hadoop StripedBlockChecksumReconstructor 源码

haddop StripedBlockChecksumReconstructor 代码

文件路径：/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/erasurecode/StripedBlockChecksumReconstructor.java

/**
 * 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.datanode.erasurecode;

import java.io.Closeable;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.util.Arrays;

import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.hdfs.server.datanode.DataNodeFaultInjector;
import org.apache.hadoop.io.DataOutputBuffer;

/**
 * StripedBlockChecksumReconstructor reconstruct one or more missed striped
 * block in the striped block group, the minimum number of live striped blocks
 * should be no less than data block number. Then checksum will be recalculated
 * using the newly reconstructed block.
 */
@InterfaceAudience.Private
public abstract class StripedBlockChecksumReconstructor
    extends StripedReconstructor implements Closeable {
  private ByteBuffer targetBuffer;
  private final byte[] targetIndices;

  private byte[] checksumBuf;
  private DataOutputBuffer checksumWriter;
  private long checksumDataLen;
  private long requestedLen;

  protected StripedBlockChecksumReconstructor(ErasureCodingWorker worker,
      StripedReconstructionInfo stripedReconInfo,
      DataOutputBuffer checksumWriter,
      long requestedBlockLength) throws IOException {
    super(worker, stripedReconInfo);
    this.targetIndices = stripedReconInfo.getTargetIndices();
    assert targetIndices != null;
    this.checksumWriter = checksumWriter;
    this.requestedLen = requestedBlockLength;
    init();
  }

  private void init() throws IOException {
    initDecoderIfNecessary();
    initDecodingValidatorIfNecessary();
    getStripedReader().init();
    // allocate buffer to keep the reconstructed block data
    targetBuffer = allocateBuffer(getBufferSize());
    long maxTargetLen = 0L;
    for (int targetIndex : targetIndices) {
      maxTargetLen = Math.max(maxTargetLen, getBlockLen(targetIndex));
    }
    setMaxTargetLength(maxTargetLen);
    int checksumSize = getChecksum().getChecksumSize();
    int bytesPerChecksum = getChecksum().getBytesPerChecksum();
    int tmpLen = checksumSize * (getBufferSize() / bytesPerChecksum);
    checksumBuf = new byte[tmpLen];
  }

  @Override
  public void reconstruct() throws IOException {
    prepareDigester();
    long maxTargetLength = getMaxTargetLength();
    while (requestedLen > 0 && getPositionInBlock() < maxTargetLength) {
      DataNodeFaultInjector.get().stripedBlockChecksumReconstruction();
      long remaining = maxTargetLength - getPositionInBlock();
      final int toReconstructLen = (int) Math
          .min(getStripedReader().getBufferSize(), remaining);
      // step1: read from minimum source DNs required for reconstruction.
      // The returned success list is the source DNs we do real read from
      getStripedReader().readMinimumSources(toReconstructLen);

      // step2: decode to reconstruct targets
      reconstructTargets(toReconstructLen);

      // step3: calculate checksum
      checksumDataLen += checksumWithTargetOutput(
          getBufferArray(targetBuffer), toReconstructLen);

      updatePositionInBlock(toReconstructLen);
      requestedLen -= toReconstructLen;
      clearBuffers();
    }

    commitDigest();
  }

  /**
   * Should return a representation of a completed/reconstructed digest which
   * is suitable for debug printing.
   */
  public abstract Object getDigestObject();

  /**
   * This will be called before starting reconstruction.
   */
  abstract void prepareDigester() throws IOException;

  /**
   * This will be called repeatedly with chunked checksums computed in-flight
   * over reconstructed data.
   *
   * @param dataBytesPerChecksum the number of underlying data bytes
   *     corresponding to each checksum inside {@code checksumBytes}.
   */
  abstract void updateDigester(byte[] checksumBytes, int dataBytesPerChecksum)
      throws IOException;

  /**
   * This will be called when reconstruction of entire requested length is
   * complete and any final digests should be committed to
   * implementation-specific output fields.
   */
  abstract void commitDigest() throws IOException;

  protected DataOutputBuffer getChecksumWriter() {
    return checksumWriter;
  }

  private long checksumWithTargetOutput(byte[] outputData, int toReconstructLen)
      throws IOException {
    long checksumDataLength = 0;
    // Calculate partial block checksum. There are two cases.
    // case-1) length of data bytes which is fraction of bytesPerCRC
    // case-2) length of data bytes which is less than bytesPerCRC
    if (requestedLen <= toReconstructLen) {
      int remainingLen = Math.toIntExact(requestedLen);
      outputData = Arrays.copyOf(outputData, remainingLen);

      int partialLength = remainingLen % getChecksum().getBytesPerChecksum();

      int checksumRemaining = (remainingLen
          / getChecksum().getBytesPerChecksum())
          * getChecksum().getChecksumSize();

      int dataOffset = 0;

      // case-1) length of data bytes which is fraction of bytesPerCRC
      if (checksumRemaining > 0) {
        remainingLen = remainingLen - partialLength;
        checksumBuf = new byte[checksumRemaining];
        getChecksum().calculateChunkedSums(outputData, dataOffset,
            remainingLen, checksumBuf, 0);
        updateDigester(checksumBuf, getChecksum().getBytesPerChecksum());
        checksumDataLength = checksumBuf.length;
        dataOffset = remainingLen;
      }

      // case-2) length of data bytes which is less than bytesPerCRC
      if (partialLength > 0) {
        byte[] partialCrc = new byte[getChecksum().getChecksumSize()];
        getChecksum().reset();
        getChecksum().update(outputData, dataOffset, partialLength);
        getChecksum().writeValue(partialCrc, 0, true);
        updateDigester(partialCrc, partialLength);
        checksumDataLength += partialCrc.length;
      }

      clearBuffers();
      // calculated checksum for the requested length, return checksum length.
      return checksumDataLength;
    }
    getChecksum().calculateChunkedSums(outputData, 0,
        outputData.length, checksumBuf, 0);

    // updates digest using the checksum array of bytes
    updateDigester(checksumBuf, getChecksum().getBytesPerChecksum());
    return checksumBuf.length;
  }

  private void reconstructTargets(int toReconstructLen) throws IOException {
    ByteBuffer[] inputs = getStripedReader().getInputBuffers(toReconstructLen);

    ByteBuffer[] outputs = new ByteBuffer[1];
    targetBuffer.limit(toReconstructLen);
    outputs[0] = targetBuffer;
    int[] tarIndices = new int[targetIndices.length];
    for (int i = 0; i < targetIndices.length; i++) {
      tarIndices[i] = targetIndices[i];
    }

    if (isValidationEnabled()) {
      markBuffers(inputs);
      getDecoder().decode(inputs, tarIndices, outputs);
      resetBuffers(inputs);

      getValidator().validate(inputs, tarIndices, outputs);
    } else {
      getDecoder().decode(inputs, tarIndices, outputs);
    }
  }

  /**
   * Clear all associated buffers.
   */
  private void clearBuffers() {
    getStripedReader().clearBuffers();
    targetBuffer.clear();
  }

  public long getChecksumDataLen() {
    return checksumDataLen;
  }

  /**
   * Gets an array corresponding the buffer.
   * @param buffer the input buffer.
   * @return the array with content of the buffer.
   */
  private static byte[] getBufferArray(ByteBuffer buffer) {
    byte[] buff = new byte[buffer.remaining()];
    if (buffer.hasArray()) {
      buff = buffer.array();
    } else {
      buffer.slice().get(buff);
    }
    return buff;
  }

  @Override
  public void close() throws IOException {
    getStripedReader().close();
    cleanup();
  }
}

相关信息

hadoop 源码目录

相关文章

hadoop ErasureCodingWorker 源码

hadoop StripedBlockChecksumCompositeCrcReconstructor 源码

hadoop StripedBlockChecksumMd5CrcReconstructor 源码

hadoop StripedBlockReader 源码

hadoop StripedBlockReconstructor 源码

hadoop StripedBlockWriter 源码

hadoop StripedReader 源码

hadoop StripedReconstructionInfo 源码

hadoop StripedReconstructor 源码

hadoop StripedWriter 源码