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Merge branch 'RefreshBestPractices' of https://github.com/tbielawa/ansible.github.com

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Michael DeHaan 2012-08-09 22:11:42 -04:00
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rst/bestpractices.rst
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@ -6,15 +6,16 @@ Here are some tips for making the most of Ansible.
Always Mention State
++++++++++++++++++++
The 'state' parameter is optional to a lot of modules. Whether state=present or state=absent, it's always
best to leave that parameter in your playbooks to make it clear, especially as some modules support additional
states.
The 'state' parameter is optional to a lot of modules. Whether
'state=present' or 'state=absent', it's always best to leave that
parameter in your playbooks to make it clear, especially as some
modules support additional states.
Group By Roles
++++++++++++++
A system can be in multiple groups. See :doc:`patterns`. Having groups named after things like
'webservers' and 'dbservers' is repeated in the examples because it's a very powerful concept.
*webservers* and *dbservers* is repeated in the examples because it's a very powerful concept.
This allows playbooks to target machines based on role, as well as to assign role specific variables
using the group variable system.
@ -24,38 +25,32 @@ Directory Organization
Playbooks should be organized like this::
(root of source control repository)
# root of source control repository
├── acme/
│ ├── setup.yml
│ └── stop.yml
├── files/
│ └── some_file_path_foo.conf
├── handlers/
│ └── main.yml
├── tasks/
│ ├── setup.yml
│ └── stop.yml
├── templates/
│ ├── etc_acme_conf_acme.conf
│ └── etc_other_conf_other.conf
├── vars/
│ └── main.yml
└── global_vars.yml
global_vars.yml # variables for all playbooks
acme/ # each playbook has a directory
setup.yml # playbook to manage the service
stop.yml # playbook to halt the service (optional)
files/
some_file_path_foo.conf
templates/
etc_acme_conf_acme.conf
etc_other_conf_other.conf
vars/
main.yml # variables specific to this playbook
handlers/
main.yml
tasks/
setup.yml
stop.yml
Any directories or files not needed can be omitted. Not all modules may require `vars` or `files` sections, though most
will require `handlers`, `tasks`, and `templates`. To review what each of these sections do, see :doc:`playbooks` and :doc:`playbooks2`.
Any directories or files not needed can be omitted. Not all modules
may require 'vars' or 'files' sections, though most will require
'handlers', 'tasks', and 'templates'. To review what each of
these sections do, see :doc:`playbooks` and :doc:`playbooks2`.
The acme/setup.yml playbook would be as simple as::
----
---
- hosts: webservers
user: root
@ -73,7 +68,9 @@ when things change, and these are described in :doc:`playbooks`.
Including more than one setup file or more than one handlers file is of course legal.
Having playbooks be able to include other playbooks is coming in a future release. See Issue 538.
Having playbooks be able to include other playbooks is coming in a
future release. See `Issue 538
<https://github.com/ansible/ansible/issues/538>`_.
Until then, to manage your entire site, simply execute all of your playbooks together, in the order desired.
You don't have to do this though. It's fine to select sections of your infrastructure to manage at a single time.
@ -92,23 +89,45 @@ keep modules that go with a playbook together.
Miscellaneous Tips
++++++++++++++++++
When you can do something simply, do something simply. Do not reach to use every feature of Ansible together, all
at once. Use what works for you. For example, you should probably not need ``vars``, ``vars_files``, ``vars_prompt`` and ``--extra-vars`` all at once, while also using an external inventory file.
When you can do something simply, do something simply. Do not reach
to use every feature of Ansible together, all at once. Use what works
for you. For example, you should probably not need 'vars',
'vars_files', 'vars_prompt' and '--extra-vars' all at once,
while also using an external inventory file.
Optimize for readability. Whitespace between sections of YAML documents and in between tasks is strongly encouraged,
as is usage of YAML comments, which start with "#". It is also useful to comment at the top of each file the purpose of the individual file and the author, including email address.
Optimize for readability. Whitespace between sections of YAML
documents and in between tasks is strongly encouraged, as is usage of
YAML comments, which start with '#'. It is also useful to comment
at the top of each file the purpose of the individual file and the
author, including email address.
It is possible to leave off the "name" for a given task, though it is recommended to provide
a descriptive comment about why something is being done instead.
It is possible to leave off the 'name' for a given task, though it
is recommended to provide a descriptive comment about why something is
being done instead.
Use version control. Keep your playbooks and inventory file in git (or another version control system), and commit when you make changes to them.
This way you have an audit trail describing when and why you changed the rules automating your infrastructure.
Use version control. Keep your playbooks and inventory file in git
(or another version control system), and commit when you make changes
to them. This way you have an audit trail describing when and why you
changed the rules automating your infrastructure.
Resist the urge to write the same playbooks and configuration files for heterogeneous distributions. While lots of software packages claim to make this easy on you, the configuration files are often quite different, to the point where it would be easier to treat them as different playbooks. This is why, for example, Ansible has a seperate 'yum' and 'apt' module. Yum and apt have different capabilities, and we don't want to code for the least common denominator.
Resist the urge to write the same playbooks and configuration files
for heterogeneous distributions. While lots of software packages
claim to make this easy on you, the configuration files are often
quite different, to the point where it would be easier to treat them
as different playbooks. This is why, for example, Ansible has a
separate :ref:`yum` and :ref:`apt` module. Yum and apt have different
capabilities, and we don't want to code for the least common
denominator.
Use variables for user tunable settings versus having constants in the tasks file or templates, so that it is easy to reconfigure a playbook. Think about this as exposing the knobs to things you would like to tweak.
Use variables for user tunable settings versus having constants in the
tasks file or templates, so that it is easy to reconfigure a playbook.
Think about this as exposing the knobs to things you would like to
tweak.
Since a system can be in more than one group, if you have multiple datacenters or sites, consider putting systems into groups by role, but also different groups by geography. This allows you to assign different variables to different geographies.
Since a system can be in more than one group, if you have multiple
datacenters or sites, consider putting systems into groups by role,
but also different groups by geography. This allows you to assign
different variables to different geographies.
.. seealso::
@ -126,5 +145,3 @@ Since a system can be in more than one group, if you have multiple datacenters o
Complete playbook files from the github project source
`Mailing List <http://groups.google.com/group/ansible-project>`_
Questions? Help? Ideas? Stop by the list on Google Groups