Let user specify some replicas as voters and some as non-voters

[timmaxw]

In raft right now, consensus is defined as a majority of all replicas. We should let the user specify replicas that aren't used for consensus. This could take the form of another field in table_config called non_voting_replicas, or something.

[danielmewes]

What's an example use case of this?

[timmaxw]

Suppose the user has three replicas in a datacenter in Boston and one replica in each of three "satellite" datacenters in San Francisco, Hong Kong, and Paris. The primaries are all in the Boston datacenter, and the user wants writes to be acknowledged without doing a complete network round-trip to one of the remote datacenters. So they set the satellite replicas as non-voting.

[danielmewes]

Got it, thanks

[VeXocide]

Moving to the raft milestone due to #3894.

[danielmewes]

I think it's actually not critical that we support this for #3894 . Just single and majority acks should be enough for the first release.

We might get this as a side effect of implementing hard override, but in itself I think it's not release critical.

[VeXocide]

👍

[deontologician]

This is just a reminder to do the webui portion whenever this is completed

[timmaxw]

In CR 2925.

[deontologician]

@timmaxw so do we need new webui functionality for this in your opinion?

[timmaxw]

The web UI should visually indicate which replicas are nonvoting, but other than that I don't think we need anything.

[danielmewes]

The web UI should visually indicate which replicas are nonvoting, but other than that I don't think we need anything.

👍

[timmaxw]

Fixed in f706b90.