content: /*
   * The Alluxio Open Foundation licenses this work under the Apache License, version 2.0
   * (the "License"). You may not use this work except in compliance with the License, which is
   * available at www.apache.org/licenses/LICENSE-2.0
   *
   * This software is distributed on an "AS IS" basis, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
   * either express or implied, as more fully set forth in the License.
   *
   * See the NOTICE file distributed with this work for information regarding copyright ownership.
   */
  
  package alluxio.worker.block;
  
  import alluxio.client.block.stream.BlockInStream;
  import alluxio.client.file.FileSystemContext;
  import alluxio.metrics.MetricKey;
  import alluxio.metrics.MetricsSystem;
  import alluxio.proto.dataserver.Protocol;
  import alluxio.wire.WorkerNetAddress;
  import alluxio.worker.block.io.BlockReader;
  
  import com.codahale.metrics.Counter;
  import com.google.common.base.Preconditions;
  import io.netty.buffer.ByteBuf;
  
  import java.io.IOException;
  import java.net.InetSocketAddress;
  import java.nio.ByteBuffer;
  import java.nio.channels.Channels;
  import java.nio.channels.ReadableByteChannel;
  
  /**
   * Reads a block from a remote worker node. This should only be used for reading entire blocks.
   */
  public class RemoteBlockReader extends BlockReader {
    private static final Counter BLOCKS_READ_REMOTE =
        MetricsSystem.counter(MetricKey.WORKER_BLOCKS_READ_REMOTE.getName());
  
    private final long mBlockId;
    private final long mBlockSize;
    private final InetSocketAddress mDataSource;
    private final Protocol.OpenUfsBlockOptions mUfsOptions;
    private final FileSystemContext mFsContext;
  
    private BlockInStream mInputStream;
    private ReadableByteChannel mChannel;
    private boolean mClosed;
  
    /**
     * Constructs a remote block reader. It will read from a remote worker based on the data source.
     *
     * @param fsContext the filesystem context to use to create {@link BlockInStream}
     * @param blockId the block to cache
     * @param blockSize the size of the block
     * @param dataSource the data source to cache from
     * @param ufsOptions the options to read the block from ufs if necessary
     */
    public RemoteBlockReader(FileSystemContext fsContext, long blockId, long blockSize,
        InetSocketAddress dataSource,
        Protocol.OpenUfsBlockOptions ufsOptions) {
      mBlockId = blockId;
      mBlockSize = blockSize;
      mDataSource = dataSource;
      mUfsOptions = ufsOptions;
      mClosed = false;
      mFsContext = fsContext;
    }
  
    @Override
    public ByteBuffer read(long offset, long length) throws IOException {
      throw new UnsupportedOperationException("RemoteBlockReader#read is not supported");
    }
  
    @Override
    public long getLength() {
      return mUfsOptions.getBlockSize();
    }
  
    @Override
    public ReadableByteChannel getChannel() {
      Preconditions.checkState(!mClosed);
      init();
      return mChannel;
    }
  
    @Override
    public int transferTo(ByteBuf buf) throws IOException {
      Preconditions.checkState(!mClosed);
      init();
      if (mInputStream == null || mInputStream.remaining() <= 0) {
        return -1;
      }
      int bytesToRead = (int) Math.min(buf.writableBytes(), mInputStream.remaining());
      return buf.writeBytes(mInputStream, bytesToRead);
    }
  
    @Override
    public boolean isClosed() {
      return mClosed;
    }
  
    @Override
    public void close() throws IOException {
      if (mClosed) {
        return;
      }
      super.close();
      if (mInputStream != null) {
        mInputStream.close();
        mChannel.close();
      }
      mClosed = true;
      BLOCKS_READ_REMOTE.inc();
    }
  
    @Override
    public String getLocation() {
      return mDataSource.toString();
    }
  
    private void init() {
      if (mInputStream != null) {
        return;
      }
      WorkerNetAddress address = new WorkerNetAddress().setHost(mDataSource.getHostName())
          .setDataPort(mDataSource.getPort());
      mInputStream = BlockInStream.createRemoteBlockInStream(mFsContext,
          mBlockId,
          address, BlockInStream.BlockInStreamSource.REMOTE, mBlockSize, mUfsOptions);
      mChannel = Channels.newChannel(mInputStream);
    }
  }
  