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143 lines
5.1 KiB
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Best Practices
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==============
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Here are some tips for making the most of Ansible.
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.. contents::
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:depth: 2
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:backlinks: top
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Always Mention State
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++++++++++++++++++++
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The 'state' parameter is optional to a lot of modules. Whether
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'state=present' or 'state=absent', it's always best to leave that
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parameter in your playbooks to make it clear, especially as some
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modules support additional states.
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Group By Roles
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++++++++++++++
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A system can be in multiple groups. See :doc:`patterns`. Having groups named after things like
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*webservers* and *dbservers* is repeated in the examples because it's a very powerful concept.
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This allows playbooks to target machines based on role, as well as to assign role specific variables
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using the group variable system.
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Directory Organization
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++++++++++++++++++++++
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Playbooks should be organized like this::
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# root of source control repository
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├── acme/
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│ ├── setup.yml
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│ └── stop.yml
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├── files/
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│ └── some_file_path_foo.conf
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├── handlers/
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│ └── main.yml
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├── tasks/
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│ ├── setup.yml
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│ └── stop.yml
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├── templates/
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│ ├── etc_acme_conf_acme.conf
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│ └── etc_other_conf_other.conf
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├── vars/
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│ └── main.yml
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└── global_vars.yml
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Any directories or files not needed can be omitted. Not all modules
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may require 'vars' or 'files' sections, though most will require
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'handlers', 'tasks', and 'templates'. To review what each of
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these sections do, see :doc:`playbooks` and :doc:`playbooks2`.
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The acme/setup.yml playbook would be as simple as::
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---
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- hosts: webservers
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user: root
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vars_files:
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- ../global_vars.yml
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- vars/main.yml
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tasks:
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- include: tasks/setup.yml
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handlers:
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- include: handlers/main.yml
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The tasks are individually broken out in 'acme/tasks/setup.yml', and handlers, which are common to all task files,
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are contained in 'acme/handlers/main.yml'. As a reminder, handlers are mostly just used to notify services to restart
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when things change, and these are described in :doc:`playbooks`.
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Including more than one setup file or more than one handlers file is of course legal.
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Bundling Ansible Modules With Playbooks
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+++++++++++++++++++++++++++++++++++++++
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.. versionadded:: 0.5
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If a playbook has a "./library" directory relative to it's YAML file,
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this directory can be used to add ansible modules that will
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automatically be in the ansible module path. This is a great way to
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keep modules that go with a playbook together.
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Miscellaneous Tips
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++++++++++++++++++
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When you can do something simply, do something simply. Do not reach
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to use every feature of Ansible together, all at once. Use what works
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for you. For example, you should probably not need 'vars',
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'vars_files', 'vars_prompt' and '--extra-vars' all at once,
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while also using an external inventory file.
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Optimize for readability. Whitespace between sections of YAML
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documents and in between tasks is strongly encouraged, as is usage of
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YAML comments, which start with '#'. It is also useful to comment
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at the top of each file the purpose of the individual file and the
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author, including email address.
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It is possible to leave off the 'name' for a given task, though it
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is recommended to provide a descriptive comment about why something is
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being done instead.
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Use version control. Keep your playbooks and inventory file in git
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(or another version control system), and commit when you make changes
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to them. This way you have an audit trail describing when and why you
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changed the rules automating your infrastructure.
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Resist the urge to write the same playbooks and configuration files
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for heterogeneous distributions. While lots of software packages
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claim to make this easy on you, the configuration files are often
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quite different, to the point where it would be easier to treat them
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as different playbooks. This is why, for example, Ansible has a
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separate :ref:`yum` and :ref:`apt` module. Yum and apt have different
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capabilities, and we don't want to code for the least common
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denominator.
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Use variables for user tunable settings versus having constants in the
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tasks file or templates, so that it is easy to reconfigure a playbook.
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Think about this as exposing the knobs to things you would like to
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tweak.
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Since a system can be in more than one group, if you have multiple
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datacenters or sites, consider putting systems into groups by role,
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but also different groups by geography. This allows you to assign
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different variables to different geographies.
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.. seealso::
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:doc:`YAMLSyntax`
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Learn about YAML syntax
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:doc:`playbooks`
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Review the basic playbook features
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:doc:`modules`
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Learn about available modules
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:doc:`moduledev`
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Learn how to extend Ansible by writing your own modules
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:doc:`patterns`
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Learn about how to select hosts
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`Github examples directory <https://github.com/ansible/ansible/tree/devel/examples/playbooks>`_
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Complete playbook files from the github project source
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`Mailing List <http://groups.google.com/group/ansible-project>`_
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Questions? Help? Ideas? Stop by the list on Google Groups
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