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Posted to dev@qpid.apache.org by "Keith Wall (JIRA)" <ji...@apache.org> on 2016/01/13 15:31:40 UTC

[jira] [Updated] (QPID-6996) Can't make a node master twice (during a single Broker lifetime)

     [ https://issues.apache.org/jira/browse/QPID-6996?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Keith Wall updated QPID-6996:
-----------------------------
    Summary: Can't make a node master twice (during a single Broker lifetime)  (was: Can't make a node master twice )

> Can't make a node master twice (during a single Broker lifetime)
> ----------------------------------------------------------------
>
>                 Key: QPID-6996
>                 URL: https://issues.apache.org/jira/browse/QPID-6996
>             Project: Qpid
>          Issue Type: Bug
>          Components: Java Broker
>    Affects Versions: 0.30, 0.32, qpid-java-6.0
>            Reporter: Keith Wall
>            Priority: Minor
>
> 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 not affected by this defect.



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