hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/StripedDataStreamer.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;

import static org.apache.hadoop.hdfs.protocol.HdfsConstants.BLOCK_STRIPED_CELL_SIZE;
import static org.apache.hadoop.hdfs.protocol.HdfsConstants.NUM_DATA_BLOCKS;
import static org.apache.hadoop.hdfs.protocol.HdfsConstants.NUM_PARITY_BLOCKS;

import java.io.IOException;
import java.util.concurrent.atomic.AtomicReference;

import org.apache.hadoop.hdfs.DFSStripedOutputStream.Coordinator;
import org.apache.hadoop.hdfs.DFSStripedOutputStream.MultipleBlockingQueue;
import org.apache.hadoop.hdfs.protocol.DatanodeInfo;
import org.apache.hadoop.hdfs.protocol.ExtendedBlock;
import org.apache.hadoop.hdfs.protocol.HdfsConstants;
import org.apache.hadoop.hdfs.protocol.HdfsFileStatus;
import org.apache.hadoop.hdfs.protocol.LocatedBlock;
import org.apache.hadoop.hdfs.protocol.LocatedStripedBlock;
import org.apache.hadoop.hdfs.server.datanode.CachingStrategy;
import org.apache.hadoop.hdfs.util.ByteArrayManager;
import org.apache.hadoop.hdfs.util.StripedBlockUtil;
import org.apache.hadoop.util.DataChecksum;
import org.apache.hadoop.util.Progressable;

/**
 * This class extends {@link DataStreamer} to support writing striped blocks
 * to datanodes.
 * A {@link DFSStripedOutputStream} has multiple {@link StripedDataStreamer}s.
 * Whenever the streamers need to talk the namenode, only the fastest streamer
 * sends an rpc call to the namenode and then populates the result for the
 * other streamers.
 */
public class StripedDataStreamer extends DataStreamer {
  /**
   * This class is designed for multiple threads to share a
   * {@link MultipleBlockingQueue}. Initially, the queue is empty. The earliest
   * thread calling poll populates entries to the queue and the other threads
   * will wait for it. Once the entries are populated, all the threads can poll
   * their entries.
   *
   * @param <T> the queue entry type.
   */
  static abstract class ConcurrentPoll<T> {
    private final MultipleBlockingQueue<T> queue;

    ConcurrentPoll(MultipleBlockingQueue<T> queue) {
      this.queue = queue;
    }

    T poll(final int i) throws IOException {
      for(;;) {
        synchronized(queue) {
          final T polled = queue.poll(i);
          if (polled != null) { // already populated; return polled item.
            return polled;
          }
          if (isReady2Populate()) {
            populate();
            return queue.poll(i);
          }
        }

        // sleep and then retry.
        try {
          Thread.sleep(100);
        } catch(InterruptedException ie) {
          throw DFSUtil.toInterruptedIOException(
              "Sleep interrupted during poll", ie);
        }
      }
    }

    boolean isReady2Populate() {
      return queue.isEmpty();
    }

    abstract void populate() throws IOException;
  }

  private final Coordinator coordinator;
  private final int index;
  private volatile boolean failed;

  StripedDataStreamer(HdfsFileStatus stat,
                      DFSClient dfsClient, String src,
                      Progressable progress, DataChecksum checksum,
                      AtomicReference<CachingStrategy> cachingStrategy,
                      ByteArrayManager byteArrayManage, String[] favoredNodes,
                      short index, Coordinator coordinator) {
    super(stat, null, dfsClient, src, progress, checksum, cachingStrategy,
        byteArrayManage, favoredNodes);
    this.index = index;
    this.coordinator = coordinator;
  }

  int getIndex() {
    return index;
  }

  void setFailed(boolean failed) {
    this.failed = failed;
  }

  boolean isFailed() {
    return failed;
  }

  private boolean isParityStreamer() {
    return index >= NUM_DATA_BLOCKS;
  }

  @Override
  protected void endBlock() {
    if (!isParityStreamer()) {
      coordinator.offerEndBlock(index, block);
    }
    super.endBlock();
  }

  @Override
  protected LocatedBlock locateFollowingBlock(final DatanodeInfo[] excludedNodes)
      throws IOException {
    final MultipleBlockingQueue<LocatedBlock> followingBlocks
        = coordinator.getFollowingBlocks();
    return new ConcurrentPoll<LocatedBlock>(followingBlocks) {
      @Override
      boolean isReady2Populate() {
        return super.isReady2Populate()
            && (block == null || coordinator.hasAllEndBlocks());
      }

      @Override
      void populate() throws IOException {
        getLastException().check(false);

        if (block != null) {
          // set numByte for the previous block group
          long bytes = 0;
          for (int i = 0; i < NUM_DATA_BLOCKS; i++) {
            final ExtendedBlock b = coordinator.takeEndBlock(i);
            StripedBlockUtil.checkBlocks(index, block, i, b);
            bytes += b.getNumBytes();
          }
          block.setNumBytes(bytes);
          block.setBlockId(block.getBlockId() - index);
        }

        if (LOG.isDebugEnabled()) {
          LOG.debug("locateFollowingBlock: index=" + index + ", block=" + block);
        }

        final LocatedBlock lb = StripedDataStreamer.super.locateFollowingBlock(
            excludedNodes);
        if (lb.getLocations().length < HdfsConstants.NUM_DATA_BLOCKS) {
          throw new IOException(
              "Failed to get datablocks number of nodes from namenode: blockGroupSize= "
                  + (HdfsConstants.NUM_DATA_BLOCKS + HdfsConstants.NUM_PARITY_BLOCKS)
                  + ", blocks.length= " + lb.getLocations().length);
        }
        final LocatedBlock[] blocks = StripedBlockUtil.parseStripedBlockGroup(
            (LocatedStripedBlock)lb,
            BLOCK_STRIPED_CELL_SIZE, NUM_DATA_BLOCKS, NUM_PARITY_BLOCKS);

        for (int i = 0; i < blocks.length; i++) {
          StripedDataStreamer si = coordinator.getStripedDataStreamer(i);
          if (si.isFailed()) {
            continue; // skipping failed data streamer
          }
          if (blocks[i] == null) {
            // Set exception and close streamer as there is no block locations
            // found for the parity block.
            LOG.warn("Failed to get block location for parity block, index="
                + i);
            si.getLastException().set(
                new IOException("Failed to get following block, i=" + i));
            si.setFailed(true);
            si.endBlock();
            si.close(true);
          } else {
            followingBlocks.offer(i, blocks[i]);
          }
        }
      }
    }.poll(index);
  }

  @Override
  LocatedBlock updateBlockForPipeline() throws IOException {
    final MultipleBlockingQueue<LocatedBlock> newBlocks
        = coordinator.getNewBlocks();
    return new ConcurrentPoll<LocatedBlock>(newBlocks) {
      @Override
      void populate() throws IOException {
        final ExtendedBlock bg = coordinator.getBlockGroup();
        final LocatedBlock updated = callUpdateBlockForPipeline(bg);
        final long newGS = updated.getBlock().getGenerationStamp();
        final LocatedBlock[] updatedBlks = StripedBlockUtil
            .parseStripedBlockGroup((LocatedStripedBlock) updated,
                BLOCK_STRIPED_CELL_SIZE, NUM_DATA_BLOCKS, NUM_PARITY_BLOCKS);
        for (int i = 0; i < NUM_DATA_BLOCKS + NUM_PARITY_BLOCKS; i++) {
          StripedDataStreamer si = coordinator.getStripedDataStreamer(i);
          if (si.isFailed()) {
            continue; // skipping failed data streamer
          }
          final ExtendedBlock bi = si.getBlock();
          if (bi != null) {
            final LocatedBlock lb = new LocatedBlock(newBlock(bi, newGS),
                null, null, null, -1, updated.isCorrupt(), null);
            lb.setBlockToken(updatedBlks[i].getBlockToken());
            newBlocks.offer(i, lb);
          } else {
            final LocatedBlock lb = coordinator.getFollowingBlocks().peek(i);
            lb.getBlock().setGenerationStamp(newGS);
          }
        }
      }
    }.poll(index);
  }

  @Override
  ExtendedBlock updatePipeline(final long newGS) throws IOException {
    final MultipleBlockingQueue<ExtendedBlock> updateBlocks
        = coordinator.getUpdateBlocks();
    return new ConcurrentPoll<ExtendedBlock>(updateBlocks) {
      @Override
      void populate() throws IOException {
        final ExtendedBlock bg = coordinator.getBlockGroup();
        final ExtendedBlock newBG = newBlock(bg, newGS);
        final ExtendedBlock updated = callUpdatePipeline(bg, newBG);
        for (int i = 0; i < NUM_DATA_BLOCKS + NUM_PARITY_BLOCKS; i++) {
          StripedDataStreamer si = coordinator.getStripedDataStreamer(i);
          if (si.isFailed()) {
            continue; // skipping failed data streamer
          }
          final ExtendedBlock bi = si.getBlock();
          updateBlocks.offer(i, newBlock(bi, updated.getGenerationStamp()));
        }
      }
    }.poll(index);
  }

  @Override
  public String toString() {
    return "#" + index + ": failed? " + Boolean.toString(failed).charAt(0)
        + ", " + super.toString();
  }
}