Package org.apache.hadoop.fs.impl.prefetch

Class BlockManager

java.lang.Object
org.apache.hadoop.fs.impl.prefetch.BlockManager
All Implemented Interfaces:
Closeable, AutoCloseable
Direct Known Subclasses:
CachingBlockManager
public abstract class BlockManager extends Object implements Closeable
Provides read access to the underlying file one block at a time. This class is the simplest form of a BlockManager that does perform prefetching or caching.

  • Constructor Details

    • BlockManager

      public BlockManager(BlockData blockData)
      Constructs an instance of BlockManager.
      Parameters:
      blockData - information about each block of the underlying file.
      Throws:
      IllegalArgumentException - if blockData is null.

  • Method Details

    • getBlockData

      public BlockData getBlockData()
      Gets block data information.
      Returns:
      instance of BlockData.

    • get

      public BufferData get(int blockNumber) throws IOException
      Gets the block having the given blockNumber. The entire block is read into memory and returned as a BufferData. The blocks are treated as a limited resource and must be released when one is done reading them.
      Parameters:
      blockNumber - the number of the block to be read and returned.
      Returns:
      BufferData having data from the given block.
      Throws:
      IOException - if there an error reading the given block.
      IllegalArgumentException - if blockNumber is negative.

    • read

      public abstract int read(ByteBuffer buffer, long startOffset, int size) throws IOException
      Reads into the given buffer size bytes from the underlying file starting at startOffset.
      Parameters:
      buffer - the buffer to read data in to.
      startOffset - the offset at which reading starts.
      size - the number bytes to read.
      Returns:
      number of bytes read.
      Throws:
      IOException - if there an error reading the given block.

    • release

      public void release(BufferData data)
      Releases resources allocated to the given block.
      Parameters:
      data - the BufferData to release.
      Throws:
      IllegalArgumentException - if data is null.

    • requestPrefetch

      public void requestPrefetch(int blockNumber)
      Requests optional prefetching of the given block.
      Parameters:
      blockNumber - the id of the block to prefetch.
      Throws:
      IllegalArgumentException - if blockNumber is negative.

    • cancelPrefetches

      public void cancelPrefetches()
      Requests cancellation of any previously issued prefetch requests.

    • requestCaching

      public void requestCaching(BufferData data)
      Requests that the given block should be copied to the cache. Optional operation.
      Parameters:
      data - the BufferData instance to optionally cache.

    • close

      public void close()
      Specified by:
      close in interface AutoCloseable
      Specified by:
      close in interface Closeable