[jira] [Created] (HDFS-4526) If persistBlocks enabled in Namenode, hflush call can avoid persisting blocks with fsync

["Uma Maheswara Rao G (JIRA)" <ji...@apache.org>]

Uma Maheswara Rao G created HDFS-4526:
-----------------------------------------

             Summary: If persistBlocks enabled in Namenode, hflush call can avoid persisting blocks with fsync
                 Key: HDFS-4526
                 URL: https://issues.apache.org/jira/browse/HDFS-4526
             Project: Hadoop HDFS
          Issue Type: Bug
          Components: namenode
    Affects Versions: 2.0.3-alpha, 3.0.0
            Reporter: Uma Maheswara Rao G
            Assignee: Uma Maheswara Rao G


If persists blocks enabled/in HA, evenry getAdditionalBlock will persist the blocks.
So, if user calls Hflush, then client can simply ensure data flushed to DNs and need not worry about fsync. 
Since we can not depend upon client side configuration about persistBlocks, we can just make a fsync call to NN and check whether persistBlocks enabled. If it is enabled, then simply return as it would have already persisted. So, that below peice of code execution can be avoided for every blocks and hflush calls

from fsync:
{code}
 writeLock();
    try {
      checkOperation(OperationCategory.WRITE);
      if (isInSafeMode()) {
        throw new SafeModeException("Cannot fsync file " + src, safeMode);
      }
      INodeFileUnderConstruction pendingFile  = checkLease(src, clientName);
      dir.persistBlocks(src, pendingFile);
    } finally {
      writeUnlock();
    }
    getEditLog().logSync();
{code}

--
This message is automatically generated by JIRA.
If you think it was sent incorrectly, please contact your JIRA administrators
For more information on JIRA, see: http://www.atlassian.com/software/jira