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From "ASF subversion and git services (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (QPID-6996) Can't make a node master twice (during a single Broker lifetime)
Date Fri, 15 Jan 2016 15:55:39 GMT

    [ https://issues.apache.org/jira/browse/QPID-6996?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15101960#comment-15101960

ASF subversion and git services commented on QPID-6996:

Commit 1724844 from orudyy@apache.org in branch 'java/trunk'
[ https://svn.apache.org/r1724844 ]

QPID-6996: Set property 'updateAttributeDespiteUnchangedValue' on role attribute in BDB HA
RemoteReplicationNode and add system tests

> 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
>         Attachments: roleChangePatch.diff, roleChangePatch2.diff
> 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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