/**
* 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.raid;
import java.io.OutputStream;
import java.io.IOException;
import java.util.ArrayList;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.ChecksumException;
import org.apache.hadoop.fs.FileStatus;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.FSDataInputStream;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.hdfs.BlockMissingException;
public class ReedSolomonDecoder extends Decoder {
public static final Log LOG = LogFactory.getLog(
"org.apache.hadoop.raid.ReedSolomonDecoder");
private ErasureCode reedSolomonCode;
public ReedSolomonDecoder(
Configuration conf, int stripeSize, int paritySize) {
super(conf, stripeSize, paritySize);
this.reedSolomonCode = new ReedSolomonCode(stripeSize, paritySize);
}
@Override
protected void fixErasedBlock(
FileSystem fs, Path srcFile,
FileSystem parityFs, Path parityFile,
long blockSize, long errorOffset, long bytesToSkip, long limit,
OutputStream out) throws IOException {
FSDataInputStream[] inputs = new FSDataInputStream[stripeSize + paritySize];
int[] erasedLocations = buildInputs(fs, srcFile, parityFs, parityFile,
errorOffset, inputs);
int blockIdxInStripe = ((int)(errorOffset/blockSize)) % stripeSize;
int erasedLocationToFix = paritySize + blockIdxInStripe;
writeFixedBlock(inputs, erasedLocations, erasedLocationToFix,
bytesToSkip, limit, out);
}
protected int[] buildInputs(FileSystem fs, Path srcFile,
FileSystem parityFs, Path parityFile,
long errorOffset, FSDataInputStream[] inputs)
throws IOException {
LOG.info("Building inputs to recover block starting at " + errorOffset);
FileStatus srcStat = fs.getFileStatus(srcFile);
long blockSize = srcStat.getBlockSize();
long blockIdx = (int)(errorOffset / blockSize);
long stripeIdx = blockIdx / stripeSize;
LOG.info("FileSize = " + srcStat.getLen() + ", blockSize = " + blockSize +
", blockIdx = " + blockIdx + ", stripeIdx = " + stripeIdx);
ArrayList<Integer> erasedLocations = new ArrayList<Integer>();
// First open streams to the parity blocks.
for (int i = 0; i < paritySize; i++) {
long offset = blockSize * (stripeIdx * paritySize + i);
FSDataInputStream in = parityFs.open(
parityFile, conf.getInt("io.file.buffer.size", 64 * 1024));
in.seek(offset);
LOG.info("Adding " + parityFile + ":" + offset + " as input " + i);
inputs[i] = in;
}
// Now open streams to the data blocks.
for (int i = paritySize; i < paritySize + stripeSize; i++) {
long offset = blockSize * (stripeIdx * stripeSize + i - paritySize);
if (offset == errorOffset) {
LOG.info(srcFile + ":" + offset +
" is known to have error, adding zeros as input " + i);
inputs[i] = new FSDataInputStream(new RaidUtils.ZeroInputStream(
offset + blockSize));
erasedLocations.add(i);
} else if (offset > srcStat.getLen()) {
LOG.info(srcFile + ":" + offset +
" is past file size, adding zeros as input " + i);
inputs[i] = new FSDataInputStream(new RaidUtils.ZeroInputStream(
offset + blockSize));
} else {
FSDataInputStream in = fs.open(
srcFile, conf.getInt("io.file.buffer.size", 64 * 1024));
in.seek(offset);
LOG.info("Adding " + srcFile + ":" + offset + " as input " + i);
inputs[i] = in;
}
}
if (erasedLocations.size() > paritySize) {
String msg = "Too many erased locations: " + erasedLocations.size();
LOG.error(msg);
throw new IOException(msg);
}
int[] locs = new int[erasedLocations.size()];
for (int i = 0; i < locs.length; i++) {
locs[i] = erasedLocations.get(i);
}
return locs;
}
/**
* Decode the inputs provided and write to the output.
* @param inputs array of inputs.
* @param erasedLocations indexes in the inputs which are known to be erased.
* @param erasedLocationToFix index in the inputs which needs to be fixed.
* @param skipBytes number of bytes to skip before writing to output.
* @param limit maximum number of bytes to be written/skipped.
* @param out the output.
* @throws IOException
*/
void writeFixedBlock(
FSDataInputStream[] inputs,
int[] erasedLocations,
int erasedLocationToFix,
long skipBytes,
long limit,
OutputStream out) throws IOException {
LOG.info("Need to write " + (limit - skipBytes) +
" bytes for erased location index " + erasedLocationToFix);
int[] tmp = new int[inputs.length];
int[] decoded = new int[erasedLocations.length];
long toDiscard = skipBytes;
// Loop while the number of skipped + written bytes is less than the max.
for (long written = 0; skipBytes + written < limit; ) {
erasedLocations = readFromInputs(inputs, erasedLocations, limit);
if (decoded.length != erasedLocations.length) {
decoded = new int[erasedLocations.length];
}
int toWrite = (int)Math.min((long)bufSize, limit - (skipBytes + written));
if (toDiscard >= toWrite) {
toDiscard -= toWrite;
continue;
}
// Decoded bufSize amount of data.
for (int i = 0; i < bufSize; i++) {
performDecode(readBufs, writeBufs, i, tmp, erasedLocations, decoded);
}
for (int i = 0; i < erasedLocations.length; i++) {
if (erasedLocations[i] == erasedLocationToFix) {
toWrite -= toDiscard;
out.write(writeBufs[i], (int)toDiscard, toWrite);
toDiscard = 0;
written += toWrite;
LOG.debug("Wrote " + toWrite + " bytes for erased location index " +
erasedLocationToFix);
break;
}
}
}
}
int[] readFromInputs(
FSDataInputStream[] inputs,
int[] erasedLocations,
long limit) throws IOException {
// For every input, read some data = bufSize.
for (int i = 0; i < inputs.length; i++) {
long curPos = inputs[i].getPos();
try {
RaidUtils.readTillEnd(inputs[i], readBufs[i], true);
continue;
} catch (BlockMissingException e) {
LOG.error("Encountered BlockMissingException in stream " + i);
} catch (ChecksumException e) {
LOG.error("Encountered ChecksumException in stream " + i);
}
// Found a new erased location.
if (erasedLocations.length == paritySize) {
String msg = "Too many read errors";
LOG.error(msg);
throw new IOException(msg);
}
// Add this stream to the set of erased locations.
int[] newErasedLocations = new int[erasedLocations.length + 1];
for (int j = 0; j < erasedLocations.length; j++) {
newErasedLocations[j] = erasedLocations[j];
}
newErasedLocations[newErasedLocations.length - 1] = i;
erasedLocations = newErasedLocations;
LOG.info("Using zeros for stream " + i);
inputs[i] = new FSDataInputStream(
new RaidUtils.ZeroInputStream(curPos + limit));
inputs[i].seek(curPos);
RaidUtils.readTillEnd(inputs[i], readBufs[i], true);
}
return erasedLocations;
}
void performDecode(byte[][] readBufs, byte[][] writeBufs,
int idx, int[] inputs,
int[] erasedLocations, int[] decoded) {
for (int i = 0; i < decoded.length; i++) {
decoded[i] = 0;
}
for (int i = 0; i < inputs.length; i++) {
inputs[i] = readBufs[i][idx] & 0x000000FF;
}
reedSolomonCode.decode(inputs, erasedLocations, decoded);
for (int i = 0; i < decoded.length; i++) {
writeBufs[i][idx] = (byte)decoded[i];
}
}
}