[HADOOP-4388] Bug in Datanode transferBlocks code

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 0.17.0
• Fix Version/s: 0.20.0
• Hadoop Flags: Reviewed
• Assignee: Suresh Srinivas
• Reporter: Suresh Srinivas
• Created: 10/Oct/08 17:20
• Updated: 08/Jul/09 16:43
• Resolved: 04/Nov/08 18:45

Description

In the following code, when the blocks to be transferred has an invalid block, all the blocks that follow it are also not transferred. That might not be the intended behavior. Instead of breaking out of the loop, perhaps the right thing to do is to ignore the invalid block and continue with transferring the rest.

  private void transferBlocks( Block blocks[], 
                               DatanodeInfo xferTargets[][] 
                               ) throws IOException {
    for (int i = 0; i < blocks.length; i++) {
      if (!data.isValidBlock(blocks[i])) {
        String errStr = "Can't send invalid block " + blocks[i];
        LOG.info(errStr);
        namenode.errorReport(dnRegistration, 
                             DatanodeProtocol.INVALID_BLOCK, 
                             errStr);
        //
        // ******** This should be continue instead of break?
        //
        break;
      }
      int numTargets = xferTargets[i].length;
      if (numTargets > 0) {
        if (LOG.isInfoEnabled()) {
          StringBuilder xfersBuilder = new StringBuilder();
          for (int j = 0; j < numTargets; j++) {
            DatanodeInfo nodeInfo = xferTargets[i][j];
            xfersBuilder.append(nodeInfo.getName());
            if (j < (numTargets - 1)) {
              xfersBuilder.append(", ");
            }
          }
          String xfersTo = xfersBuilder.toString();
          LOG.info(dnRegistration + " Starting thread to transfer block " + 
                   blocks[i] + " to " + xfersTo);                       
        }
        new Daemon(new DataTransfer(xferTargets[i], blocks[i], this)).start();
      }
    }
  }