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Re: Expanding Galera cluster



SET GLOBAL wsrep_desync=1 will set a node as desynced and will cause
MaxScale to stop sending traffic to it (provided you use
router_options=synced in your maxscale.cnf config file)


On Mon, Jul 4, 2016 at 11:25 AM Thorvald Hallvardsson <
thorvald.hallvardsson@xxxxxxxxx> wrote:

> Hi guys,
> I need some help as I'm preparing to expand my existing Galera cluster.
> Generally the purpose of it is I need to replace 3 VMs I have a cluster
> running on to 2 physical servers I have been given for that purpose.
> My idea was to join 2 physical cluster to the existing cluster of 3 and
> then remove all 3 VMs from the cluster leaving 2 physical nodes within. I
> have a arbitrator box within the cluster as well.
> The config at the moment contains 2 maxscale proxy nodes on the front
> balancing the read queries across the entire cluster of 3 and write queries
> to the elected master.
> What I want to achieve is as I said above but + I will need another help
> with maxscale to expand and then shrink the cluster down to 2 nodes
> afterwards. I have had a situation before when I had to do a simple config
> change on the Galera cluster and I was trying to mark nodes and put them
> into maintenance mode to stop traffic coming to them but the commands like
> set server NODE master didn't actually do anything. I had situations when I
> had 2 masters in the cluster for a second because then something was
> happening that my manually selected master was becoming a slave again. I
> couldn't find anything on the internet what would point me into right
> direction and explain the whole procedure in details.
> My cluster is quite busy at the moment even overnight so there is no
> perfect time to do anything on it. I need to do it the least disruptive way
> and the most controlled way as well. Hence I'm asking for help and
> suggestions as I found both Galera and maxscale documentation very very
> brief not actually providing any decent details or procedures. I found much
> more help from Percona but descriptions don't match sometimes.
> Please help.
> Regards,
> TH
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Guillaume Lefranc
Remote DBA Services Manager
MariaDB Corporation

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