I'm running an ejabberd (20.04) node ejabberd@chat.example.com for the virtual host chat.example.com. It has MUC and PubSub enabled with hosts muc.chat.example.com and pubsub.chat.example.com, respectively. All that works fine.
Now I want to cluster the node, and add ejabberd@other.example.com as another node also serving the virtual host chat.example.com. That seems to work fine as well.
But I'm wondering what I need to do with MUC and PubSub. Should the second node also be configured with muc.chat.example.com and pubsub.chat.example.com and it will just work fine? Or do I need to configure custom hosts for the second node's mod_muc and mod_pubsub modules?
Well, I guess you can enable those modules in the new node too, with the same configuration than the first node, and ensure the table used by those modules is synchronized between both nodes. That would allow clients to create rooms in either node, and users of either node could join that room.