Mastering Ansible

Chapter 1
As we can see, both hosts backend.example.name and mastery.example.name
were operated on. Let's see what happens if we supply a limit, specifically to limit
our run to only frontend systems:
We can see that only mastery.example.name was operated on this time. While there
are no visual clues that the entire inventory was parsed, if we dive into the Ansible
code and examine the inventory object, we will indeed find all the hosts within, and
see how the limit is applied every time the object is queried for items.
It is important to remember that regardless of the host's pattern used in a play, or the
limit supplied at runtime, Ansible will still parse the entire inventory set during each
run. In fact, we can prove this by attempting to access host variable data for a system
that would otherwise be masked by our limit. Let's expand our playbook slightly and
attempt to access the ansible_ssh_port variable from backend.example.name:
---
- name: limit example play
hosts: all
gather_facts: false
tasks:
- name: tell us which host we are on
debug:
var: inventory_hostname
- name: grab variable data from backend
debug:
var: hostvars['backend.example.name']['ansible_ssh_port']
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