We are going to introduce the concept of multi-instance hosts in core.
Basically a host that will have two (or more) instances running on different ports.
This is needed for the goal to set up s8 and also to make sure we get the most out of our new and powerful hosts.
By doing this we'll be able to serve (with redundancy) recentchanges service for all the core shards with 8 hosts.
db2084 will be replicating s4 on port 3314 and s5 on port 3315
We would like know how to add it to mediawiki-config, and to confirm that mediawiki-config supports "HOST:PORT" syntax.
I have created a gerrit patch with that specific host db2084 so someone can actually review how it should be done to make sure this doesn't break the site: https://gerrit.wikimedia.org/r/385152
I have added a bunch of reviewers that I think that might help, but feel free to remove yourself if you are not sure you can.
Same with the project tags I have added.