/*
    * 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:
    *
    * https://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.netty5.handler.traffic;
  
  import io.netty5.channel.Channel;
  import io.netty5.channel.ChannelHandlerContext;
  import io.netty5.channel.ChannelOption;
  import io.netty5.util.Attribute;
  import io.netty5.util.Resource;
  import io.netty5.util.concurrent.EventExecutor;
  import io.netty5.util.concurrent.EventExecutorGroup;
  import io.netty5.util.concurrent.Future;
  import io.netty5.util.concurrent.Promise;
  import io.netty5.util.internal.logging.InternalLogger;
  import io.netty5.util.internal.logging.InternalLoggerFactory;
  
  import java.util.AbstractCollection;
  import java.util.ArrayDeque;
  import java.util.Collection;
  import java.util.Iterator;
  import java.util.concurrent.ConcurrentHashMap;
  import java.util.concurrent.ConcurrentMap;
  import java.util.concurrent.TimeUnit;
  import java.util.concurrent.atomic.AtomicLong;
  
  import static io.netty5.util.internal.ObjectUtil.checkNotNullWithIAE;
  import static io.netty5.util.internal.ObjectUtil.checkPositive;
  import static io.netty5.util.internal.ObjectUtil.checkPositiveOrZero;
  
  /**
   * This implementation of the {@link AbstractTrafficShapingHandler} is for global
   * and per channel traffic shaping, that is to say a global limitation of the bandwidth, whatever
   * the number of opened channels and a per channel limitation of the bandwidth.<br><br>
   * This version shall not be in the same pipeline than other TrafficShapingHandler.<br><br>
   *
   * The general use should be as follow:<br>
   * <ul>
   * <li>Create your unique GlobalChannelTrafficShapingHandler like:<br><br>
   * <tt>GlobalChannelTrafficShapingHandler myHandler = new GlobalChannelTrafficShapingHandler(executor);</tt><br><br>
   * The executor could be the underlying IO worker pool<br>
   * <tt>pipeline.addLast(myHandler);</tt><br><br>
   *
   * <b>Note that this handler has a Pipeline Coverage of "all" which means only one such handler must be created
   * and shared among all channels as the counter must be shared among all channels.</b><br><br>
   *
   * Other arguments can be passed like write or read limitation (in bytes/s where 0 means no limitation)
   * or the check interval (in millisecond) that represents the delay between two computations of the
   * bandwidth and so the call back of the doAccounting method (0 means no accounting at all).<br>
   * Note that as this is a fusion of both Global and Channel Traffic Shaping, limits are in 2 sets,
   * respectively Global and Channel.<br><br>
   *
   * A value of 0 means no accounting for checkInterval. If you need traffic shaping but no such accounting,
   * it is recommended to set a positive value, even if it is high since the precision of the
   * Traffic Shaping depends on the period where the traffic is computed. The highest the interval,
   * the less precise the traffic shaping will be. It is suggested as higher value something close
   * to 5 or 10 minutes.<br><br>
   *
   * maxTimeToWait, by default set to 15s, allows to specify an upper bound of time shaping.<br><br>
   * </li>
   * <li>In your handler, you should consider to use the {@code channel.isWritable()} and
   * {@code channelWritabilityChanged(ctx)} to handle writability, or through
   * {@code future.addListener(future -> ...)} on the future returned by
   * {@code ctx.write()}.</li>
   * <li>You shall also consider to have object size in read or write operations relatively adapted to
   * the bandwidth you required: for instance having 10 MB objects for 10KB/s will lead to burst effect,
   * while having 100 KB objects for 1 MB/s should be smoothly handle by this TrafficShaping handler.<br><br></li>
   * <li>Some configuration methods will be taken as best effort, meaning
   * that all already scheduled traffics will not be
   * changed, but only applied to new traffics.<br>
   * So the expected usage of those methods are to be used not too often,
   * accordingly to the traffic shaping configuration.</li>
   * </ul><br>
   *
   * Be sure to call {@link #release()} once this handler is not needed anymore to release all internal resources.
   * This will not shutdown the {@link EventExecutor} as it may be shared, so you need to do this by your own.
   */
  public class GlobalChannelTrafficShapingHandler extends AbstractTrafficShapingHandler {
      private static final InternalLogger logger =
              InternalLoggerFactory.getInstance(GlobalChannelTrafficShapingHandler.class);
      /**
       * All queues per channel
       */
      final ConcurrentMap<Integer, PerChannel> channelQueues = new ConcurrentHashMap<>();
  
      /**
       * Global queues size
      */
     private final AtomicLong queuesSize = new AtomicLong();
 
     /**
      * Maximum cumulative writing bytes for one channel among all (as long as channels stay the same)
      */
     private final AtomicLong cumulativeWrittenBytes = new AtomicLong();
 
     /**
      * Maximum cumulative read bytes for one channel among all (as long as channels stay the same)
      */
     private final AtomicLong cumulativeReadBytes = new AtomicLong();
 
     /**
      * Max size in the list before proposing to stop writing new objects from next handlers
      * for all channel (global)
      */
     volatile long maxGlobalWriteSize = DEFAULT_MAX_SIZE * 100; // default 400MB
 
     /**
      * Limit in B/s to apply to write
      */
     private volatile long writeChannelLimit;
 
     /**
      * Limit in B/s to apply to read
      */
     private volatile long readChannelLimit;
 
     private static final float DEFAULT_DEVIATION = 0.1F;
     private static final float MAX_DEVIATION = 0.4F;
     private static final float DEFAULT_SLOWDOWN = 0.4F;
     private static final float DEFAULT_ACCELERATION = -0.1F;
     private volatile float maxDeviation;
     private volatile float accelerationFactor;
     private volatile float slowDownFactor;
     private volatile boolean readDeviationActive;
     private volatile boolean writeDeviationActive;
 
     static final class PerChannel {
         ArrayDeque<ToSend> messagesQueue;
         TrafficCounter channelTrafficCounter;
         long queueSize;
         long lastWriteTimestamp;
         long lastReadTimestamp;
     }
 
     /**
      * Create the global TrafficCounter
      */
     void createGlobalTrafficCounter(EventExecutorGroup executor) {
         // Default
         setMaxDeviation(DEFAULT_DEVIATION, DEFAULT_SLOWDOWN, DEFAULT_ACCELERATION);
         checkNotNullWithIAE(executor, "executor");
         TrafficCounter tc = new GlobalChannelTrafficCounter(this, executor, "GlobalChannelTC", checkInterval);
         setTrafficCounter(tc);
         tc.start();
     }
 
     @Override
     protected int userDefinedWritabilityIndex() {
         return AbstractTrafficShapingHandler.GLOBALCHANNEL_DEFAULT_USER_DEFINED_WRITABILITY_INDEX;
     }
 
     /**
      * Create a new instance.
      *
      * @param executor
      *            the {@link EventExecutorGroup} to use for the {@link TrafficCounter}.
      * @param writeGlobalLimit
      *            0 or a limit in bytes/s
      * @param readGlobalLimit
      *            0 or a limit in bytes/s
      * @param writeChannelLimit
      *            0 or a limit in bytes/s
      * @param readChannelLimit
      *            0 or a limit in bytes/s
      * @param checkInterval
      *            The delay between two computations of performances for
      *            channels or 0 if no stats are to be computed.
      * @param maxTime
      *            The maximum delay to wait in case of traffic excess.
      */
     public GlobalChannelTrafficShapingHandler(EventExecutorGroup executor,
             long writeGlobalLimit, long readGlobalLimit,
             long writeChannelLimit, long readChannelLimit,
             long checkInterval, long maxTime) {
         super(writeGlobalLimit, readGlobalLimit, checkInterval, maxTime);
         createGlobalTrafficCounter(executor);
         this.writeChannelLimit = writeChannelLimit;
         this.readChannelLimit = readChannelLimit;
     }
 
     /**
      * Create a new instance.
      *
      * @param executor
      *          the {@link EventExecutorGroup} to use for the {@link TrafficCounter}.
      * @param writeGlobalLimit
      *            0 or a limit in bytes/s
      * @param readGlobalLimit
      *            0 or a limit in bytes/s
      * @param writeChannelLimit
      *            0 or a limit in bytes/s
      * @param readChannelLimit
      *            0 or a limit in bytes/s
      * @param checkInterval
      *          The delay between two computations of performances for
      *            channels or 0 if no stats are to be computed.
      */
     public GlobalChannelTrafficShapingHandler(EventExecutorGroup executor,
             long writeGlobalLimit, long readGlobalLimit,
             long writeChannelLimit, long readChannelLimit,
             long checkInterval) {
         super(writeGlobalLimit, readGlobalLimit, checkInterval);
         this.writeChannelLimit = writeChannelLimit;
         this.readChannelLimit = readChannelLimit;
         createGlobalTrafficCounter(executor);
     }
 
     /**
      * Create a new instance.
      *
      * @param executor
      *          the {@link EventExecutorGroup} to use for the {@link TrafficCounter}.
      * @param writeGlobalLimit
      *            0 or a limit in bytes/s
      * @param readGlobalLimit
      *            0 or a limit in bytes/s
      * @param writeChannelLimit
      *            0 or a limit in bytes/s
      * @param readChannelLimit
      *            0 or a limit in bytes/s
      */
     public GlobalChannelTrafficShapingHandler(EventExecutorGroup executor,
             long writeGlobalLimit, long readGlobalLimit,
             long writeChannelLimit, long readChannelLimit) {
         super(writeGlobalLimit, readGlobalLimit);
         this.writeChannelLimit = writeChannelLimit;
         this.readChannelLimit = readChannelLimit;
         createGlobalTrafficCounter(executor);
     }
 
     /**
      * Create a new instance.
      *
      * @param executor
      *          the {@link EventExecutorGroup} to use for the {@link TrafficCounter}.
      * @param checkInterval
      *          The delay between two computations of performances for
      *            channels or 0 if no stats are to be computed.
      */
     public GlobalChannelTrafficShapingHandler(EventExecutorGroup executor, long checkInterval) {
         super(checkInterval);
         createGlobalTrafficCounter(executor);
     }
 
     /**
      * Create a new instance.
      *
      * @param executor
      *          the {@link EventExecutorGroup} to use for the {@link TrafficCounter}.
      */
     public GlobalChannelTrafficShapingHandler(EventExecutorGroup executor) {
         createGlobalTrafficCounter(executor);
     }
 
     @Override
     public boolean isSharable() {
         return true;
     }
 
     /**
      * @return the current max deviation
      */
     public float maxDeviation() {
         return maxDeviation;
     }
 
     /**
      * @return the current acceleration factor
      */
     public float accelerationFactor() {
         return accelerationFactor;
     }
 
     /**
      * @return the current slow down factor
      */
     public float slowDownFactor() {
         return slowDownFactor;
     }
 
     /**
      * @param maxDeviation
      *            the maximum deviation to allow during computation of average, default deviation
      *            being 0.1, so +/-10% of the desired bandwidth. Maximum being 0.4.
      * @param slowDownFactor
      *            the factor set as +x% to the too fast client (minimal value being 0, meaning no
      *            slow down factor), default being 40% (0.4).
      * @param accelerationFactor
      *            the factor set as -x% to the too slow client (maximal value being 0, meaning no
      *            acceleration factor), default being -10% (-0.1).
      */
     public void setMaxDeviation(float maxDeviation, float slowDownFactor, float accelerationFactor) {
         if (maxDeviation > MAX_DEVIATION) {
             throw new IllegalArgumentException("maxDeviation must be <= " + MAX_DEVIATION);
         }
         checkPositiveOrZero(slowDownFactor, "slowDownFactor");
         if (accelerationFactor > 0) {
             throw new IllegalArgumentException("accelerationFactor must be <= 0");
         }
         this.maxDeviation = maxDeviation;
         this.accelerationFactor = 1 + accelerationFactor;
         this.slowDownFactor = 1 + slowDownFactor;
     }
 
     private void computeDeviationCumulativeBytes() {
         // compute the maximum cumulativeXxxxBytes among still connected Channels
         long maxWrittenBytes = 0;
         long maxReadBytes = 0;
         long minWrittenBytes = Long.MAX_VALUE;
         long minReadBytes = Long.MAX_VALUE;
         for (PerChannel perChannel : channelQueues.values()) {
             long value = perChannel.channelTrafficCounter.cumulativeWrittenBytes();
             if (maxWrittenBytes < value) {
                 maxWrittenBytes = value;
             }
             if (minWrittenBytes > value) {
                 minWrittenBytes = value;
             }
             value = perChannel.channelTrafficCounter.cumulativeReadBytes();
             if (maxReadBytes < value) {
                 maxReadBytes = value;
             }
             if (minReadBytes > value) {
                 minReadBytes = value;
             }
         }
         boolean multiple = channelQueues.size() > 1;
         readDeviationActive = multiple && minReadBytes < maxReadBytes / 2;
         writeDeviationActive = multiple && minWrittenBytes < maxWrittenBytes / 2;
         cumulativeWrittenBytes.set(maxWrittenBytes);
         cumulativeReadBytes.set(maxReadBytes);
     }
 
     @Override
     protected void doAccounting(TrafficCounter counter) {
         computeDeviationCumulativeBytes();
         super.doAccounting(counter);
     }
 
     private long computeBalancedWait(float maxLocal, float maxGlobal, long wait) {
         if (maxGlobal == 0) {
             // no change
             return wait;
         }
         float ratio = maxLocal / maxGlobal;
         // if in the boundaries, same value
         if (ratio > maxDeviation) {
             if (ratio < 1 - maxDeviation) {
                 return wait;
             } else {
                 ratio = slowDownFactor;
                 if (wait < MINIMAL_WAIT) {
                     wait = MINIMAL_WAIT;
                 }
             }
         } else {
             ratio = accelerationFactor;
         }
         return (long) (wait * ratio);
     }
 
     /**
      * @return the maxGlobalWriteSize
      */
     public long getMaxGlobalWriteSize() {
         return maxGlobalWriteSize;
     }
 
     /**
      * Note the change will be taken as best effort, meaning
      * that all already scheduled traffics will not be
      * changed, but only applied to new traffics.<br>
      * So the expected usage of this method is to be used not too often,
      * accordingly to the traffic shaping configuration.
      *
      * @param maxGlobalWriteSize the maximum Global Write Size allowed in the buffer
      *            globally for all channels before write suspended is set.
      */
     public void setMaxGlobalWriteSize(long maxGlobalWriteSize) {
         this.maxGlobalWriteSize = checkPositive(maxGlobalWriteSize, "maxGlobalWriteSize");
     }
 
     /**
      * @return the global size of the buffers for all queues.
      */
     public long queuesSize() {
         return queuesSize.get();
     }
 
     /**
      * @param newWriteLimit Channel write limit
      * @param newReadLimit Channel read limit
      */
     public void configureChannel(long newWriteLimit, long newReadLimit) {
         writeChannelLimit = newWriteLimit;
         readChannelLimit = newReadLimit;
         long now = TrafficCounter.milliSecondFromNano();
         for (PerChannel perChannel : channelQueues.values()) {
             perChannel.channelTrafficCounter.resetAccounting(now);
         }
     }
 
     /**
      * @return Channel write limit
      */
     public long getWriteChannelLimit() {
         return writeChannelLimit;
     }
 
     /**
      * @param writeLimit Channel write limit
      */
     public void setWriteChannelLimit(long writeLimit) {
         writeChannelLimit = writeLimit;
         long now = TrafficCounter.milliSecondFromNano();
         for (PerChannel perChannel : channelQueues.values()) {
             perChannel.channelTrafficCounter.resetAccounting(now);
         }
     }
 
     /**
      * @return Channel read limit
      */
     public long getReadChannelLimit() {
         return readChannelLimit;
     }
 
     /**
      * @param readLimit Channel read limit
      */
     public void setReadChannelLimit(long readLimit) {
         readChannelLimit = readLimit;
         long now = TrafficCounter.milliSecondFromNano();
         for (PerChannel perChannel : channelQueues.values()) {
             perChannel.channelTrafficCounter.resetAccounting(now);
         }
     }
 
     /**
      * Release all internal resources of this instance.
      */
     public final void release() {
         trafficCounter.stop();
     }
 
     private PerChannel getOrSetPerChannel(ChannelHandlerContext ctx) {
         // ensure creation is limited to one thread per channel
         Channel channel = ctx.channel();
         Integer key = channel.hashCode();
         PerChannel perChannel = channelQueues.get(key);
         if (perChannel == null) {
             perChannel = new PerChannel();
             perChannel.messagesQueue = new ArrayDeque<>();
             // Don't start it since managed through the Global one
             perChannel.channelTrafficCounter = new TrafficCounter(this, null, "ChannelTC" +
                     ctx.channel().hashCode(), checkInterval);
             perChannel.queueSize = 0L;
             perChannel.lastReadTimestamp = TrafficCounter.milliSecondFromNano();
             perChannel.lastWriteTimestamp = perChannel.lastReadTimestamp;
             channelQueues.put(key, perChannel);
         }
         return perChannel;
     }
 
     @Override
     public void handlerAdded(ChannelHandlerContext ctx) throws Exception {
         getOrSetPerChannel(ctx);
         trafficCounter.resetCumulativeTime();
         super.handlerAdded(ctx);
     }
 
     @Override
     public void handlerRemoved(ChannelHandlerContext ctx) throws Exception {
         trafficCounter.resetCumulativeTime();
         Channel channel = ctx.channel();
         Integer key = channel.hashCode();
         PerChannel perChannel = channelQueues.remove(key);
         if (perChannel != null) {
             // write operations need synchronization
             synchronized (perChannel) {
                 if (channel.isActive()) {
                     for (ToSend toSend : perChannel.messagesQueue) {
                         long size = calculateSize(toSend.toSend);
                         trafficCounter.bytesRealWriteFlowControl(size);
                         perChannel.channelTrafficCounter.bytesRealWriteFlowControl(size);
                         perChannel.queueSize -= size;
                         queuesSize.addAndGet(-size);
                         ctx.write(toSend.toSend).cascadeTo(toSend.promise);
                     }
                 } else {
                     queuesSize.addAndGet(-perChannel.queueSize);
                     for (ToSend toSend : perChannel.messagesQueue) {
                         if (Resource.isAccessible(toSend.toSend, false)) {
                             Resource.dispose(toSend.toSend);
                         }
                     }
                 }
                 perChannel.messagesQueue.clear();
             }
         }
         releaseWriteSuspended(ctx);
         releaseReadSuspended(ctx);
         super.handlerRemoved(ctx);
     }
 
     @Override
     public void channelRead(final ChannelHandlerContext ctx, final Object msg) throws Exception {
         long size = calculateSize(msg);
         long now = TrafficCounter.milliSecondFromNano();
         if (size > 0) {
             // compute the number of ms to wait before reopening the channel
             long waitGlobal = trafficCounter.readTimeToWait(size, getReadLimit(), maxTime, now);
             Integer key = ctx.channel().hashCode();
             PerChannel perChannel = channelQueues.get(key);
             long wait = 0;
             if (perChannel != null) {
                 wait = perChannel.channelTrafficCounter.readTimeToWait(size, readChannelLimit, maxTime, now);
                 if (readDeviationActive) {
                     // now try to balance between the channels
                     long maxLocalRead;
                     maxLocalRead = perChannel.channelTrafficCounter.cumulativeReadBytes();
                     long maxGlobalRead = cumulativeReadBytes.get();
                     if (maxLocalRead <= 0) {
                         maxLocalRead = 0;
                     }
                     if (maxGlobalRead < maxLocalRead) {
                         maxGlobalRead = maxLocalRead;
                     }
                     wait = computeBalancedWait(maxLocalRead, maxGlobalRead, wait);
                 }
             }
             if (wait < waitGlobal) {
                 wait = waitGlobal;
             }
             wait = checkWaitReadTime(ctx, wait, now);
             if (wait >= MINIMAL_WAIT) { // At least 10ms seems a minimal
                 // time in order to try to limit the traffic
                 // Only AutoRead AND HandlerActive True means Context Active
                 Channel channel = ctx.channel();
                 if (logger.isDebugEnabled()) {
                     logger.debug("Read Suspend: " + wait + ':' + channel.getOption(ChannelOption.AUTO_READ) + ':'
                             + isHandlerActive(ctx));
                 }
                 if (channel.getOption(ChannelOption.AUTO_READ) && isHandlerActive(ctx)) {
                     channel.setOption(ChannelOption.AUTO_READ, false);
                     channel.attr(READ_SUSPENDED).set(true);
                     // Create a Runnable to reactive the read if needed. If one was create before it will just be
                     // reused to limit object creation
                     Attribute<Runnable> attr = channel.attr(REOPEN_TASK);
                     Runnable reopenTask = attr.get();
                     if (reopenTask == null) {
                         reopenTask = new ReopenReadTimerTask(ctx);
                         attr.set(reopenTask);
                     }
                     ctx.executor().schedule(reopenTask, wait, TimeUnit.MILLISECONDS);
                     if (logger.isDebugEnabled()) {
                         logger.debug("Suspend final status => " + channel.getOption(ChannelOption.AUTO_READ) + ':'
                                 + isHandlerActive(ctx) + " will reopened at: " + wait);
                     }
                 }
             }
         }
         informReadOperation(ctx, now);
         ctx.fireChannelRead(msg);
     }
 
     @Override
     protected long checkWaitReadTime(final ChannelHandlerContext ctx, long wait, final long now) {
         Integer key = ctx.channel().hashCode();
         PerChannel perChannel = channelQueues.get(key);
         if (perChannel != null) {
             if (wait > maxTime && now + wait - perChannel.lastReadTimestamp > maxTime) {
                 wait = maxTime;
             }
         }
         return wait;
     }
 
     @Override
     protected void informReadOperation(final ChannelHandlerContext ctx, final long now) {
         Integer key = ctx.channel().hashCode();
         PerChannel perChannel = channelQueues.get(key);
         if (perChannel != null) {
             perChannel.lastReadTimestamp = now;
         }
     }
 
     private static final class ToSend {
         final long relativeTimeAction;
         final Object toSend;
         final Promise<Void> promise;
         final long size;
 
         private ToSend(final long delay, final Object toSend, final long size, final Promise<Void> promise) {
             relativeTimeAction = delay;
             this.toSend = toSend;
             this.size = size;
             this.promise = promise;
         }
     }
 
     protected long maximumCumulativeWrittenBytes() {
         return cumulativeWrittenBytes.get();
     }
 
     protected long maximumCumulativeReadBytes() {
         return cumulativeReadBytes.get();
     }
 
     /**
      * To allow for instance doAccounting to use the TrafficCounter per channel.
      * @return the list of TrafficCounters that exists at the time of the call.
      */
     public Collection<TrafficCounter> channelTrafficCounters() {
         return new AbstractCollection<>() {
             @Override
             public Iterator<TrafficCounter> iterator() {
                 return new Iterator<>() {
                     final Iterator<PerChannel> iter = channelQueues.values().iterator();
 
                     @Override
                     public boolean hasNext() {
                         return iter.hasNext();
                     }
 
                     @Override
                     public TrafficCounter next() {
                         return iter.next().channelTrafficCounter;
                     }
 
                     @Override
                     public void remove() {
                         throw new UnsupportedOperationException();
                     }
                 };
             }
 
             @Override
             public int size() {
                 return channelQueues.size();
             }
         };
     }
 
     @Override
     public Future<Void> write(final ChannelHandlerContext ctx, final Object msg) {
         long size = calculateSize(msg);
         long now = TrafficCounter.milliSecondFromNano();
         if (size > 0) {
             // compute the number of ms to wait before continue with the channel
             long waitGlobal = trafficCounter.writeTimeToWait(size, getWriteLimit(), maxTime, now);
             Integer key = ctx.channel().hashCode();
             PerChannel perChannel = channelQueues.get(key);
             long wait = 0;
             if (perChannel != null) {
                 wait = perChannel.channelTrafficCounter.writeTimeToWait(size, writeChannelLimit, maxTime, now);
                 if (writeDeviationActive) {
                     // now try to balance between the channels
                     long maxLocalWrite;
                     maxLocalWrite = perChannel.channelTrafficCounter.cumulativeWrittenBytes();
                     long maxGlobalWrite = cumulativeWrittenBytes.get();
                     if (maxLocalWrite <= 0) {
                         maxLocalWrite = 0;
                     }
                     if (maxGlobalWrite < maxLocalWrite) {
                         maxGlobalWrite = maxLocalWrite;
                     }
                     wait = computeBalancedWait(maxLocalWrite, maxGlobalWrite, wait);
                 }
             }
             if (wait < waitGlobal) {
                 wait = waitGlobal;
             }
             if (wait >= MINIMAL_WAIT) {
                 if (logger.isDebugEnabled()) {
                     logger.debug("Write suspend: " + wait + ':' + ctx.channel().getOption(ChannelOption.AUTO_READ) + ':'
                             + isHandlerActive(ctx));
                 }
                 Promise<Void> promise = ctx.newPromise();
                 submitWrite(ctx, msg, size, wait, now, promise);
                 return promise.asFuture();
             }
         }
         Promise<Void> promise = ctx.newPromise();
         // to maintain order of write
         submitWrite(ctx, msg, size, 0, now, promise);
         return promise.asFuture();
     }
 
     @Override
     protected void submitWrite(final ChannelHandlerContext ctx, final Object msg,
             final long size, final long writedelay, final long now,
             final Promise<Void> promise) {
         Channel channel = ctx.channel();
         Integer key = channel.hashCode();
         PerChannel perChannel = channelQueues.get(key);
         if (perChannel == null) {
             // in case write occurs before handlerAdded is raised for this handler
             // imply a synchronized only if needed
             perChannel = getOrSetPerChannel(ctx);
         }
         final ToSend newToSend;
         long delay = writedelay;
         boolean globalSizeExceeded = false;
         // write operations need synchronization
         synchronized (perChannel) {
             if (writedelay == 0 && perChannel.messagesQueue.isEmpty()) {
                 trafficCounter.bytesRealWriteFlowControl(size);
                 perChannel.channelTrafficCounter.bytesRealWriteFlowControl(size);
                 ctx.write(msg).cascadeTo(promise);
                 perChannel.lastWriteTimestamp = now;
                 return;
             }
             if (delay > maxTime && now + delay - perChannel.lastWriteTimestamp > maxTime) {
                 delay = maxTime;
             }
             newToSend = new ToSend(delay + now, msg, size, promise);
             perChannel.messagesQueue.addLast(newToSend);
             perChannel.queueSize += size;
             queuesSize.addAndGet(size);
             checkWriteSuspend(ctx, delay, perChannel.queueSize);
             if (queuesSize.get() > maxGlobalWriteSize) {
                 globalSizeExceeded = true;
             }
         }
         if (globalSizeExceeded) {
             setUserDefinedWritability(ctx, false);
         }
         final long futureNow = newToSend.relativeTimeAction;
         final PerChannel forSchedule = perChannel;
         ctx.executor().schedule(() -> sendAllValid(ctx, forSchedule, futureNow), delay, TimeUnit.MILLISECONDS);
     }
 
     private void sendAllValid(final ChannelHandlerContext ctx, final PerChannel perChannel, final long now) {
         // write operations need synchronization
         synchronized (perChannel) {
             ToSend newToSend = perChannel.messagesQueue.pollFirst();
             for (; newToSend != null; newToSend = perChannel.messagesQueue.pollFirst()) {
                 if (newToSend.relativeTimeAction <= now) {
                     long size = newToSend.size;
                     trafficCounter.bytesRealWriteFlowControl(size);
                     perChannel.channelTrafficCounter.bytesRealWriteFlowControl(size);
                     perChannel.queueSize -= size;
                     queuesSize.addAndGet(-size);
                     ctx.write(newToSend.toSend).cascadeTo(newToSend.promise);
                     perChannel.lastWriteTimestamp = now;
                 } else {
                     perChannel.messagesQueue.addFirst(newToSend);
                     break;
                 }
             }
             if (perChannel.messagesQueue.isEmpty()) {
                 releaseWriteSuspended(ctx);
             }
         }
         ctx.flush();
     }
 
     @Override
     public String toString() {
         return new StringBuilder(340).append(super.toString())
             .append(" Write Channel Limit: ").append(writeChannelLimit)
             .append(" Read Channel Limit: ").append(readChannelLimit).toString();
     }
 }