Docker cluster for newby

Hello everyone

I’m starting with docker, and at the moment it seems fantastic

I’m with swarm, and here I have a couple of questions

The first thing is, I create a service, with 5 replicas of an httpd, for example. How can I prove the high availability of that claster, that is, I understand that it works if the replicas are falling, or that it balances

Can anyone clear that doubt?