class DatanodeDescriptor extends DatanodeInfo {

  public Block[] getInvalidateBlocks(int maxblocks) {
    synchronized (invalidateBlocks) {
      Block[] deleteList = invalidateBlocks.pollToArray(new Block[Math.min(
          invalidateBlocks.size(), maxblocks)]);
      return deleteList.length == 0 ? null : deleteList;
    }
  }

  public  DatanodeDescriptor(DatanodeID nodeID);
  public  DatanodeDescriptor(DatanodeID nodeID, 
                            String networkLocation);

}