johnroach/ansible-gotchas

A list of gotchas of ansible

Ansible Gotchas, Tricks and Tools

Synopsis

TITLE Ansible Gotchas, Tricks and Tools

DESCRIPTION Ansible is a great configuration management tool. However like all tools there are certain aspects of it one must be aware of to fully utilize its capabilities and not to get stuck when a problem comes up. In this presentation we walk through examples of issues that were faced and solutions that was come up with. We will also be taking a look on some tools we can use to have a faster development cycle.

ABSTRACT Ansible documentation is well written however there are certain aspects of it that may not be immediately apparent to the developer. To this extent we will be go over the following subjects:

• Structure of an Ansible project
• Roles structure
• Playbook structure
• Playbook vs Role
• Host files (Parents and children)
• Variables and their scopes
• Roles and dependencies
• Templates
• Conditionals
• Tools: ansible-linter ansible-galaxy ansible-playbook --syntax-check ansible-playbook --list-hosts ansible-playbook --list-tasks ansible-playbook --list-tags ansible-playbook --step ansible-playbook --diff <-- awesome for templates

Demonstration

1. ansible-playbook -i hosts_one playbooks/structure.yml -v

   Notes: - Checkout the following: group_vars roles structure defaults meta tasks templates playbooks hosts_one

2. Move roles before task.

       ansible-playbook -i hosts_one playbooks/structure.yml -v
   

   Gotchas:

    - Roles run before tasks
   

3. Hosts and host groups

       ansible-playbook -i hosts_one playbooks/hosts.yml -v
       ansible-playbook -i hosts.d playbooks/hosts.yml -v
       ansible-playbook playbooks/hosts.yml -v
   

   Gotchas:

    - If using directory for hosts naming of host files are important. Example: change allhosts to zhosts
    - Just because you specified hosts in a sequence doesn't mean runs will be in a sequence
    - Specify your hosts file otherwise be ready to get the unexpected (i.e. /etc/ansible/hosts might get picked up!)
   

4. Variables

      ansible-playbook -i hosts.d playbooks/variables.yml -v
   

   Gotchas:

    - Ansible variable priority, its a thing!
   
   
    ```
        1.x, the precedence is as follows (with the last listed variables winning prioritization):
        “role defaults”, which lose in priority to everything and are the most easily overridden
        variables defined in inventory
        facts discovered about a system
        “most everything else” (command line switches, vars in play, included vars, role vars, etc.)
        connection variables (ansible_user, etc.)
        extra vars (-e in the command line) always win
    ```
   
    ```
        In 2.x, we have made the order of precedence more specific (with the last listed variables winning prioritization):
   
        role defaults
        inventory vars
        inventory group_vars
        inventory host_vars
        playbook group_vars
        playbook host_vars
        host facts
        play vars
        play vars_prompt
        play vars_files
        registered vars
        set_facts
        role and include vars
        block vars (only for tasks in block)
        task vars (only for the task)
        extra vars (always win precedence)
    ```
   
   
    - Variables can also be overwritten by roles if you are not careful. A good way around this is to use role name when defining variables.
   

5. Creating a role is pretty easy. Simply use ansible-galaxy tool like so:

   ansible-galaxy init roles/dependencies01

It is pretty awesome that they already have a tool for this. Simply fill in the blanks and have fun! Run the following line for this exercises:

ansible-playbook playbooks/dependencies.yml -v

Gotcha:

- Although it is cool to trust dependencies you must remember that if you are doing multiple plays in a single playbook your role might run twice.