[#1259] Add optimized queue for SCMP pattern and use it in NIO and native transport

This queue also produces less GC then CLQ when make use of OneTimeTask

NOTICE.txt

@@ -119,3 +119,12 @@ by Google Inc, which can be obtained at:
     * license/LICENSE.snappy.txt (New BSD License)
   * HOMEPAGE:
     * http://code.google.com/p/snappy/
+
+This product contains a modified version of Roland Kuhn's ASL2
+AbstractNodeQueue, which is based on Dmitriy Vyukov's non-intrusive MPSC queue.
+It can be obtained at:
+
+  * LICENSE:
+    * license/LICENSE.abstractnodequeue.txt (Public Domain)
+  * HOMEPAGE:
+    * https://github.com/akka/akka/blob/wip-2.2.3-for-scala-2.11/akka-actor/src/main/java/akka/dispatch/AbstractNodeQueue.java

common/src/main/java/io/netty/util/internal/MpscLinkedQueue.java

@@ -0,0 +1,245 @@
+/*
+ * Copyright 2014 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.
+ */
+/**
+ * Copyright (C) 2009-2013 Typesafe Inc. <http://www.typesafe.com>
+ */
+package io.netty.util.internal;
+
+
+import java.util.Collection;
+import java.util.Iterator;
+import java.util.NoSuchElementException;
+import java.util.Queue;
+import java.util.concurrent.atomic.AtomicReference;
+
+/**
+ * A lock-free concurrent {@link java.util.Queue} implementations for single-consumer multiple-producer pattern.
+ * <strong>It's important is is only used for this as otherwise it is not thread-safe.</strong>
+ *
+ * This implementation is based on:
+ * <ul>
+ *   <li><a href="https://github.com/akka/akka/blob/wip-2.2.3-for-scala-2.11/akka-actor/src/main/java/akka/dispatch/
+ *   AbstractNodeQueue.java">AbstractNodeQueue</a></li>
+ *   <li><a href="http://www.1024cores.net/home/lock-free-algorithms/
+ *   queues/non-intrusive-mpsc-node-based-queue">Non intrusive MPSC node based queue</a></li>
+ * </ul>
+ *
+ */
+@SuppressWarnings("serial")
+final class MpscLinkedQueue extends AtomicReference<OneTimeTask> implements Queue<Runnable> {
+    private static final long tailOffset;
+
+    static {
+        try {
+            tailOffset = PlatformDependent.objectFieldOffset(
+                    MpscLinkedQueue.class.getDeclaredField("tail"));
+        } catch (Throwable t) {
+            throw new ExceptionInInitializerError(t);
+        }
+    }
+
+    // Extends AtomicReference for the "head" slot (which is the one that is appended to)
+    // since Unsafe does not expose XCHG operation intrinsically
+    @SuppressWarnings({ "unused", "FieldMayBeFinal" })
+    private volatile OneTimeTask tail;
+
+    MpscLinkedQueue() {
+        final OneTimeTask task = new OneTimeTaskAdapter(null);
+        tail = task;
+        set(task);
+    }
+
+    @Override
+    public boolean add(Runnable runnable) {
+        if (runnable instanceof OneTimeTask) {
+            OneTimeTask node = (OneTimeTask) runnable;
+            node.setNext(null);
+            getAndSet(node).setNext(node);
+        } else {
+            final OneTimeTask n = new OneTimeTaskAdapter(runnable);
+            getAndSet(n).setNext(n);
+        }
+        return true;
+    }
+
+    @Override
+    public boolean offer(Runnable runnable) {
+        return add(runnable);
+    }
+
+    @Override
+    public Runnable remove() {
+        Runnable task = poll();
+        if (task == null) {
+            throw new NoSuchElementException();
+        }
+        return task;
+    }
+
+    @Override
+    public Runnable poll() {
+        final OneTimeTask next = peekTask();
+        if (next == null) {
+            return null;
+        }
+        final OneTimeTask ret = next;
+        PlatformDependent.putOrderedObject(this, tailOffset, next);
+        return unwrapIfNeeded(ret);
+    }
+
+    @Override
+    public Runnable element() {
+        final OneTimeTask next = peekTask();
+        if (next == null) {
+            throw new NoSuchElementException();
+        }
+        return unwrapIfNeeded(next);
+    }
+
+    @Override
+    public Runnable peek() {
+        final OneTimeTask next = peekTask();
+        if (next == null) {
+            return null;
+        }
+        return unwrapIfNeeded(next);
+    }
+
+    @Override
+    public int size() {
+        int count = 0;
+        OneTimeTask n = peekTask();
+        for (;;) {
+            if (n == null) {
+                break;
+            }
+            count++;
+            n = n.next();
+        }
+        return count;
+    }
+
+    @SuppressWarnings("unchecked")
+    private OneTimeTask peekTask() {
+        for (;;) {
+            final OneTimeTask tail = (OneTimeTask) PlatformDependent.getObjectVolatile(this, tailOffset);
+            final OneTimeTask next = tail.next();
+            if (next != null || get() == tail) {
+                return next;
+            }
+        }
+    }
+
+    @Override
+    public boolean isEmpty() {
+        return peek() == null;
+    }
+
+    @Override
+    public boolean contains(Object o) {
+        OneTimeTask n = peekTask();
+        for (;;) {
+            if (n == null) {
+                break;
+            }
+            if (unwrapIfNeeded(n) == o) {
+                return true;
+            }
+            n = n.next();
+        }
+        return false;
+    }
+
+    @Override
+    public Iterator<Runnable> iterator() {
+        throw new UnsupportedOperationException();
+    }
+
+    @Override
+    public Object[] toArray() {
+        throw new UnsupportedOperationException();
+    }
+
+    @Override
+    public <T> T[] toArray(T[] a) {
+        throw new UnsupportedOperationException();
+    }
+
+    @Override
+    public boolean remove(Object o) {
+        return false;
+    }
+
+    @Override
+    public boolean containsAll(Collection<?> c) {
+        for (Object o: c) {
+            if (!contains(o)) {
+                return false;
+            }
+        }
+        return true;
+    }
+
+    @Override
+    public boolean addAll(Collection<? extends Runnable> c) {
+        for (Runnable r: c) {
+            add(r);
+        }
+        return false;
+    }
+
+    @Override
+    public boolean removeAll(Collection<?> c) {
+        return false;
+    }
+
+    @Override
+    public boolean retainAll(Collection<?> c) {
+        return false;
+    }
+
+    @Override
+    public void clear() {
+        for (;;) {
+            if (poll() == null) {
+                break;
+            }
+        }
+    }
+
+    /**
+     * Unwrap {@link OneTimeTask} if needed and so return the proper queued task.
+     */
+    private static Runnable unwrapIfNeeded(OneTimeTask task) {
+        if (task instanceof OneTimeTaskAdapter) {
+            return ((OneTimeTaskAdapter) task).task;
+        }
+        return task;
+    }
+
+    private static final class OneTimeTaskAdapter extends OneTimeTask {
+        private final Runnable task;
+
+        OneTimeTaskAdapter(Runnable task) {
+            this.task = task;
+        }
+
+        @Override
+        public void run() {
+            task.run();
+        }
+    }
+}

common/src/main/java/io/netty/util/internal/OneTimeTask.java

@@ -0,0 +1,56 @@
+/*
+ * Copyright 2014 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.internal;
+
+import io.netty.util.concurrent.EventExecutor;
+
+/**
+ * {@link Runnable} which represent a one time task which may allow the {@link EventExecutor} to reduce the amount of
+ * produced garbage when queue it for execution.
+ *
+ * <strong>It is important this will not be reused. After submitted it is not allowed to get submitted again!</strong>
+ */
+public abstract class OneTimeTask implements Runnable {
+
+    private static final long nextOffset;
+
+    static {
+        if (PlatformDependent0.hasUnsafe()) {
+            try {
+                nextOffset = PlatformDependent.objectFieldOffset(
+                        OneTimeTask.class.getDeclaredField("tail"));
+            } catch (Throwable t) {
+                throw new ExceptionInInitializerError(t);
+            }
+        } else {
+            nextOffset = -1;
+        }
+    }
+
+    @SuppressWarnings("unused")
+    private volatile OneTimeTask tail;
+
+    // Only use from MpscLinkedQueue and so we are sure Unsafe is present
+    @SuppressWarnings("unchecked")
+    final OneTimeTask next() {
+        return (OneTimeTask) PlatformDependent.getObjectVolatile(this, nextOffset);
+    }
+
+    // Only use from MpscLinkedQueue and so we are sure Unsafe is present
+    final void setNext(final OneTimeTask newNext) {
+        PlatformDependent.putOrderedObject(this, nextOffset, newNext);
+    }
+}

common/src/main/java/io/netty/util/internal/PlatformDependent.java

@@ -32,8 +32,10 @@ import java.nio.ByteBuffer;
 import java.util.List;
 import java.util.Locale;
 import java.util.Map;
+import java.util.Queue;
 import java.util.concurrent.BlockingQueue;
 import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ConcurrentLinkedQueue;
 import java.util.concurrent.ConcurrentMap;
 import java.util.concurrent.atomic.AtomicIntegerFieldUpdater;
 import java.util.concurrent.atomic.AtomicLongFieldUpdater;
@@ -266,6 +268,10 @@ public final class PlatformDependent {
         return PlatformDependent0.getObject(object, fieldOffset);
     }
 
+    public static Object getObjectVolatile(Object object, long fieldOffset) {
+        return PlatformDependent0.getObjectVolatile(object, fieldOffset);
+    }
+
     public static int getInt(Object object, long fieldOffset) {
         return PlatformDependent0.getInt(object, fieldOffset);
     }
@@ -290,6 +296,10 @@ public final class PlatformDependent {
         return PlatformDependent0.getLong(address);
     }
 
+    public static void putOrderedObject(Object object, long address, Object value) {
+        PlatformDependent0.putOrderedObject(object, address, value);
+    }
+
     public static void putByte(long address, byte value) {
         PlatformDependent0.putByte(address, value);
     }
@@ -369,6 +379,18 @@ public final class PlatformDependent {
         return null;
     }
 
+    /**
+     * Create a new {@link Queue} which is safe to use for multiple producers (different threads) and a single
+     * consumer (one thread!).
+     */
+    public static Queue<Runnable> newMpscQueue() {
+        if (hasUnsafe()) {
+            return new MpscLinkedQueue();
+        } else {
+            return new ConcurrentLinkedQueue<Runnable>();
+        }
+    }
+
     private static boolean isAndroid0() {
         boolean android;
         try {

common/src/main/java/io/netty/util/internal/PlatformDependent0.java

@@ -185,6 +185,10 @@ final class PlatformDependent0 {
         return UNSAFE.getObject(object, fieldOffset);
     }
 
+    static Object getObjectVolatile(Object object, long fieldOffset) {
+        return UNSAFE.getObjectVolatile(object, fieldOffset);
+    }
+
     static int getInt(Object object, long fieldOffset) {
         return UNSAFE.getInt(object, fieldOffset);
     }
@@ -251,6 +255,10 @@ final class PlatformDependent0 {
         }
     }
 
+    static void putOrderedObject(Object object, long address, Object value) {
+        UNSAFE.putOrderedObject(object, address, value);
+    }
+
     static void putByte(long address, byte value) {
         UNSAFE.putByte(address, value);
     }

license/LICENSE.abstractnodequeue.txt

@@ -0,0 +1,15 @@
+This software is licensed under the Apache 2 license, quoted below.
+
+Copyright 2009-2013 Typesafe Inc. [http://www.typesafe.com]
+
+Licensed 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.

transport-native-epoll/src/main/java/io/netty/channel/epoll/EpollEventLoop.java

@@ -29,7 +29,6 @@ import java.util.Collection;
 import java.util.HashMap;
 import java.util.Map;
 import java.util.Queue;
-import java.util.concurrent.ConcurrentLinkedQueue;
 import java.util.concurrent.ThreadFactory;
 import java.util.concurrent.atomic.AtomicIntegerFieldUpdater;
 
@@ -156,7 +155,7 @@ final class EpollEventLoop extends SingleThreadEventLoop {
     @Override
     protected Queue<Runnable> newTaskQueue() {
         // This event loop never calls takeTask()
-        return new ConcurrentLinkedQueue<Runnable>();
+        return PlatformDependent.newMpscQueue();
     }
 
     /**

transport/src/main/java/io/netty/channel/AbstractChannel.java

@@ -19,6 +19,7 @@ import io.netty.buffer.ByteBufAllocator;
 import io.netty.util.DefaultAttributeMap;
 import io.netty.util.ReferenceCountUtil;
 import io.netty.util.internal.EmptyArrays;
+import io.netty.util.internal.OneTimeTask;
 import io.netty.util.internal.PlatformDependent;
 import io.netty.util.internal.ThreadLocalRandom;
 import io.netty.util.internal.logging.InternalLogger;
@@ -412,7 +413,7 @@ public abstract class AbstractChannel extends DefaultAttributeMap implements Cha
                 register0(promise);
             } else {
                 try {
-                    eventLoop.execute(new Runnable() {
+                    eventLoop.execute(new OneTimeTask() {
                         @Override
                         public void run() {
                             register0(promise);
@@ -480,7 +481,7 @@ public abstract class AbstractChannel extends DefaultAttributeMap implements Cha
             }
 
             if (!wasActive && isActive()) {
-                invokeLater(new Runnable() {
+                invokeLater(new OneTimeTask() {
                     @Override
                     public void run() {
                         pipeline.fireChannelActive();
@@ -507,7 +508,7 @@ public abstract class AbstractChannel extends DefaultAttributeMap implements Cha
             }
 
             if (wasActive && !isActive()) {
-                invokeLater(new Runnable() {
+                invokeLater(new OneTimeTask() {
                     @Override
                     public void run() {
                         pipeline.fireChannelInactive();
@@ -526,7 +527,7 @@ public abstract class AbstractChannel extends DefaultAttributeMap implements Cha
             }
 
             if (inFlush0) {
-                invokeLater(new Runnable() {
+                invokeLater(new OneTimeTask() {
                     @Override
                     public void run() {
                         close(promise);
@@ -561,7 +562,7 @@ public abstract class AbstractChannel extends DefaultAttributeMap implements Cha
             } finally {
 
                 if (wasActive && !isActive()) {
-                    invokeLater(new Runnable() {
+                    invokeLater(new OneTimeTask() {
                         @Override
                         public void run() {
                             pipeline.fireChannelInactive();
@@ -600,7 +601,7 @@ public abstract class AbstractChannel extends DefaultAttributeMap implements Cha
             } finally {
                 if (registered) {
                     registered = false;
-                    invokeLater(new Runnable() {
+                    invokeLater(new OneTimeTask() {
                         @Override
                         public void run() {
                             pipeline.fireChannelUnregistered();
@@ -625,7 +626,7 @@ public abstract class AbstractChannel extends DefaultAttributeMap implements Cha
             try {
                 doBeginRead();
             } catch (final Exception e) {
-                invokeLater(new Runnable() {
+                invokeLater(new OneTimeTask() {
                     @Override
                     public void run() {
                         pipeline.fireExceptionCaught(e);

transport/src/main/java/io/netty/channel/DefaultChannelHandlerContext.java

@@ -22,6 +22,7 @@ import io.netty.util.Recycler;
 import io.netty.util.ReferenceCountUtil;
 import io.netty.util.concurrent.EventExecutor;
 import io.netty.util.concurrent.EventExecutorGroup;
+import io.netty.util.internal.OneTimeTask;
 import io.netty.util.internal.StringUtil;
 
 import java.net.SocketAddress;
@@ -150,7 +151,7 @@ final class DefaultChannelHandlerContext extends DefaultAttributeMap implements
         if (executor.inEventLoop()) {
             next.invokeChannelRegistered();
         } else {
-            executor.execute(new Runnable() {
+            executor.execute(new OneTimeTask() {
                 @Override
                 public void run() {
                     next.invokeChannelRegistered();
@@ -175,7 +176,7 @@ final class DefaultChannelHandlerContext extends DefaultAttributeMap implements
         if (executor.inEventLoop()) {
             next.invokeChannelUnregistered();
         } else {
-            executor.execute(new Runnable() {
+            executor.execute(new OneTimeTask() {
                 @Override
                 public void run() {
                     next.invokeChannelUnregistered();
@@ -200,7 +201,7 @@ final class DefaultChannelHandlerContext extends DefaultAttributeMap implements
         if (executor.inEventLoop()) {
             next.invokeChannelActive();
         } else {
-            executor.execute(new Runnable() {
+            executor.execute(new OneTimeTask() {
                 @Override
                 public void run() {
                     next.invokeChannelActive();
@@ -225,7 +226,7 @@ final class DefaultChannelHandlerContext extends DefaultAttributeMap implements
         if (executor.inEventLoop()) {
             next.invokeChannelInactive();
         } else {
-            executor.execute(new Runnable() {
+            executor.execute(new OneTimeTask() {
                 @Override
                 public void run() {
                     next.invokeChannelInactive();
@@ -256,7 +257,7 @@ final class DefaultChannelHandlerContext extends DefaultAttributeMap implements
             next.invokeExceptionCaught(cause);
         } else {
             try {
-                executor.execute(new Runnable() {
+                executor.execute(new OneTimeTask() {
                     @Override
                     public void run() {
                         next.invokeExceptionCaught(cause);
@@ -296,7 +297,7 @@ final class DefaultChannelHandlerContext extends DefaultAttributeMap implements
         if (executor.inEventLoop()) {
             next.invokeUserEventTriggered(event);
         } else {
-            executor.execute(new Runnable() {
+            executor.execute(new OneTimeTask() {
                 @Override
                 public void run() {
                     next.invokeUserEventTriggered(event);
@@ -325,7 +326,7 @@ final class DefaultChannelHandlerContext extends DefaultAttributeMap implements
         if (executor.inEventLoop()) {
             next.invokeChannelRead(msg);
         } else {
-            executor.execute(new Runnable() {
+            executor.execute(new OneTimeTask() {
                 @Override
                 public void run() {
                     next.invokeChannelRead(msg);
@@ -443,7 +444,7 @@ final class DefaultChannelHandlerContext extends DefaultAttributeMap implements
         if (executor.inEventLoop()) {
             next.invokeBind(localAddress, promise);
         } else {
-            safeExecute(executor, new Runnable() {
+            safeExecute(executor, new OneTimeTask() {
                 @Override
                 public void run() {
                     next.invokeBind(localAddress, promise);
@@ -481,7 +482,7 @@ final class DefaultChannelHandlerContext extends DefaultAttributeMap implements
         if (executor.inEventLoop()) {
             next.invokeConnect(remoteAddress, localAddress, promise);
         } else {
-            safeExecute(executor, new Runnable() {
+            safeExecute(executor, new OneTimeTask() {
                 @Override
                 public void run() {
                     next.invokeConnect(remoteAddress, localAddress, promise);
@@ -515,7 +516,7 @@ final class DefaultChannelHandlerContext extends DefaultAttributeMap implements
                 next.invokeDisconnect(promise);
             }
         } else {
-            safeExecute(executor, new Runnable() {
+            safeExecute(executor, new OneTimeTask() {
                 @Override
                 public void run() {
                     if (!channel().metadata().hasDisconnect()) {
@@ -547,7 +548,7 @@ final class DefaultChannelHandlerContext extends DefaultAttributeMap implements
         if (executor.inEventLoop()) {
             next.invokeClose(promise);
         } else {
-            safeExecute(executor, new Runnable() {
+            safeExecute(executor, new OneTimeTask() {
                 @Override
                 public void run() {
                     next.invokeClose(promise);
@@ -575,7 +576,7 @@ final class DefaultChannelHandlerContext extends DefaultAttributeMap implements
         if (executor.inEventLoop()) {
             next.invokeDeregister(promise);
         } else {
-            safeExecute(executor, new Runnable() {
+            safeExecute(executor, new OneTimeTask() {
                 @Override
                 public void run() {
                     next.invokeDeregister(promise);
@@ -870,7 +871,7 @@ final class DefaultChannelHandlerContext extends DefaultAttributeMap implements
         }
     }
 
-    abstract static class AbstractWriteTask implements Runnable {
+    abstract static class AbstractWriteTask extends OneTimeTask {
         private final Recycler.Handle handle;
 
         private DefaultChannelHandlerContext ctx;

transport/src/main/java/io/netty/channel/nio/AbstractNioChannel.java

@@ -23,6 +23,7 @@ import io.netty.channel.ChannelFutureListener;
 import io.netty.channel.ChannelPromise;
 import io.netty.channel.ConnectTimeoutException;
 import io.netty.channel.EventLoop;
+import io.netty.util.internal.OneTimeTask;
 import io.netty.util.internal.logging.InternalLogger;
 import io.netty.util.internal.logging.InternalLoggerFactory;
 
@@ -199,7 +200,7 @@ public abstract class AbstractNioChannel extends AbstractChannel {
                     // Schedule connect timeout.
                     int connectTimeoutMillis = config().getConnectTimeoutMillis();
                     if (connectTimeoutMillis > 0) {
-                        connectTimeoutFuture = eventLoop().schedule(new Runnable() {
+                        connectTimeoutFuture = eventLoop().schedule(new OneTimeTask() {
                             @Override
                             public void run() {
                                 ChannelPromise connectPromise = AbstractNioChannel.this.connectPromise;

transport/src/main/java/io/netty/channel/nio/NioEventLoop.java

@@ -21,6 +21,7 @@ import io.netty.channel.ChannelException;
 import io.netty.channel.EventLoopException;
 import io.netty.channel.SingleThreadEventLoop;
 import io.netty.channel.nio.AbstractNioChannel.NioUnsafe;
+import io.netty.util.internal.PlatformDependent;
 import io.netty.util.internal.SystemPropertyUtil;
 import io.netty.util.internal.logging.InternalLogger;
 import io.netty.util.internal.logging.InternalLoggerFactory;
@@ -38,7 +39,6 @@ import java.util.ConcurrentModificationException;
 import java.util.Iterator;
 import java.util.Queue;
 import java.util.Set;
-import java.util.concurrent.ConcurrentLinkedQueue;
 import java.util.concurrent.ThreadFactory;
 import java.util.concurrent.atomic.AtomicBoolean;
 
@@ -165,7 +165,7 @@ public final class NioEventLoop extends SingleThreadEventLoop {
     @Override
     protected Queue<Runnable> newTaskQueue() {
         // This event loop never calls takeTask()
-        return new ConcurrentLinkedQueue<Runnable>();
+        return PlatformDependent.newMpscQueue();
     }
 
     /**

transport/src/main/java/io/netty/channel/socket/nio/NioSocketChannel.java

@@ -28,6 +28,7 @@ import io.netty.channel.nio.AbstractNioByteChannel;
 import io.netty.channel.socket.DefaultSocketChannelConfig;
 import io.netty.channel.socket.ServerSocketChannel;
 import io.netty.channel.socket.SocketChannelConfig;
+import io.netty.util.internal.OneTimeTask;
 
 import java.io.IOException;
 import java.net.InetSocketAddress;
@@ -140,7 +141,7 @@ public class NioSocketChannel extends AbstractNioByteChannel implements io.netty
                 promise.setFailure(t);
             }
         } else {
-            loop.execute(new Runnable() {
+            loop.execute(new OneTimeTask() {
                 @Override
                 public void run() {
                     shutdownOutput(promise);