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From "James Strachan" <>
Subject Re: temporary queue in store and forward environment
Date Mon, 30 Apr 2007 08:41:30 GMT
On 4/29/07, DavidR <> wrote:
> Ok, so if we go back to Master Slave, then we have the following issue:
> Currently we are using the JDBC Master Slave but we see this uses a lot of
> CPU.
> So, we would want to go to pure Master Slave.
> So, can you help us understand the following: It says in the docs that if
> one goes down "A failed master cannot be re-introduced without shutting down
> the the slave broker". Can it be re-introduced as a slave without any
> restart of the running queue?

The issue is we don't have a real time broker-broker synchronization
mechanism yet for pure master/slave. So you can start up 2 brokers in
a master/slave; if the master fails the slave takes over just fine.
But if you wish to introduce another slave/master to the master after
failover, you need to stop the broker & copy its files to the new
location. We don't yet have a way to dynamically bring a new cluster
member online to a running cluster.

>  Also, if the slave had items in the queue not
> processes and then came up as slave, what would happen with those messages?

All kinds of issues would arise if you brought up an old master/slave
into a running master/slave cluster without synchronizing. e.g. ACKs
could be missed so messages could be duplicated - plus messages could
be lost.


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