Please see below. Thanks
Eric Mathias Herberts wrote: > >>Hi, I am in the process of evaluating ActiveMQ in HA topologies. I am >>currently doing some tests with the Master/Slave replication and I >>have a few questions: > >>Can the slave *catch up* if it is started some time after the master?, >>i.e. master is started at t0 for the first time, slave is started at >>t0+d also for the first time, will the slave be aware of every message >>persisted between t0 and t0+d? > [Eric] I think the answer is no. > >>If not how can a master and slave be synchronized either at startup or >>after a communication failure between the two? > [Eric] There is no way, it seems when Master starts up, it doesn't know > there will be a Slave, it just go ahead and answer its clients. When a > Slave comes up, it will register with Master, and the Master start send > msgs etc. to the Slave. But when there is communcation failure, the Master > simply drop the Slave and continue its work. The worse part is, when the > Slave restarts, it can still register with the Master, and work with the > Master again, but they two are out of sync. > >>I understand that the master will not answer its clients until the >>operation has been replicated to the slave(s), but since the master is >>not aware it has slaves until they come up, this whole master/slave >>replication is rather incomplete, i.e. the master will happily respond >>to its clients if the slave is not currently connecter, which makes >>the process rather useless in case of failure since the slave will not >>have a coherent view of the master's state. > [Eric] It seems to me the Master/Slave replication is not suitable for > production environment. > >>What would really be nice would be to have the following commands that >>could be passed to activemq: > >>- HOLD, freeze the state of the master >>- FLUSH, flush any data needing to persist to persistent storage, >>making the persistent storage stable and coherent. > >>this storage could then be replicated (using rsync for file based >>storage or using DB replication for DB based storage) on any number of >>slaves. > >>- RELEASE, unfreeze the master and resume current operations. > [Eric] It will be nice if we can have this. > >>Right now I do not see how to set up a secure DR topology ensuring >>coherent states on the slave. > >>Mathias. > > -- View this message in context: http://www.nabble.com/Master-Slave+questions-t1648743.html#a4472862 Sent from the ActiveMQ - User forum at Nabble.com.
