io.hops.erasure_coding.XORDecoder.java Source code

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Here is the source code for io.hops.erasure_coding.XORDecoder.java

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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 io.hops.erasure_coding;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FSDataInputStream;
import org.apache.hadoop.fs.FileStatus;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.util.Progressable;

import java.io.IOException;
import java.io.OutputStream;
import java.util.zip.CRC32;

public class XORDecoder extends Decoder {
    public static final Log LOG = LogFactory.getLog("org.apache.hadoop.raid.XORDecoder");

    private int stripeSize;

    public XORDecoder(Configuration conf) {
        super(conf, Codec.getCodec("xor"));
        stripeSize = this.codec.stripeLength;
    }

    @Override
    protected long fixErasedBlockImpl(FileSystem fs, Path srcFile, FileSystem parityFs, Path parityFile,
            boolean fixSource, long blockSize, long errorOffset, long limit, boolean partial, OutputStream out,
            Progressable reporter, CRC32 crc) throws IOException {
        if (partial) {
            throw new IOException("We don't support partial reconstruction");
        }
        LOG.info("Fixing block at " + srcFile + ":" + errorOffset + ", limit " + limit);
        if (crc != null) {
            crc.reset();
        }
        FileStatus srcStat = fs.getFileStatus(srcFile);
        FSDataInputStream[] inputs = new FSDataInputStream[stripeSize + this.codec.parityLength];

        try {
            long errorBlockOffset = (errorOffset / blockSize) * blockSize;
            long[] srcOffsets = stripeOffsets(errorOffset, blockSize, fixSource);
            for (int i = 0; i < srcOffsets.length; i++) {
                if (fixSource && srcOffsets[i] == errorBlockOffset) {
                    inputs[i] = new FSDataInputStream(new RaidUtils.ZeroInputStream(blockSize));
                    LOG.info("Using zeros at " + srcFile + ":" + errorBlockOffset);
                    continue;
                }
                if (srcOffsets[i] < srcStat.getLen()) {
                    FSDataInputStream in = fs.open(srcFile);
                    in.seek(srcOffsets[i]);
                    inputs[i] = in;
                } else {
                    inputs[i] = new FSDataInputStream(new RaidUtils.ZeroInputStream(blockSize));
                    LOG.info("Using zeros at " + srcFile + ":" + errorBlockOffset);
                }
            }

            if (fixSource) {
                FSDataInputStream parityFileIn = parityFs.open(parityFile);
                parityFileIn.seek(parityOffset(errorOffset, blockSize));
                inputs[inputs.length - 1] = parityFileIn;
            } else {
                inputs[inputs.length - 1] = new FSDataInputStream(new RaidUtils.ZeroInputStream(blockSize));
                LOG.info("Using zeros at " + parityFile + ":" + errorBlockOffset);
            }
        } catch (IOException e) {
            RaidUtils.closeStreams(inputs);
            throw e;
        }

        int boundedBufferCapacity = 1;
        ParallelStreamReader parallelReader = new ParallelStreamReader(reporter, inputs, bufSize, parallelism,
                boundedBufferCapacity, blockSize);
        parallelReader.start();
        try {
            // Loop while the number of skipped + written bytes is less than the max.
            long written;
            for (written = 0; written < limit;) {
                ParallelStreamReader.ReadResult readResult;
                try {
                    readResult = parallelReader.getReadResult();
                } catch (InterruptedException e) {
                    throw new IOException("Interrupted while waiting for read result");
                }
                // Cannot tolerate any IO errors.
                IOException readEx = readResult.getException();
                if (readEx != null) {
                    throw readEx;
                }

                int toWrite = (int) Math.min((long) bufSize, limit - written);

                XOREncoder.xor(readResult.readBufs, writeBufs[0]);

                out.write(writeBufs[0], 0, toWrite);
                if (crc != null) {
                    crc.update(writeBufs[0], 0, toWrite);
                }
                written += toWrite;
            }
            return written;
        } finally {
            // Inputs will be closed by parallelReader.shutdown().
            parallelReader.shutdown();
        }
    }

    protected long[] stripeOffsets(long errorOffset, long blockSize, boolean fixSource) {
        long[] offsets = new long[stripeSize];
        long stripeIdx;
        if (fixSource) {
            stripeIdx = errorOffset / (blockSize * stripeSize);
        } else {
            stripeIdx = errorOffset / blockSize;
        }
        long startOffsetOfStripe = stripeIdx * stripeSize * blockSize;
        for (int i = 0; i < stripeSize; i++) {
            offsets[i] = startOffsetOfStripe + i * blockSize;
        }
        return offsets;
    }

    protected long parityOffset(long errorOffset, long blockSize) {
        long stripeIdx = errorOffset / (blockSize * stripeSize);
        return stripeIdx * blockSize;
    }
}