ChannelTrafficShapingHandler.java — netty Source File

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/*
 * 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:
 *
 * 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.netty.handler.traffic;

import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelPromise;

import java.util.ArrayDeque;
import java.util.concurrent.TimeUnit;

/**
 * <p>This implementation of the {@link AbstractTrafficShapingHandler} is for channel
 * traffic shaping, that is to say a per channel limitation of the bandwidth.</p>
 * <p>Note the index used in {@code OutboundBuffer.setUserDefinedWritability(index, boolean)} is <b>1</b>.</p>
 *
 * <p>The general use should be as follow:</p>
 * <ul>
 * <li><p>Add in your pipeline a new ChannelTrafficShapingHandler.</p>
 * <p><tt>ChannelTrafficShapingHandler myHandler = new ChannelTrafficShapingHandler();</tt></p>
 * <p><tt>pipeline.addLast(myHandler);</tt></p>
 *
 * <p><b>Note that this handler has a Pipeline Coverage of "one" which means a new handler must be created
 * for each new channel as the counter cannot be shared among all channels.</b>.</p>
 *
 * <p>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).</p>
 *
 * <p>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.</p>
 *
 * <p>maxTimeToWait, by default set to 15s, allows to specify an upper bound of time shaping.</p>
 * </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(new GenericFutureListener())} on the future returned by
 * {@code ctx.write()}.</li>
 * <li><p>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.</p></li>
 * <li><p>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.</p>
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