| /** |
| * 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.server.namenode; |
| |
| import java.io.BufferedInputStream; |
| import java.io.BufferedOutputStream; |
| import java.io.DataInput; |
| import java.io.DataInputStream; |
| import java.io.DataOutputStream; |
| import java.io.IOException; |
| import java.io.InputStream; |
| import java.io.OutputStream; |
| |
| import org.apache.hadoop.classification.InterfaceAudience; |
| import org.apache.hadoop.classification.InterfaceStability; |
| import org.apache.hadoop.conf.Configuration; |
| import org.apache.hadoop.hdfs.DFSConfigKeys; |
| import org.apache.hadoop.io.Text; |
| import org.apache.hadoop.io.compress.CompressionCodec; |
| import org.apache.hadoop.io.compress.CompressionCodecFactory; |
| |
| /** |
| * Simple container class that handles support for compressed fsimage files. |
| */ |
| @InterfaceAudience.Private |
| @InterfaceStability.Evolving |
| public class FSImageCompression { |
| |
| /** Codec to use to save or load image, or null if the image is not compressed */ |
| private CompressionCodec imageCodec; |
| |
| /** |
| * Create a "noop" compression - i.e. uncompressed |
| */ |
| private FSImageCompression() { |
| } |
| |
| /** |
| * Create compression using a particular codec |
| */ |
| private FSImageCompression(CompressionCodec codec) { |
| imageCodec = codec; |
| } |
| |
| public CompressionCodec getImageCodec() { |
| return imageCodec; |
| } |
| |
| /** |
| * Create a "noop" compression - i.e. uncompressed |
| */ |
| static FSImageCompression createNoopCompression() { |
| return new FSImageCompression(); |
| } |
| |
| /** |
| * Create a compression instance based on the user's configuration in the given |
| * Configuration object. |
| * @throws IOException if the specified codec is not available. |
| */ |
| static FSImageCompression createCompression(Configuration conf) |
| throws IOException { |
| boolean compressImage = conf.getBoolean( |
| DFSConfigKeys.DFS_IMAGE_COMPRESS_KEY, |
| DFSConfigKeys.DFS_IMAGE_COMPRESS_DEFAULT); |
| |
| if (!compressImage) { |
| return createNoopCompression(); |
| } |
| |
| String codecClassName = conf.get( |
| DFSConfigKeys.DFS_IMAGE_COMPRESSION_CODEC_KEY, |
| DFSConfigKeys.DFS_IMAGE_COMPRESSION_CODEC_DEFAULT); |
| return createCompression(conf, codecClassName); |
| } |
| |
| /** |
| * Create a compression instance using the codec specified by |
| * <code>codecClassName</code> |
| */ |
| static FSImageCompression createCompression(Configuration conf, |
| String codecClassName) |
| throws IOException { |
| |
| CompressionCodecFactory factory = new CompressionCodecFactory(conf); |
| CompressionCodec codec = factory.getCodecByClassName(codecClassName); |
| if (codec == null) { |
| throw new IOException("Not a supported codec: " + codecClassName); |
| } |
| |
| return new FSImageCompression(codec); |
| } |
| |
| /** |
| * Create a compression instance based on a header read from an input stream. |
| * @throws IOException if the specified codec is not available or the |
| * underlying IO fails. |
| */ |
| static FSImageCompression readCompressionHeader( |
| Configuration conf, DataInput in) throws IOException |
| { |
| boolean isCompressed = in.readBoolean(); |
| |
| if (!isCompressed) { |
| return createNoopCompression(); |
| } else { |
| String codecClassName = Text.readString(in); |
| return createCompression(conf, codecClassName); |
| } |
| } |
| |
| /** |
| * Unwrap a compressed input stream by wrapping it with a decompressor based |
| * on this codec. If this instance represents no compression, simply adds |
| * buffering to the input stream. |
| * @return a buffered stream that provides uncompressed data |
| * @throws IOException If the decompressor cannot be instantiated or an IO |
| * error occurs. |
| */ |
| DataInputStream unwrapInputStream(InputStream is) throws IOException { |
| if (imageCodec != null) { |
| return new DataInputStream(imageCodec.createInputStream(is)); |
| } else { |
| return new DataInputStream(new BufferedInputStream(is)); |
| } |
| } |
| |
| /** |
| * Write out a header to the given stream that indicates the chosen |
| * compression codec, and return the same stream wrapped with that codec. |
| * If no codec is specified, simply adds buffering to the stream, so that |
| * the returned stream is always buffered. |
| * |
| * @param os The stream to write header to and wrap. This stream should |
| * be unbuffered. |
| * @return A stream wrapped with the specified compressor, or buffering |
| * if compression is not enabled. |
| * @throws IOException if an IO error occurs or the compressor cannot be |
| * instantiated |
| */ |
| DataOutputStream writeHeaderAndWrapStream(OutputStream os) |
| throws IOException { |
| DataOutputStream dos = new DataOutputStream(os); |
| |
| dos.writeBoolean(imageCodec != null); |
| |
| if (imageCodec != null) { |
| String codecClassName = imageCodec.getClass().getCanonicalName(); |
| Text.writeString(dos, codecClassName); |
| |
| return new DataOutputStream(imageCodec.createOutputStream(os)); |
| } else { |
| // use a buffered output stream |
| return new DataOutputStream(new BufferedOutputStream(os)); |
| } |
| } |
| |
| @Override |
| public String toString() { |
| if (imageCodec != null) { |
| return "codec " + imageCodec.getClass().getCanonicalName(); |
| } else { |
| return "no compression"; |
| } |
| } |
| } |