[KUDU-2200] Sanity-check that users specify the right number of masters when connecting

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 1.6.0
• Fix Version/s: 1.6.0
• Component/s: client, master, supportability
• Target Version/s: 1.6.0
• Assignee: Todd Lipcon
• Reporter: Todd Lipcon
• Created: 25/Oct/17 20:03
• Updated: 10/Jul/20 19:31
• Resolved: 02/Nov/17 05:39

Description

A common issue I've seen is that users set up an HA master setup (3 masters) but then in various cases only specify one of the masters when they try to connect using the client. This currently will work if it happens that they picked the leader master, and otherwise will return a s omewhat confusing "no leader" error message.

We should improve usability here by having the master send back a list of the master addresses in the case that it isn't the leader, and the client can use this to provide a more actionable error message like "Client connection specified only a subset of the cluster's masters" or somesuch.

I wouldn't want to automatically reconfigure the client and reconnect because this puts the client in a configuration state that will fail once the one master they specified goes down.