How do I select the master Redis pod in this Kubernetes example?

Here's the example I have modeled after.

In the Readme's "Delete our manual pod" section:

3. The redis sentinels themselves, realize that the master has disappeared from the cluster, and begin the election procedure for selecting a new master. They perform this election and selection, and chose one of the existing redis server replicas to be the new master.

How do I select the new master? All 3 Redis server pods controlled by the redis replication controller from redis-controller.yaml still have the same

labels:
  name: redis

which is what I currently use in my Service to select them. How will the 3 pods be distinguishable so that from Kubernetes I know which one is the master?

via writofmandamus