Change Details

Spun off from T114271. We need scripts and processes to do a planned switch from master datacenter A to B: a) Go read-only on the app level (mostly MediaWiki) b) Make sure write traffic stops c) Go read-only for all data stores d) Wait for all data stores in the B datacenter to catch up and be in sync with A e) Make the B datacenter the new master datacenter (systems and app level) f) End read-only mode Read-only mode should be as short as possible so we can actually test this.