hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocol/LocatedBlock.java

/**
 * 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.protocol;

import java.util.List;

import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.hdfs.security.token.block.BlockTokenIdentifier;
import org.apache.hadoop.security.token.Token;

import com.google.common.base.Preconditions;
import com.google.common.collect.Lists;

/**
 * Associates a block with the Datanodes that contain its replicas
 * and other block metadata (E.g. the file offset associated with this
 * block, whether it is corrupt, a location is cached in memory,
 * security token, etc).
 */
@InterfaceAudience.Private
@InterfaceStability.Evolving
public class LocatedBlock {

  private ExtendedBlock b;
  private long offset;  // offset of the first byte of the block in the file
  private DatanodeInfo[] locs;
  // corrupt flag is true if all of the replicas of a block are corrupt.
  // else false. If block has few corrupt replicas, they are filtered and 
  // their locations are not part of this object
  private boolean corrupt;
  private Token<BlockTokenIdentifier> blockToken = new Token<BlockTokenIdentifier>();
  /**
   * List of cached datanode locations
   */
  private DatanodeInfo[] cachedLocs;

  // Used when there are no locations
  private static final DatanodeInfo[] EMPTY_LOCS = new DatanodeInfo[0];

  public LocatedBlock(ExtendedBlock b, DatanodeInfo[] locs) {
    this(b, locs, -1); // startOffset is unknown
  }

  public LocatedBlock(ExtendedBlock b, DatanodeInfo[] locs, long startOffset) {
    this(b, locs, startOffset, false);
  }

  public LocatedBlock(ExtendedBlock b, DatanodeInfo[] locs, long startOffset, 
                      boolean corrupt) {
    this(b, locs, startOffset, corrupt, EMPTY_LOCS);
  }

  public LocatedBlock(ExtendedBlock b, DatanodeInfo[] locs, long startOffset,
      boolean corrupt, DatanodeInfo[] cachedLocs) {
    this.b = b;
    this.offset = startOffset;
    this.corrupt = corrupt;
    if (locs==null) {
      this.locs = EMPTY_LOCS;
    } else {
      this.locs = locs;
    }
    Preconditions.checkArgument(cachedLocs != null,
        "cachedLocs should not be null, use a different constructor");
    if (cachedLocs.length == 0) {
      this.cachedLocs = EMPTY_LOCS;
    } else {
      this.cachedLocs = cachedLocs;
    }
  }

  public Token<BlockTokenIdentifier> getBlockToken() {
    return blockToken;
  }

  public void setBlockToken(Token<BlockTokenIdentifier> token) {
    this.blockToken = token;
  }

  public ExtendedBlock getBlock() {
    return b;
  }

  public DatanodeInfo[] getLocations() {
    return locs;
  }
  
  public long getStartOffset() {
    return offset;
  }
  
  public long getBlockSize() {
    return b.getNumBytes();
  }

  void setStartOffset(long value) {
    this.offset = value;
  }

  void setCorrupt(boolean corrupt) {
    this.corrupt = corrupt;
  }
  
  public boolean isCorrupt() {
    return this.corrupt;
  }

  /**
   * Add a the location of a cached replica of the block.
   * 
   * @param loc of datanode with the cached replica
   */
  public void addCachedLoc(DatanodeInfo loc) {
    List<DatanodeInfo> cachedList = Lists.newArrayList(cachedLocs);
    if (cachedList.contains(loc)) {
      return;
    }
    // Try to re-use a DatanodeInfo already in loc
    for (int i=0; i<locs.length; i++) {
      if (locs[i].equals(loc)) {
        cachedList.add(locs[i]);
        cachedLocs = cachedList.toArray(cachedLocs);
        return;
      }
    }
    // Not present in loc, add it and go
    cachedList.add(loc);
    cachedLocs = cachedList.toArray(cachedLocs);
  }

  /**
   * @return Datanodes with a cached block replica
   */
  public DatanodeInfo[] getCachedLocations() {
    return cachedLocs;
  }

  @Override
  public String toString() {
    return getClass().getSimpleName() + "{" + b
        + "; getBlockSize()=" + getBlockSize()
        + "; corrupt=" + corrupt
        + "; offset=" + offset
        + "; locs=" + java.util.Arrays.asList(locs)
        + "}";
  }
}