What is the best solution for failover?

Question

High availability

There are 2 APP servers There are
2 redis servers It is
necessary that when the 1st (main) of the redis servers falls, the APP servers pick up a backup ip
Which method will be the most optimal and why:
1) failover (floating) IP between redis servers
2) keepalive on the APP server, followed by replacing the ip redis server
3) their crutches that primitively replace the "ip host" entry in /etc/hosts

Answer 1

And Redis Sentinel is not suitable?
https://redis.io/topics/sentinel