[jira] [Created] (HDFS-3386) Namenode is not deleting his lock entry '/ledgers/lock/lock-0000X', when fails to acquire the lock

["surendra singh lilhore (JIRA)" <ji...@apache.org>]

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:
{quote}
myznode = zkc.create(lockpath + "/lock-", new byte[] {'0'},
                                 Ids.OPEN_ACL_UNSAFE,
                                 CreateMode.EPHEMERAL_SEQUENTIAL);
if ((lockpath + "/" + nodes.get(0)).equals(myznode)) {
    if (LOG.isTraceEnabled()) {
        LOG.trace("Lock acquired - " + myznode);
    }
    lockCount.set(1);
    zkc.exists(myznode, this);
    return;
    } else {
        LOG.error("Failed to acquire lock with " + myznode
                        + ", " + nodes.get(0) + " already has it");
        throw new IOException("Could not acquire lock");
    }  
{quote}

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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