Check out the HA Cluster Setup in the docs:
From what I can see, you can only point an Alpha at one Zero… if that zero goes down, what happens to that alpha instance? Can it still communicate with the other two Zeros? After connecting to one Zero, does it then get the connection info for all of the Zeros?
In the docs:
The new Alphas will automatically detect each other by communicating with Dgraph zero and establish connections to each other.
I’m not a dgraph expert, but I think it’s not so bad to run with an alpha and zero on the same host because they operate independently (more specifically they have independent HA). But there may be other reasons to avoid that - e.g. resource contention.