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From "Rakesh R (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-3423) BookKeeperJournalManager: NN startup is failing, when tries to recoverUnfinalizedSegments() a bad inProgress_ ZNodes
Date Thu, 17 May 2012 11:01:08 GMT

    [ https://issues.apache.org/jira/browse/HDFS-3423?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13277723#comment-13277723

Rakesh R commented on HDFS-3423:

In the patch I'm seeing only maxTxId.reset(maxTxId.get()-1); is invoked on SegmentEmptyException.
But I'm thinking about the inprogress_x ledgers which are not empty and had previously finalized
but not deleted.

The following code I have taken from BKJM. When l.verify(zkc, finalisedPath) == true, here
instead of storing the maxTxId and deleting the znode, we will only delete the inprogress_x
node as we had corresponding edit_x_y log file exists. IMHO, this is more safer. what's your

      try {
        l.write(zkc, finalisedPath);
      } catch (KeeperException.NodeExistsException nee) {
        if (!l.verify(zkc, finalisedPath)) {
          throw new IOException("Node " + finalisedPath + " already exists"
                                + " but data doesn't match");
      zkc.delete(inprogressPath, inprogressStat.getVersion());
> BookKeeperJournalManager: NN startup is failing, when tries to recoverUnfinalizedSegments()
a bad inProgress_ ZNodes
> --------------------------------------------------------------------------------------------------------------------
>                 Key: HDFS-3423
>                 URL: https://issues.apache.org/jira/browse/HDFS-3423
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>            Reporter: Rakesh R
>            Assignee: Ivan Kelly
>         Attachments: HDFS-3423.diff
> Say, the InProgress_000X node is corrupted due to not writing the data(version, ledgerId,
firstTxId) to this inProgress_000X znode. Namenode startup has the logic to recover all the
unfinalized segments, here will try to read the segment and getting shutdown.
> {noformat}
> EditLogLedgerMetadata.java:
> static EditLogLedgerMetadata read(ZooKeeper zkc, String path)
>       throws IOException, KeeperException.NoNodeException  {
>       byte[] data = zkc.getData(path, false, null);
>       String[] parts = new String(data).split(";");
>       if (parts.length == 3)
>          ....reading inprogress metadata
>       else if (parts.length == 4)
>          ....reading inprogress metadata
>       else
>         throw new IOException("Invalid ledger entry, "
>                               + new String(data));
>       }
> {noformat}
> Scenario:- Leaving bad inProgress_000X node ?
> Assume BKJM has created the inProgress_000X zNode and ZK is not available when trying
to add the metadata. Now, inProgress_000X ends up with partial information.

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