org.apache.hadoop.hdfs.client.HdfsDataOutputStream.java Source code

Introduction

Here is the source code for org.apache.hadoop.hdfs.client.HdfsDataOutputStream.java

Source

/**
 * 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.client;

import java.io.IOException;
import java.io.OutputStream;
import java.util.EnumSet;

import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.crypto.CryptoOutputStream;
import org.apache.hadoop.fs.FSDataOutputStream;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.hdfs.DFSOutputStream;

import com.google.common.base.Preconditions;

/**
 * The Hdfs implementation of {@link FSDataOutputStream}.
 */
@InterfaceAudience.Public
@InterfaceStability.Evolving
public class HdfsDataOutputStream extends FSDataOutputStream {
    public HdfsDataOutputStream(DFSOutputStream out, FileSystem.Statistics stats, long startPosition)
            throws IOException {
        super(out, stats, startPosition);
    }

    public HdfsDataOutputStream(DFSOutputStream out, FileSystem.Statistics stats) throws IOException {
        this(out, stats, 0L);
    }

    public HdfsDataOutputStream(CryptoOutputStream out, FileSystem.Statistics stats, long startPosition)
            throws IOException {
        super(out, stats, startPosition);
        Preconditions.checkArgument(out.getWrappedStream() instanceof DFSOutputStream,
                "CryptoOutputStream should wrap a DFSOutputStream");
    }

    public HdfsDataOutputStream(CryptoOutputStream out, FileSystem.Statistics stats) throws IOException {
        this(out, stats, 0L);
    }

    /**
     * Get the actual number of replicas of the current block.
     *
     * This can be different from the designated replication factor of the file
     * because the namenode does not maintain replication for the blocks which are
     * currently being written to. Depending on the configuration, the client may
     * continue to write to a block even if a few datanodes in the write pipeline
     * have failed, or the client may add a new datanodes once a datanode has
     * failed.
     *
     * @return the number of valid replicas of the current block
     */
    public synchronized int getCurrentBlockReplication() throws IOException {
        OutputStream wrappedStream = getWrappedStream();
        if (wrappedStream instanceof CryptoOutputStream) {
            wrappedStream = ((CryptoOutputStream) wrappedStream).getWrappedStream();
        }
        return ((DFSOutputStream) wrappedStream).getCurrentBlockReplication();
    }

    /**
     * Sync buffered data to DataNodes (flush to disk devices).
     *
     * @param syncFlags
     *          Indicate the detailed semantic and actions of the hsync.
     * @throws IOException
     * @see FSDataOutputStream#hsync()
     */
    public void hsync(EnumSet<SyncFlag> syncFlags) throws IOException {
        OutputStream wrappedStream = getWrappedStream();
        if (wrappedStream instanceof CryptoOutputStream) {
            wrappedStream.flush();
            wrappedStream = ((CryptoOutputStream) wrappedStream).getWrappedStream();
        }
        ((DFSOutputStream) wrappedStream).hsync(syncFlags);
    }

    public enum SyncFlag {

        /**
         * When doing sync to DataNodes, also update the metadata (block length) in
         * the NameNode.
         */
        UPDATE_LENGTH,

        /**
         * Sync the data to DataNode, close the current block, and allocate a new
         * block
         */
        END_BLOCK
    }
}