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From "Raghu Angadi (JIRA)" <j...@apache.org>
Subject [jira] Created: (HADOOP-1471) seekToNewSource() might not work correctly with Checksum failures.
Date Wed, 06 Jun 2007 21:03:25 GMT
seekToNewSource() might not work correctly with Checksum failures.
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                 Key: HADOOP-1471
                 URL: https://issues.apache.org/jira/browse/HADOOP-1471
             Project: Hadoop
          Issue Type: Bug
            Reporter: Raghu Angadi



Patch submitted to HADOOP-893  (by me :( ) seemhave a bug in how it deals with the set {{deadNodes}}.
After the patch, the {{seekToNewSource()}} looks like this :

{code}
    public synchronized boolean seekToNewSource(long targetPos) throws IOException {
      boolean markedDead = deadNodes.contains(currentNode);
      deadNodes.add(currentNode);
      DatanodeInfo oldNode = currentNode;
      DatanodeInfo newNode = blockSeekTo(targetPos);
      if (!markedDead) {
        /* remove it from deadNodes. blockSeekTo could have cleared 
         * deadNodes and added currentNode again. Thats ok. */
        deadNodes.remove(oldNode);
      }
      // ...
{code}

I guess with the expectation that caller of this function decides before the call whether
to put the node in {{deadNodes}} or not. I am not sure whether this was a bug then or not
but it certainly seems to be bug now. i.e. when there is a checksum error with replica1, we
try replica2 and if there a checksum error again, then we try replica1 again! 

Note that ChecksumFileSystem.java was created after HADOOP-893 was resolved.



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