For switching over the appservers, we need to do the following:
- Make it easy to switch the configuration of mediawiki to have a different primary datacenter (see T114273)
- Correct all the things that are eqiad-only in mediawiki-config (there are many, introduced after we got it on par...)
- Perform a quick sanity check of performance of a sample of pages in the two DCs
- Check the amount of resources available in the various clusters - codfw was sized as a slightly reduced eqiad at the time, but we did change some ratios in eqiad in the meantime.
See also: Why they're doing this https://meta.wikimedia.org/wiki/Tech/Server_switch_2016