Mastering Ansible

Chapter 1
• Host selection for plays and tasks
• Play and task names
Order of operations
Ansible is designed to be as easy as possible for a human to understand. The
developers strive to strike the best balance between human comprehension and
machine efficiency. To that end, nearly everything in Ansible can be assumed to be
executed in a top to bottom order; that is the operation listed at the top of a file will
be accomplished before the operation listed at the bottom of a file. Having said that,
there are a few caveats and even a few ways to influence the order of operations.
A playbook has only two main operations it can accomplish. It can either run a play,
or it can include another playbook from somewhere on the filesystem. The order
in which these are accomplished is simply the order in which they appear in the
playbook file, from top to bottom. It is important to note that while the operations are
executed in order, the entire playbook, and any included playbooks, is completely
parsed before any executions. This means that any included playbook file has to exist
at the time of the playbook parsing. They cannot be generated in an earlier operation.
Within a play, there are a few more operations. While a playbook is strictly ordered
from top to bottom, a play has a more nuanced order of operations. Here is a list of
the possible operations and the order in which they will happen:
• Variable loading
• Fact gathering
• The pre_tasks execution
• Handlers notified from the pre_tasks execution
• Roles execution
• Tasks execution
• Handlers notified from roles or tasks execution
• The post_tasks execution
• Handlers notified from post_tasks execution
Here is an example play with most of these operations shown:
---
- hosts: localhost
gather_facts: false
vars:
[ 13 ]