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calmdev/pedantically_commented_playbook.yml

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Created January 6, 2014 03:20
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pedantically_commented_playbook.yml
---
# ^^^ YAML documents must begin with the document separator "---"
#### Example docblock, I like to put a descriptive comment at the top of my
#### playbooks.
#
# Overview: Playbook to bootstrap a new host for configuration management.
# Applies to: production
# Description:
# Ensures that a host is configured for management with Ansible.
#
###########
###########
#
#
# Note:
# YAML, like Python, cares about whitespace. Indent consistently throughout.
# Be aware! Unlike Python, YAML refuses to allow the tab character for
# indentation, so use spaces.
#
# Two-space indents feel comfortable to me, but do whatever you like.
#
# If you're new to YAML, keep in mind that YAML documents, like XML
# documents, represent a tree-like structure of nodes and text. More
# familiar with JSON? Think of YAML as a strict and more flexible JSON
# with fewer significant characters (e.g., :, "", {}, [])
#
# The curious may read more about YAML at:
# http://www.yaml.org/spec/1.2/spec.html
#
###
# Notice the minus on the line below -- this starts the playbook's record
# in the YAML document. Only one playbook is allowed per YAML file. Indent
# the body of the playbook.
-
hosts: all
# Playbook attribute: hosts
# Required: yes
# Description:
# The name of a host or group of hosts that this playbook should apply to.
#
## Example values:
# hosts: all -- applies to all hosts
# hosts: hostname -- apply ONLY to the host 'hostname'
# hosts: groupname -- apply to all hosts in groupname
# hosts: group1,group2 -- apply to hosts in group1 & group2
# hosts: group1,host1 -- mix and match hosts
# hosts: *.mars.nasa.gov wildcard matches work as expected
#
## Using a variable value for 'hosts'
#
# You can, in fact, set hosts to a variable, for example:
#
# hosts: $groups -- apply to all hosts specified in the variable $groups
#
# This is handy for testing playbooks, running the same playbook against a
# staging environment before running it against production, occasional
# maintenance tasks, and other cases where you want to run the playbook
# against just a few systems rather than a whole group.
#
# If you set hosts as shown above, then you can specify which hosts to
# apply the playbook to on each run as so:
#
# ansible-playbook playbook.yml --extra-vars="groups=staging"
#
# Use --extra-vars to set $groups to any combination of groups, hostnames,
# or wildcards just like the examples in the previous section.
#
sudo: True
# Playbook attribute: sudo
# Default: False
# Required: no
# Description:
# If True, always use sudo to run this playbook, just like passing the
# --sudo (or -s) flag to ansible or ansible-playbook.
# Playbook attribute: user
# Default: "root'
# Required: no
# Description
# Remote user to execute the playbook as
user: remoteuser
# Playbook attribute: vars
# Default: none
# Required: no
# Description:
# Set configuration variables passed to templates & included playbooks
# and handlers. See below for examples.
vars:
color: brown
web:
memcache: 192.168.1.2
httpd: apache
# Tree-like structures work as expected, but be careful to surround
# the variable name with ${} when using.
#
# For this example, ${web.memcache} and ${web.apache} are both usable
# variables.
########
# A possible gotcha!
#
# Variables do not expand inside the 'vars' section.
#
# The following will not work. $config_path will be set to the string
# "/etc/$config" NOT "/etc/ntpd.conf". This is expected behavior
# and won't be fixed. Be explicit about the values of your variables.
config: ntpd.conf
config_path: /etc/$config
########
# Variables can be set conditionally. This is actually a tiny snippet
# of Python, so be sure to quote any $vars and make the expression
# always evaluate to True or False.
is_color_blue: "'$color' == 'blue'"
#####
# TODO: Document useful builtin vars
# $inventory_hostname
# Playbook attribute: vars_files
# Require: no
# Description:
# Specifies a list of YAML files to load variables from.
#
# Always evaluated after the 'vars' section, no matter which section
# occurs first in the playbook. Examples are below.
#
# Example YAML for a file to be included by vars_files:
# ---
# - monitored_by: phobos.mars.nasa.gov
# - fish_sticks: "good with custard"
# # (END OF DOCUMENT)
#
# Remove the indentation & comments of course, the '---' should be at
# the left margin in the variables file.
#
vars_files:
# Include a file from this absolute path
- /srv/ansible/vars/vars_file.yml
# Include a file from a path relative to this playbook
- vars/vars_file.yml
# By the way, variables set in 'vars' are available here.
- vars/$hostname.yml
# TODO: test, are vars_prompt variables available here?
# It's also possible to pass an array of files, in which case
# Ansible will loop over the array and include the first file that
# exists. If none exist, ansible-playbook will halt with an error.
#
# An excellent way to handle platform-specific differences.
- [ vars/$platform.yml, vars/default.yml ]
# Playbook attribute: vars_prompt
# Required: no
# Description:
# A list of variables that must be manually input each time this playbook
# runs. Used for sensitive data and also things like release numbers that
# vary on each deployment. Ansible always prompts for this value, even
# if it's passed in through the inventory or --extra-vars.
#
# The input won't be echoed back to the terminal.
#
# TODO: I think that the value is supposed to show as a prompt but this
# doesn't work in the latest devel
#
vars_prompt:
passphrase: "Please enter the passphrase for the SSL certificate"
# Not sensitive, but something that should vary on each playbook run.
release_version: "Please enter a release tag"
# TODO: find out if ansible prompts even when var is passed in --extra-vars
# Playbook attribute: tasks
# Required: yes
# Description:
# A list of tasks to perform in this playbook.
tasks:
##########
# The simplest task
# Each task must have a name & action.
- name: Check that the server's alive
action: ping
##########
# Ansible modules do the work!
- name: Enforce permissions on /tmp/secret
action: file path=/tmp/secret mode=0600 owner=root group=root
#
# Format 'action' like above:
# <modulename> <module parameters>
#
# Test your parameters using:
# ansible -m <module> -a "<module parameters>"
#
# Documentation for the stock modules:
# http://ansible.github.com/modules.html
##########
# Use variables in the task!
#
# Variables expand in both name and action
- name: Paint the server $color
action: command echo $color
##########
# Trigger handlers when things change!
#
# Ansible detects when an action changes something. For example, the
# file permissions change, a file's content changed, a package was
# just installed (or removed), a user was created (or removed). When
# a change is detected, Ansible can optionally notify one or more
# Handlers. Handlers can take any action that a Task can. Most
# commonly they are used to restart a service when its configuration
# changes. See "Handlers" below for more about handlers.
#
# Handlers are called by their name, which is very human friendly.
# This will call the "Restart Apache" handler whenever 'copy' alters
# the remote httpd.conf.
- name: Update the Apache config
action: copy src=httpd.conf dest=/etc/httpd/httpd.conf
notify: Restart Apache
# Here's how to specify more than one handler
- name: Update our app's configuration
action: copy src=myapp.conf dest=/etc/myapp/production.conf
notify:
- Restart Apache
- Restart Redis
##########
# Include tasks from another file!
#
# Ansible can include a list of tasks from another file. The included file
# must represent a list of tasks, which is different than a playbook.
#
# See new_user.yml for an example.
# TODO: actually make the example
#
# In this example $user will be 'sklar'
# and $color will be 'red' when evaluating new_user.yml
- include: tasks/new_user.yml user=sklar color=red
# Good, generic playbooks can be used multiple times:
- include: tasks/new_user.yml user=mosh color=mauve
# Variables expand before the include is evaluated:
- include: tasks/new_user.yml user=chris color=$color
##########
# Run a task on each thing in a list!
#
# Ansible provides a simple loop facility. If 'with_items' is provided for
# a task, then the task will be run once for each item in the 'with_items'
# list. $item changes each time through the loop.
- name: Create a file named $item in /tmp
action: command touch /tmp/$item
with_items:
- tangerine
- lemon
##########
# Choose between files or templates!
#
# Sometimes you want to choose between local files depending on the
# value of the variable. first_available_file checks for each file
# and, if the file exists calls the action with $item={filename}.
#
# Mostly useful for 'template' and 'copy' actions. Only checks local
# files.
#
- name: Template a file
action: template src=$item dest=/etc/myapp/foo.conf
first_available_file:
# ansible_distribution will be "ubuntu", "debian", "rhel5", etc.
- templates/myapp/${ansible_distribution}.conf
# If we couldn't find a distribution-specific conf, then use default.conf:
- templates/myapp/default.conf
##########
# Conditionally execute tasks!
#
# Sometimes you only want to run an action when a under certain conditions.
# Ansible will 'only_if' as a Python expression and will only run the
# action when the expression evaluates to True.
#
# If you're trying to run an # task only when a value changes,
# consider rewriting the task as a notification.
#
- name: "shutdown if my favorite color is blue"
action: command /sbin/shutdown -t now
only_if: '$is_color_blue'
# (See the vars section above for how we set $is_color_blue)
##########
#
# TODO: figure out how 'connection: local' works, document 'user' and other attributes
# TODO: finish this example, write a handler section
# vim:ff=unix ts=2 sw=2 ai expandtab
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