[Sidekiq zonal clusters - Redis] Documentation/operations
Prepare updates to existing documentation for how to operate these clusters including (but not limited to):
- How do we (re)size it in a hurry, or otherwise determine and manage the state of the cluster.
- What are upgrades like? Does the supplied chart make this easy and reliable, or would we rip/replace the entire sidekiq cluster (redis + workers) instead?
- Update all our tooling/runbooks to be multi-cluster capable. Consider a wrapper in the gitlab codebase (most of our examples simply use the console and built-in Sidekiq code); we'll have to teach the console nodes how to find all redis instances.