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From Robbie Gemmell <robbie.gemm...@gmail.com>
Subject Re: Qpid Java Broker - Master Failure and Recovery
Date Tue, 06 Aug 2013 20:38:59 GMT
The helper node details in the XML are only used when initialising the
store for the first time, i.e when creating the cluster for the first node
(by specifying itself as the helper), or joining the pre-existing cluster
(by specifying an existing node as the helpder) for the rest. Once you
initialise BDB HA, the cluster information is stored *inside* the log files
it creates, and if these files still exist when the node is restarted then
that embedded cluster information is used to identify where the members of
the cluster are and communicate with them without the use of a specific
helper, thus ignoring the helper node information passed via the XML.

If you should happen to delete the store files for the node that created
the cluster (i.e the very original master, which which has XML
configuration pointing at itself, call it NodeA) and then want to restart
that node and have it rejoin the cluster (which still exists because the
other node, call it NodeB, has retained its store files) then you would
need to update the configuration of NodeA to supply the details of an
existing node as the helper, i.e NodeB. On the other hand, if NodeA
retained its files but you deleted the NodeB files, when you restarted it
you wouldn't need to edit the configuration since it already points at an
existing node of the cluster, Node A.

For more information, see the first of the pages on the Oracle site that I
linked to earlier:


On 6 August 2013 21:11, jbelch <jamesbelch@verizon.net> wrote:

> But how does the old "MASTER" that failed know what port to connect to as
> the
> HelperHostPort?  Is the new HelperHostPort the new "MASTER":5001 even
> though
> the jconsole still displays it as the old "MASTER".
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