Ansible is a great tool to setup multiple servers in a consistent reproducible way. It is easy to setup a complete cluster or a complex software architecture running on multiple machines. But some tasks only need to be executed once. For example you can setup a complete cluster of DB servers, but the table definitions/content only needs to be done once, after the cluster is running. Since the goal of Ansible is to always end with a consistent state it should be OK to run the same task multiple times, without breaking your setup (idempotent), but if you setup a bigger cluster with Hundertes of nodes, you would definitely want to avoid running the same task over and over again, if this can be avoided.
There a basically two options that you can use to ensure a task is executed only once.
