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From "surendra singh lilhore (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HDFS-3386) Namenode is not deleting his lock entry '/ledgers/lock/lock-0000X', when fails to acquire the lock
Date Tue, 08 May 2012 14:45:48 GMT
surendra singh lilhore created HDFS-3386:

             Summary: Namenode is not deleting his lock entry '/ledgers/lock/lock-0000X',
when fails to acquire the lock
                 Key: HDFS-3386
                 URL: https://issues.apache.org/jira/browse/HDFS-3386
             Project: Hadoop HDFS
          Issue Type: Bug
          Components: ha
            Reporter: surendra singh lilhore
            Priority: Minor
             Fix For: 0.23.0

When a Standby NN becomes Active, it will first create his sequential lock entry create lock-000X
 in ZK and then tries to acquire the lock as shown below:
myznode = zkc.create(lockpath + "/lock-", new byte[] {'0'},
if ((lockpath + "/" + nodes.get(0)).equals(myznode)) {
    if (LOG.isTraceEnabled()) {
        LOG.trace("Lock acquired - " + myznode);
    zkc.exists(myznode, this);
    } else {
        LOG.error("Failed to acquire lock with " + myznode
                        + ", " + nodes.get(0) + " already has it");
        throw new IOException("Could not acquire lock");

Say the transition to standby fails to acquire the lock it will throw the exception and NN
is getting shutdown. Here the problem is, the lock entry lock-000X will exists in the ZK till
session expiry and the further start-up will not be able to acquire lock.

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