| /** |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF 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 org.apache.hadoop.hdfs.util; |
| |
| /** |
| * a class to throttle the data transfers. |
| * This class is thread safe. It can be shared by multiple threads. |
| * The parameter bandwidthPerSec specifies the total bandwidth shared by |
| * threads. |
| */ |
| public class DataTransferThrottler { |
| private long period; // period over which bw is imposed |
| private long periodExtension; // Max period over which bw accumulates. |
| private long bytesPerPeriod; // total number of bytes can be sent in each period |
| private long curPeriodStart; // current period starting time |
| private long curReserve; // remaining bytes can be sent in the period |
| private long bytesAlreadyUsed; |
| |
| /** Constructor |
| * @param bandwidthPerSec bandwidth allowed in bytes per second. |
| */ |
| public DataTransferThrottler(long bandwidthPerSec) { |
| this(500, bandwidthPerSec); // by default throttling period is 500ms |
| } |
| |
| /** |
| * Constructor |
| * @param period in milliseconds. Bandwidth is enforced over this |
| * period. |
| * @param bandwidthPerSec bandwidth allowed in bytes per second. |
| */ |
| public DataTransferThrottler(long period, long bandwidthPerSec) { |
| this.curPeriodStart = System.currentTimeMillis(); |
| this.period = period; |
| this.curReserve = this.bytesPerPeriod = bandwidthPerSec*period/1000; |
| this.periodExtension = period*3; |
| } |
| |
| /** |
| * @return current throttle bandwidth in bytes per second. |
| */ |
| public synchronized long getBandwidth() { |
| return bytesPerPeriod*1000/period; |
| } |
| |
| /** |
| * Sets throttle bandwidth. This takes affect latest by the end of current |
| * period. |
| * |
| * @param bytesPerSecond |
| */ |
| public synchronized void setBandwidth(long bytesPerSecond) { |
| if ( bytesPerSecond <= 0 ) { |
| throw new IllegalArgumentException("" + bytesPerSecond); |
| } |
| bytesPerPeriod = bytesPerSecond*period/1000; |
| } |
| |
| /** Given the numOfBytes sent/received since last time throttle was called, |
| * make the current thread sleep if I/O rate is too fast |
| * compared to the given bandwidth. |
| * |
| * @param numOfBytes |
| * number of bytes sent/received since last time throttle was called |
| */ |
| public synchronized void throttle(long numOfBytes) { |
| if ( numOfBytes <= 0 ) { |
| return; |
| } |
| |
| curReserve -= numOfBytes; |
| bytesAlreadyUsed += numOfBytes; |
| |
| while (curReserve <= 0) { |
| long now = System.currentTimeMillis(); |
| long curPeriodEnd = curPeriodStart + period; |
| |
| if ( now < curPeriodEnd ) { |
| // Wait for next period so that curReserve can be increased. |
| try { |
| wait( curPeriodEnd - now ); |
| } catch (InterruptedException ignored) {} |
| } else if ( now < (curPeriodStart + periodExtension)) { |
| curPeriodStart = curPeriodEnd; |
| curReserve += bytesPerPeriod; |
| } else { |
| // discard the prev period. Throttler might not have |
| // been used for a long time. |
| curPeriodStart = now; |
| curReserve = bytesPerPeriod - bytesAlreadyUsed; |
| } |
| } |
| |
| bytesAlreadyUsed -= numOfBytes; |
| } |
| } |