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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