[ovs-discuss] Question to OVN DB pacemaker script

[Han Zhou]

Hi Babu/Numan,

I have a question regarding OVN pacemaker OCF script.
I see in the script MASTER_IP is used to start the active DB and standby
DBs will use that IP to sync from.

In the Documentation/topics/integration.rst it is also mentioned:

`master_ip` is the IP address on which the active database server is
expected to be listening, the slave node uses it to connect to the master
node.

However, since active node will change after failover, I wonder if we
should provide all the IPs of each nodes, and let pacemaker to decide which
IP is the master IP to be used, dynamically.

I see in the documentation it is mentioned about using the IPAddr2 resource
for virtual IP. Does it indicate that we should use the virtual IP as the
master IP? However, this may not work in all scenarios, since the virtual
IP works only if it can be routed to all nodes, e.g. when all nodes are on
the same subnet. In those cases the IPAddr2 virtual IP won't work. In those
cases, for the clients to access the DB, we can use Load-Balancer VIP. But
the problem is still how to set the master_ip and how to make the standby
to connect to the new active after failover.

I may have missed something here. Could you help explain what's the
expected way to work?

Thanks,
Han
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