Describe the problem

The raft.Ready contract has some deficiencies that have caused trouble upstream, and which are in our interest to help resolve.

etcd-io/etcd#14370 (comment)

I believe we're not affected, since we are aware of this behavior and handle it:

To Reproduce

See the thread above.

Expected behavior

Make the single-node case look like any other case. Don't emit Ready with .CommittedEntries that are contingent on handling .Entries. This reduces single-node throughput, but the performance could be clawed back on our end by special casing single nodes (which we probably don't need to, since if performance is a goal we can more completely elide raft).

In practice, this means shepherding etcd-io/etcd#14411.

Also revive etcd-io/etcd#10861, which among other things points out the above problem.

When thinking about issues such as these:

#38322
#17500 (comment)

it is important to have all of the invariants properly documented and discoverable.

Jira issue: CRDB-19244