This presentation is a fairly brief introduction to ansible including some minor details around WP Engine's implementation, variable precedence, a sample playbook, and some of the core concepts around what makes ansible tick.

1. INTRODUCING ANSIBLE
What is it? What do we do with it? How?!
Tyler Turk

2. Uh… What are we talking about?
• Configuration Management Utility
• Automation Utility
• Easily extensible and pluggable framework
• Michael DeHaan, 2012 (developer of cobbler)

3. Please sir, may I have some
more?
• Written in Python
• Used for server config management
• Used for auditing of environment

4. Server-CM: Ansible 1.7.3
Masterchief: Ansible 0.9

5. THE DYNAMIC INVENTORY

6. What are inventories? What do
they contain?
• List of groups
• List of hosts in groups
• Potentially some
variables

7. What’s our inventory?
• Dynamic inventory interface based off server-
meta
• inventory/server_meta.py
• Groups generated by:
• server-meta-ranges
• Datacenter values
• ansible_groups property

8. Currently Extant Groups
• 64b-pod
• hapod
• 4g
• 8g-legacy
• development
• staging
• production
• protostaging
• vendor_group
• cloud
• dedicated
• clusters

9. Managing Disparate
Environments
• Primary API services production
• Dev API services development
• Corporate servers are handled with a flat file

10. Why is the inventory important?
• Groups are managed by dynamic inventory
• Skipping dynamic inventory means no groups
• No groups means incorrect variables set
• Systems will be configured incorrectly

11. Why do we need a custom
inventory?
• Multi-vendor strategy
• Custom data
requirements
• Assurance of
environment isolation

12. INVENTORY PATTERN
MATCHING

13. Access The Servers You Want!
• ‘pod-*’ # All pods
• ‘utility-*’ # All servers
with utility in the name
• ‘cluster-*:!dbmaster*’ #
All servers in each
cluster excluding
dbmaster
• ‘vendor:&pod-*’ # All
pods that exist in vendor

14. A simple example

15. Another example with explicit inclusion

16. IMPORTANCE OF
IDEMPOTENCE

17. What is idempotence?
f(x) = f(f(x)) = f(f(f(f(f(f(x))))))
• property of certain
operations in
mathematics and
computer science, that
can be applied multiple
times without changing
the result beyond the
initial application
•f(x) = f(f(x))

18. Okay… why do we care?
• Less accident prone
• We don’t break things
• Playbook is repeatable
• Helps to ensure same state, each time

19. Examples
• Idempotent Task:
lineinfile: dest=/etc/hosts line=“127.0.01 localhost” state=present
• Non-Idempotent Task:
shell: echo “127.0.01 localhost” >> /etc/hosts

20. AD-HOC USAGE

21. Ansible Runner
Welcome to Ad-Hoc
Usage

22. Useful Modules
• Apt
• Command
• Copy
• Fetch
• File
• Service
• Shell
• Stat
• Template
• User
• Zabbix Maintenance

23. Issues with Bash-isms
• Complex audits can
require mixed quotations
• Susceptible to shell
limitations
• Use python wrapper to
avoid bash-isms

24. Command Examples
ansible -i inventory/server_meta.py -m shell -a ‘ls /nas/local/ssl’ vendor
ansible -f 50 -m shell -a 'grep mysql.heartbeat
/etc/zabbix/zabbix_agentd.conf | wc -l' -i inventory/server_meta.py 'cluster*'
&>heart.out
ansible -f 50 -m copy -a "src=/root/ssl_sucks/cloudflare.conf
dest=/etc/wpengine/nginx/ssl.d/cloudflare.conf owner=root group=root
mode=0644" -i inventory/server_meta.py 'pod-*:hapod-*:web-*'

25. WHAT IS THIS PLAYBOOK
SORCERY?

26. What are playbooks?
• List of tasks
• Run against subset of
hosts
• Hopefully idempotent

27. What’s in a playbook?
• Conditional task execution
• Hosts
• Notifiable handlers
• Roles
• Variables

28. Example Playbook

29. Server Provisioning Playbooks
• Remote Playbook:
• Executed remotely
• Handles partitioning
• Initial Configuration
• Copies files out
• Platform Playbook:
• Executed locally
• Facts from remote
• Ensures packages
• Completes Config

30. Platform Deployment Playbook
• phased-deploy:
• git prefetch
• git checkout
• ensures consistent
phases

31. One-Off Playbooks
• build-server.yml
• Handles build server provisioning
• fire_and_forget_pull.yml
• Similar to nas2-prefetch.yml
• prepare-loadtest.yml
• Stages the droid install on a server
• remove_user.yml
• Removes user from our infrastructure

32. VARIABLE PRECEDENCE &
TROUBLESHOOTING

33. Introduction to Ansible Variables
• Regular variables:
Variables that are
explicitly defined either
via register or various
files / CLI options
• Magic variables:
Variables that are
defined automatically

34. Some Magic Variables
• hostvars
• ansible_distribution
• ansible_INTERFACE
• ansible_fqdn
• ansible_pkg_mgr
• group_names
• inventory_hostname

35. Variable Precedence
• Defined on the CLI (-e, --extra-vars)
• Connection variables
• “Most everything else”
• Inventory variables
• Discovered facts
• Role defaults

36. Wait… “most everything else…?”
• Included variables
• Host variables
• Group Variables
• Child group
• Parent group
• “All” variables, the super parent
• Define a variable as few times as possible

37. Using Lookup Plugins for
Variables
• with_items - Iterate through a list of items
• with_dict - Iterate through a dictionary
• with_fileglob - Iterate through a glob of files
• with_first_found - Iterate through files until one
is found
• Create your own!

38. JINJA2 TEMPLATING
FRAMEWORK

39. Introduction to Templating
group_vars/all:
is_vagrant: false
roles/common/templates/etc/hosts:
{% if is_vagrant %}
192.168.1.1 api.wpengine.com
{% endif %}

40. How to Loop in Templates
roles/common/templates/etc/hosts:
{% for ip in ansible_all_ipv4_addresses | sort %}
{{ ip }} {{ ansible_fqdn }}
{% endfor %}
roles/common/templates/etc/ansible_groups:
{% for name in group_names | sort %}
{{ name }}
{% endfor %}

41. Conditionals and Extensions
roles/apache/templates/var/www/index.jn2:
<html><head>
{% if maintenance_mode | default('', false) | bool %}
{% include "maintenance_header.html" %}
{% else %}
<title>Production - Ansible
Example</title></head><body>
<h3>Production mode FTW!</h3>
{% endif %}
</body></html>

42. Simple Demo Time!
ansible-playbook sample.yml
ansible-playbook sample.yml -e "maintenance_mode=false"
ansible-playbook sample.yml -e “maintenance_mode=true"
file:///Users/tylerturk/meetup/output/index.html

43. I WANT MORE OUT OF IT

44. Possible to Extend Upon
• Additional plugins can easily be dropped in
• Researching sample plugins goes a long way
• Several different plugin types currently
available
• Return results in JSON or hook however you
choose

45. Got questions? Ask!
Examples Available At:
https://github.com/tylerturk/ansible-examples-
jan28
Twitter: tylerjturk