High availability with multiple Masters

The traditional Salt setup only involves a single Master with multiple Minions. This is fine for a number of smaller shops, and even some of the bigger ones, but definitely not for everybody. High availability has become increasingly crucial in the modern infrastructure, and Salt is a part of that.

Built-in high availability configuration

Salt does have a little built-in configuration to handle multiple Masters, but it's smaller and simpler than what one might expect. Interestingly, the actual Salt configuration is all on the Minion; the Masters don't have any configuration inside of Salt itself. We'll talk about that in a moment.

First, let's talk about Minion configuration. Normally, Minions have a single Master defined in their configuration file:

master: 10.0.0.10

However, a list of Masters may be defined instead:

master:
  - 10.0.0.10
  - 10.0.0.11

There is no imposed limit to how many Masters may be declared for a single Minion...