org.apache.hadoop.io.erasurecode.coder.HHXORErasureDecoder Maven / Gradle / Ivy
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* 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.io.erasurecode.coder;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.io.erasurecode.CodecUtil;
import org.apache.hadoop.io.erasurecode.ECBlock;
import org.apache.hadoop.io.erasurecode.ECBlockGroup;
import org.apache.hadoop.io.erasurecode.ErasureCodeConstants;
import org.apache.hadoop.io.erasurecode.ErasureCoderOptions;
import org.apache.hadoop.io.erasurecode.rawcoder.RawErasureDecoder;
import org.apache.hadoop.io.erasurecode.rawcoder.RawErasureEncoder;
/**
* Hitchhiker is a new erasure coding algorithm developed as a research project
* at UC Berkeley by Rashmi Vinayak.
* It has been shown to reduce network traffic and disk I/O by 25%-45% during
* data reconstruction while retaining the same storage capacity and failure
* tolerance capability of RS codes.
* The Hitchhiker algorithm is described in K.V.Rashmi, et al.,
* "A "Hitchhiker's" Guide to Fast and Efficient Data Reconstruction in
* Erasure-coded Data Centers", in ACM SIGCOMM 2014.
* This is Hitchhiker-XOR erasure decoder that decodes a block group.
*/
@InterfaceAudience.Private
public class HHXORErasureDecoder extends ErasureDecoder {
private RawErasureDecoder rsRawDecoder;
private RawErasureEncoder xorRawEncoder;
public HHXORErasureDecoder(ErasureCoderOptions options) {
super(options);
}
@Override
protected ErasureCodingStep prepareDecodingStep(
final ECBlockGroup blockGroup) {
RawErasureDecoder rawDecoder;
RawErasureEncoder rawEncoder;
ECBlock[] inputBlocks = getInputBlocks(blockGroup);
ECBlock[] outputBlocks = getOutputBlocks(blockGroup);
rawDecoder = checkCreateRSRawDecoder();
rawEncoder = checkCreateXorRawEncoder();
return new HHXORErasureDecodingStep(inputBlocks,
getErasedIndexes(inputBlocks), outputBlocks, rawDecoder,
rawEncoder);
}
private RawErasureDecoder checkCreateRSRawDecoder() {
if (rsRawDecoder == null) {
rsRawDecoder = CodecUtil.createRawDecoder(getConf(),
ErasureCodeConstants.RS_CODEC_NAME, getOptions());
}
return rsRawDecoder;
}
private RawErasureEncoder checkCreateXorRawEncoder() {
if (xorRawEncoder == null) {
xorRawEncoder = CodecUtil.createRawEncoder(getConf(),
ErasureCodeConstants.XOR_CODEC_NAME, getOptions());
}
return xorRawEncoder;
}
@Override
public boolean preferDirectBuffer() {
return false;
}
@Override
public void release() {
if (rsRawDecoder != null) {
rsRawDecoder.release();
}
if (xorRawEncoder != null) {
xorRawEncoder.release();
}
}
}