001/**
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *     http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018package org.apache.hadoop.hdfs.server.balancer;
019
020import java.util.ArrayList;
021import java.util.HashMap;
022import java.util.List;
023import java.util.Map;
024
025import org.apache.hadoop.hdfs.protocol.Block;
026import org.apache.hadoop.util.Time;
027
028/**
029 * This window makes sure to keep blocks that have been moved within a fixed
030 * time interval (default is 1.5 hour). Old window has blocks that are older;
031 * Current window has blocks that are more recent; Cleanup method triggers the
032 * check if blocks in the old window are more than the fixed time interval. If
033 * yes, purge the old window and then move blocks in current window to old
034 * window.
035 * 
036 * @param <L> Location type
037 */
038public class MovedBlocks<L> {
039  /** A class for keeping track of a block and its locations */
040  public static class Locations<L> {
041    private final Block block; // the block
042    /** The locations of the replicas of the block. */
043    protected final List<L> locations = new ArrayList<L>(3);
044    
045    public Locations(Block block) {
046      this.block = block;
047    }
048    
049    /** clean block locations */
050    public synchronized void clearLocations() {
051      locations.clear();
052    }
053    
054    /** add a location */
055    public synchronized void addLocation(L loc) {
056      if (!locations.contains(loc)) {
057        locations.add(loc);
058      }
059    }
060    
061    /** @return if the block is located on the given location. */
062    public synchronized boolean isLocatedOn(L loc) {
063      return locations.contains(loc);
064    }
065    
066    /** @return its locations */
067    public synchronized List<L> getLocations() {
068      return locations;
069    }
070    
071    /* @return the block */
072    public Block getBlock() {
073      return block;
074    }
075    
076    /* Return the length of the block */
077    public long getNumBytes() {
078      return block.getNumBytes();
079    }
080  }
081
082  private static final int CUR_WIN = 0;
083  private static final int OLD_WIN = 1;
084  private static final int NUM_WINS = 2;
085
086  private final long winTimeInterval;
087  private long lastCleanupTime = Time.monotonicNow();
088  private final List<Map<Block, Locations<L>>> movedBlocks
089      = new ArrayList<Map<Block, Locations<L>>>(NUM_WINS);
090  
091  /** initialize the moved blocks collection */
092  public MovedBlocks(long winTimeInterval) {
093    this.winTimeInterval = winTimeInterval;
094    movedBlocks.add(newMap());
095    movedBlocks.add(newMap());
096  }
097
098  private Map<Block, Locations<L>> newMap() {
099    return new HashMap<Block, Locations<L>>();
100  }
101
102  /** add a block thus marking a block to be moved */
103  public synchronized void put(Locations<L> block) {
104    movedBlocks.get(CUR_WIN).put(block.getBlock(), block);
105  }
106
107  /** @return if a block is marked as moved */
108  public synchronized boolean contains(Block block) {
109    return movedBlocks.get(CUR_WIN).containsKey(block) ||
110      movedBlocks.get(OLD_WIN).containsKey(block);
111  }
112
113  /** remove old blocks */
114  public synchronized void cleanup() {
115    long curTime = Time.monotonicNow();
116    // check if old win is older than winWidth
117    if (lastCleanupTime + winTimeInterval <= curTime) {
118      // purge the old window
119      movedBlocks.set(OLD_WIN, movedBlocks.get(CUR_WIN));
120      movedBlocks.set(CUR_WIN, newMap());
121      lastCleanupTime = curTime;
122    }
123  }
124}