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.client;
019
020import java.io.IOException;
021import java.util.EnumSet;
022
023import org.apache.hadoop.classification.InterfaceAudience;
024import org.apache.hadoop.classification.InterfaceStability;
025import org.apache.hadoop.fs.FSDataOutputStream;
026import org.apache.hadoop.fs.FileSystem;
027import org.apache.hadoop.hdfs.DFSOutputStream;
028
029/**
030 * The Hdfs implementation of {@link FSDataOutputStream}.
031 */
032@InterfaceAudience.Public
033@InterfaceStability.Evolving
034public class HdfsDataOutputStream extends FSDataOutputStream {
035  public HdfsDataOutputStream(DFSOutputStream out, FileSystem.Statistics stats,
036      long startPosition) throws IOException {
037    super(out, stats, startPosition);
038  }
039
040  public HdfsDataOutputStream(DFSOutputStream out, FileSystem.Statistics stats
041      ) throws IOException {
042    this(out, stats, 0L);
043  }
044
045  /**
046   * Get the actual number of replicas of the current block.
047   * 
048   * This can be different from the designated replication factor of the file
049   * because the namenode does not maintain replication for the blocks which are
050   * currently being written to. Depending on the configuration, the client may
051   * continue to write to a block even if a few datanodes in the write pipeline
052   * have failed, or the client may add a new datanodes once a datanode has
053   * failed.
054   * 
055   * @return the number of valid replicas of the current block
056   */
057  public synchronized int getCurrentBlockReplication() throws IOException {
058    return ((DFSOutputStream)getWrappedStream()).getCurrentBlockReplication();
059  }
060  
061  /**
062   * Sync buffered data to DataNodes (flush to disk devices).
063   * 
064   * @param syncFlags
065   *          Indicate the detailed semantic and actions of the hsync.
066   * @throws IOException
067   * @see FSDataOutputStream#hsync()
068   */
069  public void hsync(EnumSet<SyncFlag> syncFlags) throws IOException {
070    ((DFSOutputStream) getWrappedStream()).hsync(syncFlags);
071  }
072  
073  public static enum SyncFlag {
074    /**
075     * When doing sync to DataNodes, also update the metadata (block
076     * length) in the NameNode
077     */
078    UPDATE_LENGTH;
079  }
080}