[ClusterLabs] Retrofit MySQL with pacemaker?

[Strahil Nikolov]

On May 3, 2020 11:47:35 AM GMT+03:00, "Niels Kobschätzki" <niels at kobschaetzki.net> wrote:
>Hi,
>
>I have here several master/slave-MySQL-instanced which I want to
>retrofit with corosync/Pacemaker while they are in production and I
>want to do it with minimal downtime. 
>Is that even possible?
>
>I would set up a 2-node corosync-cluster on both. Then I have the
>problem that there is already a virtual IP and I want to continue using
>it. Do I deco figure the VIP on the current active master, then
>configure the resource? Or is there a better way. How would I go in
>configuring the MySQL-resource?
>
>Did anyone here did something like that before or do you always start
>with a new setup (which begs the question how do you get the data from
>the old to the new - dump it out or can you attach the new one to the
>old one somehow and then switch at a certain point?)?
>
>Best,
>
>Niels
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Hi Niels,

I believe that you can do it even without downtime but it will be hard to do it.

Most probably something like this can work, but I have never done it:
1. Setup and install the cluster without the resources
2. Set the cluster in maintenance
3. Either use the shadow cib or pcs counterpart command to define the whole cluster
4. Load the shadow cib from the file
5. Run a crm_simulate to verify the cluster's actions
6. Remove the maintenance

A more safer approach is to create the cluster with the replication in advance and then either use replication to transfer the data or use an export/import for that purpose.

If you have a spare pair of systems , you can try the first approach (building a fresh cluster and configure it while the DB is running).

Best Regards,
Strahil Nikolov