ansible/html/playbooks.html
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<div class="section" id="playbooks-ansible-for-deployment-configuration-management-and-orchestration">
<h1>Playbooks: Ansible for Deployment, Configuration Management, and Orchestration<a class="headerlink" href="#playbooks-ansible-for-deployment-configuration-management-and-orchestration" title="Permalink to this headline"></a></h1>
<div class="admonition-see-also admonition seealso">
<p class="first admonition-title">See also</p>
<dl class="last docutils">
<dt><a class="reference internal" href="YAMLScripts.html"><em>YAML Scripts</em></a></dt>
<dd>Learn about YAML syntax</dd>
<dt><a class="reference internal" href="modules.html"><em>Ansible Modules</em></a></dt>
<dd>Learn about available modules and writing your own</dd>
<dt><a class="reference internal" href="patterns.html"><em>The Inventory File, Patterns, and Groups</em></a></dt>
<dd>Learn about how to select hosts</dd>
</dl>
</div>
<p>Playbooks are a completely different way to use ansible and are particularly awesome. They are the basis for a really simple configuration management and deployment system, unlike any that already exist, and one that is very well suited to deploying complex multi-machine applications. While you might run the main ansible program for ad-hoc tasks, playbooks are more likely to be kept in source control and used to push out your configuration or assure the configurations of your remote systems are in spec.</p>
<div class="section" id="playbook-example">
<h2>Playbook Example<a class="headerlink" href="#playbook-example" title="Permalink to this headline"></a></h2>
<p>Playbooks are expressed in YAML format and have a minimum of syntax. Each playbook is composed
of one or more &#8216;plays&#8217; in a list. By composing a playbook of multiple &#8216;plays&#8217;, it is possible
to orchestrate multi-machine deployments, running certain steps on all machines in
the webservers group, then certain steps on the database server group, then more commands
back on the webservers group, etc:</p>
<div class="highlight-python"><pre>---
- hosts: webservers
vars:
http_port: 80
max_clients: 200
user: root
tasks:
- include: base.yml somevar=3 othervar=4
- name: write the apache config file
action: template src=/srv/httpd.j2 dest=/etc/httpd.conf
notify:
- restart apache
- name: ensure apache is running
action: service name=httpd state=started
handlers:
- include: handlers.yml</pre>
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<div class="section" id="hosts-line">
<h2>Hosts line<a class="headerlink" href="#hosts-line" title="Permalink to this headline"></a></h2>
<p>The hosts line is alist of one or more groups or host patterns, seperated by colons, as
described in the &#8216;patterns&#8217; documentation.</p>
</div>
<div class="section" id="vars-section">
<h2>Vars section<a class="headerlink" href="#vars-section" title="Permalink to this headline"></a></h2>
<p>A list of variables that can be used in the templates, action lines, or included files.
Variables are deferenced using <tt class="docutils literal"><span class="pre">jinja2</span></tt> syntax like this:</p>
<div class="highlight-python"><pre>{{ varname }}</pre>
</div>
<p>These variables will be pushed down to the managed systems for use in templating operations, where
the way to dereference them in templates is exactly the same.</p>
<p>Further, if there are discovered variables about the system (say, if facter or ohai were
installed) these variables bubble up back into the playbook, and can be used on each
system just like explicitly set variables. Facter variables are prefixed with &#8216;<a href="#id1"><span class="problematic" id="id2">facter_</span></a>&#8216;
and Ohai variables are prefixed with &#8216;<a href="#id3"><span class="problematic" id="id4">ohai_</span></a>&#8216;.</p>
</div>
<div class="section" id="tasks-list">
<h2>Tasks list<a class="headerlink" href="#tasks-list" title="Permalink to this headline"></a></h2>
<p>Each play contains a list of tasks. Tasks are executed in order, one at a time, against
all machines matched by the play&#8217;s host pattern, before moving on to the next task.
Hosts with failed tasks are taken out of the rotation for the entire playbook. If things fail,
correct the problem and rerun. Modules other than command are idempotent, meaning if you
run them again, they will make the changes they are told to make to bring the system to
the desired state.</p>
</div>
<div class="section" id="task-name-and-action">
<h2>Task name and action<a class="headerlink" href="#task-name-and-action" title="Permalink to this headline"></a></h2>
<p>Every task must have a name, which is included in the output from running the playbook.</p>
<p>The action line is the name of an ansible module followed by parameters. Usually these
are expressed in key=value form, except for the command module, which looks just like a Linux/Unix
command line. See the module documentation for more info.</p>
</div>
<div class="section" id="notify-statements">
<h2>Notify statements<a class="headerlink" href="#notify-statements" title="Permalink to this headline"></a></h2>
<p>Nearly all modules are written to be &#8216;idempotent&#8217; and can signal when they have affected a change
on the remote system. If a notify statement is used, the named handler will be run against
each system where a change was effected, but NOT on systems where no change occurred.</p>
</div>
<div class="section" id="handlers">
<h2>Handlers<a class="headerlink" href="#handlers" title="Permalink to this headline"></a></h2>
<p>Handlers are lists of tasks, not really any different from regular tasks, that are referenced
by name.</p>
</div>
<div class="section" id="includes">
<h2>Includes<a class="headerlink" href="#includes" title="Permalink to this headline"></a></h2>
<p>Not all tasks have to be listed directly in the main file. An include file can contain
a list of tasks (in YAML) as well, optionally passing extra variables into the file.
Variables passed in can be deferenced like this:</p>
<blockquote>
<div>{{ variable }}</div></blockquote>
</div>
<div class="section" id="asynchronous-actions-and-polling">
<h2>Asynchronous Actions and Polling<a class="headerlink" href="#asynchronous-actions-and-polling" title="Permalink to this headline"></a></h2>
<p>(Information on this feature is pending)</p>
</div>
<div class="section" id="executing-a-playbook">
<h2>Executing A Playbook<a class="headerlink" href="#executing-a-playbook" title="Permalink to this headline"></a></h2>
<p>To run a playbook:</p>
<div class="highlight-python"><pre>ansible-playbook playbook.yml</pre>
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<h3><a href="index.html">Table Of Contents</a></h3>
<ul>
<li><a class="reference internal" href="#">Playbooks: Ansible for Deployment, Configuration Management, and Orchestration</a><ul>
<li><a class="reference internal" href="#playbook-example">Playbook Example</a></li>
<li><a class="reference internal" href="#hosts-line">Hosts line</a></li>
<li><a class="reference internal" href="#vars-section">Vars section</a></li>
<li><a class="reference internal" href="#tasks-list">Tasks list</a></li>
<li><a class="reference internal" href="#task-name-and-action">Task name and action</a></li>
<li><a class="reference internal" href="#notify-statements">Notify statements</a></li>
<li><a class="reference internal" href="#handlers">Handlers</a></li>
<li><a class="reference internal" href="#includes">Includes</a></li>
<li><a class="reference internal" href="#asynchronous-actions-and-polling">Asynchronous Actions and Polling</a></li>
<li><a class="reference internal" href="#executing-a-playbook">Executing A Playbook</a></li>
</ul>
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&copy; Copyright 2012 Michael DeHaan.
Last updated on Mar 08, 2012.
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