString() {

        return this.toString(true);

    }

    public String toString(final boolean includeCurrentTask) {

        return super.toString() + " Queue: " + this.tasksQueue + (includeCurrentTask ? " run:" + this.getBeingRun() : "");

    }

}