Please, provide config-mode: not configured yet

[unera]

Common architecture:

• Database - hosted on its own hosts
• 1..N applications - hosted on its own hosts

Note: Restarting (upgrade/reconfigure) process for each item is independent.

Now we have the database start algo:

1. load lua (PREREQUIRE stage)
2. load snapshot
3. recovery xlogs, connect the other replicas
4. apply config roles (load user's lua)

Note: tarantool listens port at point 1 but is fully configured only at (after) point 4.

So, for example, now tarantool can return several errors between points 1 and 4:

• No such function
• No such user | Auth error
• No such space
  etc

But if we remember common architecture paragraph, we can say that such errors are unexpected for common application.

"Network error" - is expected error, but "No such space" or "No such function" aren't!

So, it would be nice to add some config options for IPROTO

1. Delay all IPROTO-replies until config is fully done (excluding JOIN/SUBSCRIBE)
2. Return one (one!) documented error until config is fully done

[Totktonada]

See also 601bb92 and #3776.