[jira] [Created] (QPID-6996) Can't change make a node master twice

["Keith Wall (JIRA)" <ji...@apache.org>]

Keith Wall created QPID-6996:
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             Summary: Can't change make a node master twice 
                 Key: QPID-6996
                 URL: https://issues.apache.org/jira/browse/QPID-6996
             Project: Qpid
          Issue Type: Bug
          Components: Java Broker
    Affects Versions: qpid-java-6.0, 0.32, 0.30
            Reporter: Keith Wall


The Java Broker's BDB HA implementation permits the mastership to be transferred around the group.  To initiate this change, a user mutates the model attribute "role" on object {{BDBHAVHN}} or {{BDBHARRN}} to have the value {{MASTER}} through a management interface.

If I make this change once, the change is effective.  If later the mastership moves again (as a result of a failure and subsequent election or a transfer master elsewhere in the group), the attempt to move the mastership back to this node is ignored (defect).

The issue is that ACO#changeAttributes blocks the subsequent change because it does not know that attribute's value is anything other than {{MASTER}}.  This is because BDBHAVHN#setRole (happens asynchronously as the mastership changes) updates only the CO view of the attribute (#_role), leaving ACO#_attributes.get(ROLE) with a stale value {{MASTER}}.  The Broker containing the node needs to be bounce to correct the state problem.

The main use-case for transfer master is to restore the master to its business as usual position following a device failure.  This use-case is affected by this defect.



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