Add GlobalEventExecutor

- Related issue: #1389
- Also extracted SingleThreadEventExecutor.ScheduledFutureTask into a top level class for a reuse

common/src/main/java/io/netty/util/concurrent/AbstractEventExecutor.java

@@ -34,6 +34,11 @@ public abstract class AbstractEventExecutor extends AbstractExecutorService impl
         return this;
     }
 
+    @Override
+    public boolean inEventLoop() {
+        return inEventLoop(Thread.currentThread());
+    }
+
     @Override
     public Iterator<EventExecutor> iterator() {
         return new EventExecutorIterator();

common/src/main/java/io/netty/util/concurrent/GlobalEventExecutor.java

@@ -0,0 +1,356 @@
+/*
+ * Copyright 2012 The Netty Project
+ *
+ * The Netty Project licenses this file to you under the Apache License,
+ * version 2.0 (the "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at:
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ */
+package io.netty.util.concurrent;
+
+import io.netty.util.internal.logging.InternalLogger;
+import io.netty.util.internal.logging.InternalLoggerFactory;
+
+import java.util.Iterator;
+import java.util.PriorityQueue;
+import java.util.Queue;
+import java.util.concurrent.BlockingQueue;
+import java.util.concurrent.Callable;
+import java.util.concurrent.Executors;
+import java.util.concurrent.LinkedBlockingQueue;
+import java.util.concurrent.RejectedExecutionException;
+import java.util.concurrent.ThreadFactory;
+import java.util.concurrent.TimeUnit;
+
+/**
+ * Single-thread singleton {@link EventExecutor}.  It starts the thread automatically and stops it when there is no
+ * task pending in the task queue for 1 second.  Please note it is not scalable to schedule large number of tasks to
+ * this executor; use a dedicated executor.
+ */
+public final class GlobalEventExecutor extends AbstractEventExecutor {
+
+    private static final InternalLogger logger = InternalLoggerFactory.getInstance(GlobalEventExecutor.class);
+
+    private static final int ST_NOT_STARTED = 1;
+    private static final int ST_STARTED = 2;
+
+    private static final long SCHEDULE_PURGE_INTERVAL = TimeUnit.SECONDS.toNanos(1);
+
+    public static final GlobalEventExecutor INSTANCE = new GlobalEventExecutor();
+
+    final Queue<Runnable> taskQueue = new LinkedBlockingQueue<Runnable>();
+    final Queue<ScheduledFutureTask<?>> delayedTaskQueue = new PriorityQueue<ScheduledFutureTask<?>>();
+    final ScheduledFutureTask<Void> purgeTask = new ScheduledFutureTask<Void>(
+            this, delayedTaskQueue, Executors.<Void>callable(new PurgeTask(), null),
+            ScheduledFutureTask.deadlineNanos(SCHEDULE_PURGE_INTERVAL), -SCHEDULE_PURGE_INTERVAL);
+
+    private final ThreadFactory threadFactory = new DefaultThreadFactory(getClass());
+    private final TaskRunner taskRunner = new TaskRunner();
+    private final Object stateLock = new Object();
+
+    volatile Thread thread;
+    private volatile int state = ST_NOT_STARTED;
+
+    private GlobalEventExecutor() {
+        delayedTaskQueue.add(purgeTask);
+    }
+
+    @Override
+    public EventExecutorGroup parent() {
+        return null;
+    }
+
+    /**
+     * Take the next {@link Runnable} from the task queue and so will block if no task is currently present.
+     *
+     * @return {@code null} if the executor thread has been interrupted or waken up.
+     */
+    Runnable takeTask() {
+        BlockingQueue<Runnable> taskQueue = (BlockingQueue<Runnable>) this.taskQueue;
+        for (;;) {
+            ScheduledFutureTask<?> delayedTask = delayedTaskQueue.peek();
+            if (delayedTask == null) {
+                Runnable task = null;
+                try {
+                    task = taskQueue.take();
+                } catch (InterruptedException e) {
+                    // Ignore
+                }
+                return task;
+            } else {
+                long delayNanos = delayedTask.delayNanos();
+                Runnable task;
+                if (delayNanos > 0) {
+                    try {
+                        task = taskQueue.poll(delayNanos, TimeUnit.NANOSECONDS);
+                    } catch (InterruptedException e) {
+                        return null;
+                    }
+                } else {
+                    task = taskQueue.poll();
+                }
+
+                if (task == null) {
+                    fetchFromDelayedQueue();
+                    task = taskQueue.poll();
+                }
+
+                if (task != null) {
+                    return task;
+                }
+            }
+        }
+    }
+
+    private void fetchFromDelayedQueue() {
+        long nanoTime = 0L;
+        for (;;) {
+            ScheduledFutureTask<?> delayedTask = delayedTaskQueue.peek();
+            if (delayedTask == null) {
+                break;
+            }
+
+            if (nanoTime == 0L) {
+                nanoTime = ScheduledFutureTask.nanoTime();
+            }
+
+            if (delayedTask.deadlineNanos() <= nanoTime) {
+                delayedTaskQueue.remove();
+                taskQueue.add(delayedTask);
+            } else {
+                break;
+            }
+        }
+    }
+
+    /**
+     * Return the number of tasks that are pending for processing.
+     *
+     * <strong>Be aware that this operation may be expensive as it depends on the internal implementation of the
+     * SingleThreadEventExecutor. So use it was care!</strong>
+     */
+    public int pendingTasks() {
+        return taskQueue.size();
+    }
+
+    /**
+     * Add a task to the task queue, or throws a {@link RejectedExecutionException} if this instance was shutdown
+     * before.
+     */
+    private void addTask(Runnable task) {
+        if (task == null) {
+            throw new NullPointerException("task");
+        }
+        taskQueue.add(task);
+    }
+
+    @Override
+    public boolean inEventLoop(Thread thread) {
+        return thread == this.thread;
+    }
+
+    @Override
+    public void shutdownGracefully(long quietPeriod, long timeout, TimeUnit unit) {
+        throw new UnsupportedOperationException();
+    }
+
+    @Override
+    @Deprecated
+    public void shutdown() {
+        throw new UnsupportedOperationException();
+    }
+
+    @Override
+    public boolean isShuttingDown() {
+        return false;
+    }
+
+    @Override
+    public boolean isShutdown() {
+        return false;
+    }
+
+    @Override
+    public boolean isTerminated() {
+        return false;
+    }
+
+    @Override
+    public boolean awaitTermination(long timeout, TimeUnit unit) {
+        return false;
+    }
+
+    @Override
+    public void execute(Runnable task) {
+        if (task == null) {
+            throw new NullPointerException("task");
+        }
+
+        boolean inEventLoop = inEventLoop();
+        if (inEventLoop) {
+            addTask(task);
+        } else {
+            startThread();
+            addTask(task);
+        }
+    }
+
+    // ScheduledExecutorService implementation
+
+    @Override
+    public ScheduledFuture<?> schedule(Runnable command, long delay, TimeUnit unit) {
+        if (command == null) {
+            throw new NullPointerException("command");
+        }
+        if (unit == null) {
+            throw new NullPointerException("unit");
+        }
+        if (delay < 0) {
+            throw new IllegalArgumentException(
+                    String.format("delay: %d (expected: >= 0)", delay));
+        }
+        return schedule(new ScheduledFutureTask<Void>(
+                this, delayedTaskQueue, command, null, ScheduledFutureTask.deadlineNanos(unit.toNanos(delay))));
+    }
+
+    @Override
+    public <V> ScheduledFuture<V> schedule(Callable<V> callable, long delay, TimeUnit unit) {
+        if (callable == null) {
+            throw new NullPointerException("callable");
+        }
+        if (unit == null) {
+            throw new NullPointerException("unit");
+        }
+        if (delay < 0) {
+            throw new IllegalArgumentException(
+                    String.format("delay: %d (expected: >= 0)", delay));
+        }
+        return schedule(new ScheduledFutureTask<V>(
+                this, delayedTaskQueue, callable, ScheduledFutureTask.deadlineNanos(unit.toNanos(delay))));
+    }
+
+    @Override
+    public ScheduledFuture<?> scheduleAtFixedRate(Runnable command, long initialDelay, long period, TimeUnit unit) {
+        if (command == null) {
+            throw new NullPointerException("command");
+        }
+        if (unit == null) {
+            throw new NullPointerException("unit");
+        }
+        if (initialDelay < 0) {
+            throw new IllegalArgumentException(
+                    String.format("initialDelay: %d (expected: >= 0)", initialDelay));
+        }
+        if (period <= 0) {
+            throw new IllegalArgumentException(
+                    String.format("period: %d (expected: > 0)", period));
+        }
+
+        return schedule(new ScheduledFutureTask<Void>(
+                this, delayedTaskQueue, Executors.<Void>callable(command, null),
+                ScheduledFutureTask.deadlineNanos(unit.toNanos(initialDelay)), unit.toNanos(period)));
+    }
+
+    @Override
+    public ScheduledFuture<?> scheduleWithFixedDelay(Runnable command, long initialDelay, long delay, TimeUnit unit) {
+        if (command == null) {
+            throw new NullPointerException("command");
+        }
+        if (unit == null) {
+            throw new NullPointerException("unit");
+        }
+        if (initialDelay < 0) {
+            throw new IllegalArgumentException(
+                    String.format("initialDelay: %d (expected: >= 0)", initialDelay));
+        }
+        if (delay <= 0) {
+            throw new IllegalArgumentException(
+                    String.format("delay: %d (expected: > 0)", delay));
+        }
+
+        return schedule(new ScheduledFutureTask<Void>(
+                this, delayedTaskQueue, Executors.<Void>callable(command, null),
+                ScheduledFutureTask.deadlineNanos(unit.toNanos(initialDelay)), -unit.toNanos(delay)));
+    }
+
+    private <V> ScheduledFuture<V> schedule(final ScheduledFutureTask<V> task) {
+        if (task == null) {
+            throw new NullPointerException("task");
+        }
+
+        if (inEventLoop()) {
+            delayedTaskQueue.add(task);
+        } else {
+            execute(new Runnable() {
+                @Override
+                public void run() {
+                    delayedTaskQueue.add(task);
+                }
+            });
+        }
+
+        return task;
+    }
+
+    private void startThread() {
+        synchronized (stateLock) {
+            if (state == ST_NOT_STARTED) {
+                state = ST_STARTED;
+
+                thread = threadFactory.newThread(taskRunner);
+
+                thread.start();
+            }
+        }
+    }
+
+    final class TaskRunner implements Runnable {
+        @Override
+        public void run() {
+            for (;;) {
+                Runnable task = takeTask();
+                if (task != null) {
+                    try {
+                        task.run();
+                    } catch (Throwable t) {
+                        logger.warn("Unexpected exception from the global event executor: ", t);
+                    }
+
+                    if (task != purgeTask) {
+                        continue;
+                    }
+                }
+
+                if (taskQueue.isEmpty() && delayedTaskQueue.size() == 1) {
+                    synchronized (stateLock) {
+                        // Terminate if there is no task in the queue (except the purge task).
+                        if (taskQueue.isEmpty() && delayedTaskQueue.size() == 1) {
+                            state = ST_NOT_STARTED;
+                            break;
+                        }
+                    }
+                }
+            }
+        }
+    }
+
+    private final class PurgeTask implements Runnable {
+        @Override
+        public void run() {
+            Iterator<ScheduledFutureTask<?>> i = delayedTaskQueue.iterator();
+            while (i.hasNext()) {
+                ScheduledFutureTask<?> task = i.next();
+                if (task.isCancelled()) {
+                    i.remove();
+                }
+            }
+        }
+    }
+}

common/src/main/java/io/netty/util/concurrent/ScheduledFutureTask.java

@@ -0,0 +1,148 @@
+/*
+ * Copyright 2013 The Netty Project
+ *
+ * The Netty Project licenses this file to you under the Apache License,
+ * version 2.0 (the "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at:
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ */
+
+package io.netty.util.concurrent;
+
+import java.util.Queue;
+import java.util.concurrent.Callable;
+import java.util.concurrent.Delayed;
+import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicLong;
+
+@SuppressWarnings("ComparableImplementedButEqualsNotOverridden")
+final class ScheduledFutureTask<V> extends PromiseTask<V> implements ScheduledFuture<V> {
+    private static final AtomicLong nextTaskId = new AtomicLong();
+    private static final long START_TIME = System.nanoTime();
+
+    static long nanoTime() {
+        return System.nanoTime() - START_TIME;
+    }
+
+    static long deadlineNanos(long delay) {
+        return nanoTime() + delay;
+    }
+
+    private final long id = nextTaskId.getAndIncrement();
+    private final Queue<ScheduledFutureTask<?>> delayedTaskQueue;
+    private long deadlineNanos;
+    /* 0 - no repeat, >0 - repeat at fixed rate, <0 - repeat with fixed delay */
+    private final long periodNanos;
+
+    ScheduledFutureTask(
+            EventExecutor executor, Queue<ScheduledFutureTask<?>> delayedTaskQueue,
+            Runnable runnable, V result, long nanoTime) {
+
+        this(executor, delayedTaskQueue, Executors.callable(runnable, result), nanoTime);
+    }
+
+    ScheduledFutureTask(
+            EventExecutor executor, Queue<ScheduledFutureTask<?>> delayedTaskQueue,
+            Callable<V> callable, long nanoTime, long period) {
+
+        super(executor, callable);
+        if (period == 0) {
+            throw new IllegalArgumentException("period: 0 (expected: != 0)");
+        }
+        this.delayedTaskQueue = delayedTaskQueue;
+        deadlineNanos = nanoTime;
+        periodNanos = period;
+    }
+
+    ScheduledFutureTask(
+            EventExecutor executor, Queue<ScheduledFutureTask<?>> delayedTaskQueue,
+            Callable<V> callable, long nanoTime) {
+
+        super(executor, callable);
+        this.delayedTaskQueue = delayedTaskQueue;
+        deadlineNanos = nanoTime;
+        periodNanos = 0;
+    }
+
+    @Override
+    protected EventExecutor executor() {
+        return super.executor();
+    }
+
+    public long deadlineNanos() {
+        return deadlineNanos;
+    }
+
+    public long delayNanos() {
+        return Math.max(0, deadlineNanos() - nanoTime());
+    }
+
+    public long delayNanos(long currentTimeNanos) {
+        return Math.max(0, deadlineNanos() - (currentTimeNanos - START_TIME));
+    }
+
+    @Override
+    public long getDelay(TimeUnit unit) {
+        return unit.convert(delayNanos(), TimeUnit.NANOSECONDS);
+    }
+
+    @Override
+    public int compareTo(Delayed o) {
+        if (this == o) {
+            return 0;
+        }
+
+        ScheduledFutureTask<?> that = (ScheduledFutureTask<?>) o;
+        long d = deadlineNanos() - that.deadlineNanos();
+        if (d < 0) {
+            return -1;
+        } else if (d > 0) {
+            return 1;
+        } else if (id < that.id) {
+            return -1;
+        } else if (id == that.id) {
+            throw new Error();
+        } else {
+            return 1;
+        }
+    }
+
+    @Override
+    public void run() {
+        assert executor().inEventLoop();
+        try {
+            if (periodNanos == 0) {
+                if (setUncancellableInternal()) {
+                    V result = task.call();
+                    setSuccessInternal(result);
+                }
+            } else {
+                // check if is done as it may was cancelled
+                if (!isCancelled()) {
+                    task.call();
+                    if (!executor().isShutdown()) {
+                        long p = periodNanos;
+                        if (p > 0) {
+                            deadlineNanos += p;
+                        } else {
+                            deadlineNanos = nanoTime() - p;
+                        }
+                        if (!isCancelled()) {
+                            delayedTaskQueue.add(this);
+                        }
+                    }
+                }
+            }
+        } catch (Throwable cause) {
+            setFailureInternal(cause);
+        }
+    }
+}

common/src/main/java/io/netty/util/concurrent/SingleThreadEventExecutor.java

@@ -27,14 +27,12 @@ import java.util.Queue;
 import java.util.Set;
 import java.util.concurrent.BlockingQueue;
 import java.util.concurrent.Callable;
-import java.util.concurrent.Delayed;
 import java.util.concurrent.Executors;
 import java.util.concurrent.LinkedBlockingQueue;
 import java.util.concurrent.RejectedExecutionException;
 import java.util.concurrent.Semaphore;
 import java.util.concurrent.ThreadFactory;
 import java.util.concurrent.TimeUnit;
-import java.util.concurrent.atomic.AtomicLong;
 
 /**
  * Abstract base class for {@link EventExecutor}'s that execute all its submitted tasks in a single thread.
@@ -243,7 +241,7 @@ public abstract class SingleThreadEventExecutor extends AbstractEventExecutor {
             }
 
             if (nanoTime == 0L) {
-                nanoTime = nanoTime();
+                nanoTime = ScheduledFutureTask.nanoTime();
             }
 
             if (delayedTask.deadlineNanos() <= nanoTime) {
@@ -326,7 +324,7 @@ public abstract class SingleThreadEventExecutor extends AbstractEventExecutor {
 
             task = pollTask();
             if (task == null) {
-                lastExecutionTime = nanoTime();
+                lastExecutionTime = ScheduledFutureTask.nanoTime();
                 return true;
             }
         }
@@ -343,7 +341,7 @@ public abstract class SingleThreadEventExecutor extends AbstractEventExecutor {
             return false;
         }
 
-        final long deadline = nanoTime() + timeoutNanos;
+        final long deadline = ScheduledFutureTask.nanoTime() + timeoutNanos;
         long runTasks = 0;
         long lastExecutionTime;
         for (;;) {
@@ -358,7 +356,7 @@ public abstract class SingleThreadEventExecutor extends AbstractEventExecutor {
             // Check timeout every 64 tasks because nanoTime() is relatively expensive.
             // XXX: Hard-coded value - will make it configurable if it is really a problem.
             if ((runTasks & 0x3F) == 0) {
-                lastExecutionTime = nanoTime();
+                lastExecutionTime = ScheduledFutureTask.nanoTime();
                 if (lastExecutionTime >= deadline) {
                     break;
                 }
@@ -366,7 +364,7 @@ public abstract class SingleThreadEventExecutor extends AbstractEventExecutor {
 
             task = pollTask();
             if (task == null) {
-                lastExecutionTime = nanoTime();
+                lastExecutionTime = ScheduledFutureTask.nanoTime();
                 break;
             }
         }
@@ -395,7 +393,7 @@ public abstract class SingleThreadEventExecutor extends AbstractEventExecutor {
      * checks.
      */
     protected void updateLastExecutionTime() {
-        lastExecutionTime = nanoTime();
+        lastExecutionTime = ScheduledFutureTask.nanoTime();
     }
 
     /**
@@ -416,11 +414,6 @@ public abstract class SingleThreadEventExecutor extends AbstractEventExecutor {
         }
     }
 
-    @Override
-    public boolean inEventLoop() {
-        return inEventLoop(Thread.currentThread());
-    }
-
     @Override
     public boolean inEventLoop(Thread thread) {
         return thread == this.thread;
@@ -476,7 +469,7 @@ public abstract class SingleThreadEventExecutor extends AbstractEventExecutor {
         }
 
         if (ran) {
-            lastExecutionTime = nanoTime();
+            lastExecutionTime = ScheduledFutureTask.nanoTime();
         }
 
         return ran;
@@ -602,7 +595,7 @@ public abstract class SingleThreadEventExecutor extends AbstractEventExecutor {
         cancelDelayedTasks();
 
         if (gracefulShutdownStartTime == 0) {
-            gracefulShutdownStartTime = nanoTime();
+            gracefulShutdownStartTime = ScheduledFutureTask.nanoTime();
         }
 
         if (runAllTasks() || runShutdownHooks()) {
@@ -616,7 +609,7 @@ public abstract class SingleThreadEventExecutor extends AbstractEventExecutor {
             return false;
         }
 
-        final long nanoTime = nanoTime();
+        final long nanoTime = ScheduledFutureTask.nanoTime();
 
         if (isShutdown() || nanoTime - gracefulShutdownStartTime > gracefulShutdownTimeout) {
             return true;
@@ -701,15 +694,6 @@ public abstract class SingleThreadEventExecutor extends AbstractEventExecutor {
     // ScheduledExecutorService implementation
 
     private static final long SCHEDULE_PURGE_INTERVAL = TimeUnit.SECONDS.toNanos(1);
-    private static final long START_TIME = System.nanoTime();
-    private static final AtomicLong nextTaskId = new AtomicLong();
-    private static long nanoTime() {
-        return System.nanoTime() - START_TIME;
-    }
-
-    private static long deadlineNanos(long delay) {
-        return nanoTime() + delay;
-    }
 
     @Override
     public ScheduledFuture<?> schedule(Runnable command, long delay, TimeUnit unit) {
@@ -723,7 +707,8 @@ public abstract class SingleThreadEventExecutor extends AbstractEventExecutor {
             throw new IllegalArgumentException(
                     String.format("delay: %d (expected: >= 0)", delay));
         }
-        return schedule(new ScheduledFutureTask<Void>(this, command, null, deadlineNanos(unit.toNanos(delay))));
+        return schedule(new ScheduledFutureTask<Void>(
+                this, delayedTaskQueue, command, null, ScheduledFutureTask.deadlineNanos(unit.toNanos(delay))));
     }
 
     @Override
@@ -738,7 +723,8 @@ public abstract class SingleThreadEventExecutor extends AbstractEventExecutor {
             throw new IllegalArgumentException(
                     String.format("delay: %d (expected: >= 0)", delay));
         }
-        return schedule(new ScheduledFutureTask<V>(this, callable, deadlineNanos(unit.toNanos(delay))));
+        return schedule(new ScheduledFutureTask<V>(
+                this, delayedTaskQueue, callable, ScheduledFutureTask.deadlineNanos(unit.toNanos(delay))));
     }
 
     @Override
@@ -759,8 +745,8 @@ public abstract class SingleThreadEventExecutor extends AbstractEventExecutor {
         }
 
         return schedule(new ScheduledFutureTask<Void>(
-                this, Executors.<Void>callable(command, null),
-                deadlineNanos(unit.toNanos(initialDelay)), unit.toNanos(period)));
+                this, delayedTaskQueue, Executors.<Void>callable(command, null),
+                ScheduledFutureTask.deadlineNanos(unit.toNanos(initialDelay)), unit.toNanos(period)));
     }
 
     @Override
@@ -781,8 +767,8 @@ public abstract class SingleThreadEventExecutor extends AbstractEventExecutor {
         }
 
         return schedule(new ScheduledFutureTask<Void>(
-                this, Executors.<Void>callable(command, null),
-                deadlineNanos(unit.toNanos(initialDelay)), -unit.toNanos(delay)));
+                this, delayedTaskQueue, Executors.<Void>callable(command, null),
+                ScheduledFutureTask.deadlineNanos(unit.toNanos(initialDelay)), -unit.toNanos(delay)));
     }
 
     private <V> ScheduledFuture<V> schedule(final ScheduledFutureTask<V> task) {
@@ -809,115 +795,13 @@ public abstract class SingleThreadEventExecutor extends AbstractEventExecutor {
             if (state == ST_NOT_STARTED) {
                 state = ST_STARTED;
                 delayedTaskQueue.add(new ScheduledFutureTask<Void>(
-                        this, Executors.<Void>callable(new PurgeTask(), null),
-                        deadlineNanos(SCHEDULE_PURGE_INTERVAL), -SCHEDULE_PURGE_INTERVAL));
+                        this, delayedTaskQueue, Executors.<Void>callable(new PurgeTask(), null),
+                        ScheduledFutureTask.deadlineNanos(SCHEDULE_PURGE_INTERVAL), -SCHEDULE_PURGE_INTERVAL));
                 thread.start();
             }
         }
     }
 
-    @SuppressWarnings("ComparableImplementedButEqualsNotOverridden")
-    private static final class ScheduledFutureTask<V> extends PromiseTask<V> implements ScheduledFuture<V> {
-
-        private final long id = nextTaskId.getAndIncrement();
-        private long deadlineNanos;
-        /* 0 - no repeat, >0 - repeat at fixed rate, <0 - repeat with fixed delay */
-        private final long periodNanos;
-
-        ScheduledFutureTask(SingleThreadEventExecutor executor, Runnable runnable, V result, long nanoTime) {
-            this(executor, Executors.callable(runnable, result), nanoTime);
-        }
-
-        ScheduledFutureTask(SingleThreadEventExecutor executor, Callable<V> callable, long nanoTime, long period) {
-            super(executor, callable);
-            if (period == 0) {
-                throw new IllegalArgumentException("period: 0 (expected: != 0)");
-            }
-            deadlineNanos = nanoTime;
-            periodNanos = period;
-        }
-
-        ScheduledFutureTask(SingleThreadEventExecutor executor, Callable<V> callable, long nanoTime) {
-            super(executor, callable);
-            deadlineNanos = nanoTime;
-            periodNanos = 0;
-        }
-
-        @Override
-        protected SingleThreadEventExecutor executor() {
-            return (SingleThreadEventExecutor) super.executor();
-        }
-
-        public long deadlineNanos() {
-            return deadlineNanos;
-        }
-
-        public long delayNanos() {
-            return Math.max(0, deadlineNanos() - nanoTime());
-        }
-
-        public long delayNanos(long currentTimeNanos) {
-            return Math.max(0, deadlineNanos() - (currentTimeNanos - START_TIME));
-        }
-
-        @Override
-        public long getDelay(TimeUnit unit) {
-            return unit.convert(delayNanos(), TimeUnit.NANOSECONDS);
-        }
-
-        @Override
-        public int compareTo(Delayed o) {
-            if (this == o) {
-                return 0;
-            }
-
-            ScheduledFutureTask<?> that = (ScheduledFutureTask<?>) o;
-            long d = deadlineNanos() - that.deadlineNanos();
-            if (d < 0) {
-                return -1;
-            } else if (d > 0) {
-                return 1;
-            } else if (id < that.id) {
-                return -1;
-            } else if (id == that.id) {
-                throw new Error();
-            } else {
-                return 1;
-            }
-        }
-
-        @Override
-        public void run() {
-            assert executor().inEventLoop();
-            try {
-                if (periodNanos == 0) {
-                    if (setUncancellableInternal()) {
-                        V result = task.call();
-                        setSuccessInternal(result);
-                    }
-                } else {
-                    // check if is done as it may was cancelled
-                    if (!isCancelled()) {
-                        task.call();
-                        if (!executor().isShutdown()) {
-                            long p = periodNanos;
-                            if (p > 0) {
-                                deadlineNanos += p;
-                            } else {
-                                deadlineNanos = nanoTime() - p;
-                            }
-                            if (!isCancelled()) {
-                                executor().delayedTaskQueue.add(this);
-                            }
-                        }
-                    }
-                }
-            } catch (Throwable cause) {
-                setFailureInternal(cause);
-            }
-        }
-    }
-
     private final class PurgeTask implements Runnable {
         @Override
         public void run() {

common/src/test/java/io/netty/util/concurrent/GlobalEventExecutorTest.java

@@ -0,0 +1,112 @@
+/*
+ * Copyright 2013 The Netty Project
+ *
+ * The Netty Project licenses this file to you under the Apache License,
+ * version 2.0 (the "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at:
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ */
+
+package io.netty.util.concurrent;
+
+import org.junit.Before;
+import org.junit.Test;
+
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicBoolean;
+
+import static org.hamcrest.CoreMatchers.*;
+import static org.junit.Assert.*;
+
+public class GlobalEventExecutorTest {
+
+    private static final GlobalEventExecutor e = GlobalEventExecutor.INSTANCE;
+
+    @Before
+    public void setUp() throws Exception {
+        // Wait until the global executor is stopped (just in case there is a task running due to previous test cases)
+        for (;;) {
+            if (e.thread == null || !e.thread.isAlive()) {
+                break;
+            }
+
+            Thread.sleep(50);
+        }
+    }
+
+    @Test
+    public void testAutomaticStartStop() throws Exception {
+        final TestRunnable task = new TestRunnable(500);
+        e.execute(task);
+
+        // Ensure the new thread has started.
+        Thread thread = e.thread;
+        assertThat(thread, is(not(nullValue())));
+        assertThat(thread.isAlive(), is(true));
+
+        Thread.sleep(1500);
+
+        // Ensure the thread stopped itself after running the task.
+        assertThat(thread.isAlive(), is(false));
+        assertThat(task.ran.get(), is(true));
+        assertThat(e.thread, sameInstance(thread));
+
+        // Ensure another new thread starts again.
+        task.ran.set(false);
+        e.execute(task);
+        assertThat(e.thread, not(sameInstance(thread)));
+        thread = e.thread;
+
+        Thread.sleep(1500);
+
+        // Ensure the thread stopped itself after running the task.
+        assertThat(thread.isAlive(), is(false));
+        assertThat(task.ran.get(), is(true));
+        assertThat(e.thread, sameInstance(thread));
+    }
+
+    @Test
+    public void testScheduledTasks() throws Exception {
+        TestRunnable task = new TestRunnable(0);
+        ScheduledFuture<?> f = e.schedule(task, 1500, TimeUnit.MILLISECONDS);
+        f.sync();
+        assertThat(task.ran.get(), is(true));
+
+        // Ensure the thread is still running.
+        Thread thread = e.thread;
+        assertThat(thread, is(not(nullValue())));
+        assertThat(thread.isAlive(), is(true));
+
+        Thread.sleep(1500);
+
+        // Not it should be stopped.
+        assertThat(thread.isAlive(), is(false));
+        assertThat(e.thread, sameInstance(thread));
+    }
+
+    private static final class TestRunnable implements Runnable {
+        final AtomicBoolean ran = new AtomicBoolean();
+        final long delay;
+
+        TestRunnable(long delay) {
+            this.delay = delay;
+        }
+
+        @Override
+        public void run() {
+            try {
+                Thread.sleep(delay);
+                ran.set(true);
+            } catch (InterruptedException ignored) {
+                // Ignore
+            }
+        }
+    }
+}