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From "Li Junjun (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HDFS-3448) CLONE - Why open method in class DFSClient would compare old LocatedBlocks and new LocatedBlocks?
Date Mon, 21 May 2012 03:28:41 GMT
Li Junjun created HDFS-3448:
-------------------------------

             Summary: CLONE - Why open method in class DFSClient would compare old LocatedBlocks
and new LocatedBlocks?
                 Key: HDFS-3448
                 URL: https://issues.apache.org/jira/browse/HDFS-3448
             Project: Hadoop HDFS
          Issue Type: Wish
            Reporter: Li Junjun
            Assignee: Todd Lipcon


This is in the package of org.apache.hadoop.hdfs, DFSClient.openInfo():
if (locatedBlocks != null) {
        Iterator<LocatedBlock> oldIter = locatedBlocks.getLocatedBlocks().iterator();
        Iterator<LocatedBlock> newIter = newInfo.getLocatedBlocks().iterator();
        while (oldIter.hasNext() && newIter.hasNext()) {
          if (! oldIter.next().getBlock().equals(newIter.next().getBlock())) {
            throw new IOException("Blocklist for " + src + " has changed!");
          }
        }
      }
Why we need compare old LocatedBlocks and new LocatedBlocks, and in what case it happen?
Why not "this.locatedBlocks = newInfo" directly?

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