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<div class="section" id="playbooks">
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<h1>Playbooks<a class="headerlink" href="#playbooks" title="Permalink to this headline">¶</a></h1>
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<p>Playbooks are a completely different way to use ansible and are
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particularly awesome. They are the basis for a really simple
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configuration management and multi-machine deployment system,
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unlike any that already exist, and
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one that is very well suited to deploying complex applications.</p>
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<p>Playbooks can declare configurations, but they can also orchestrate steps of
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any manual ordered process, even as different steps must bounce back and forth
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between sets of machines in particular orders. They can launch tasks
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synchronously or asynchronously.</p>
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<p>While you might run the main /usr/bin/ansible program for ad-hoc
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tasks, playbooks are more likely to be kept in source control and used
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to push out your configuration or assure the configurations of your
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remote systems are in spec.</p>
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<p>Let’s dive in and see how they work. As you go, you may wish to open
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the <a class="reference external" href="https://github.com/ansible/ansible/tree/master/examples/playbooks">github examples directory</a> in
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another tab, so you can apply the theory to what things look like in practice.</p>
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<div class="section" id="playbook-example">
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<h2>Playbook Example<a class="headerlink" href="#playbook-example" title="Permalink to this headline">¶</a></h2>
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<p>Playbooks are expressed in YAML format and have a minimum of syntax.
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Each playbook is composed of one or more ‘plays’ in a list.</p>
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<p>By composing a playbook of multiple ‘plays’, it is possible to
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orchestrate multi-machine deployments, running certain steps on all
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machines in the webservers group, then certain steps on the database
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server group, then more commands back on the webservers group, etc.</p>
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<p>For starters, here’s a playbook that contains just one play.:</p>
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<div class="highlight-python"><pre>---
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- hosts: webservers
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vars:
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http_port: 80
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max_clients: 200
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user: root
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tasks:
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- name: ensure apache is at the latest version
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action: yum pkg=httpd state=latest
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- name: write the apache config file
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action: template src=/srv/httpd.j2 dest=/etc/httpd.conf
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notify:
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- restart apache
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- name: ensure apache is running
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action: service name=httpd state=started
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handlers:
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- name: restart apache
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action: service name=apache state=restarted</pre>
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</div>
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<p>Below, we’ll break down what the various features of the playbook language are.</p>
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</div>
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<div class="section" id="basics">
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<h2>Basics<a class="headerlink" href="#basics" title="Permalink to this headline">¶</a></h2>
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<div class="section" id="hosts-and-users">
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<h3>Hosts and Users<a class="headerlink" href="#hosts-and-users" title="Permalink to this headline">¶</a></h3>
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<p>For each play in a playbook, you get to choose which machines in your infrastructure
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to target and what remote user to complete the steps (called tasks) as.</p>
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<p>The <cite>hosts</cite> line is a list of one or more groups or host patterns,
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separated by colons, as described in the <a class="reference internal" href="patterns.html#patterns"><em>The Inventory File, Patterns, and Groups</em></a>
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documentation. The <cite>user</cite> is just the name of the user account:</p>
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<div class="highlight-python"><pre>---
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- hosts: webservers
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user: root</pre>
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</div>
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<p>Support for running things from sudo is also available:</p>
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<div class="highlight-python"><pre>---
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- hosts: webservers
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user: yourname
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sudo: True</pre>
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</div>
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</div>
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<div class="section" id="vars-section">
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<h3>Vars section<a class="headerlink" href="#vars-section" title="Permalink to this headline">¶</a></h3>
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<p>The <cite>vars</cite> section contains a list of variables and values that can be used in the plays, like this:</p>
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<div class="highlight-python"><pre>---
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- hosts: webservers
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users: root
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vars:
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http_port: 80
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van_halen_port: 5150
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other: 'magic'</pre>
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</div>
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<p>These variables can be used later in the playbook, or on the managed system (in templates), just like this:</p>
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<div class="highlight-python"><pre>{{ varname }}</pre>
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</div>
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<p>Within playbooks themselves, but not within templates on the remote machines, it’s also legal
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to use nicer shorthand like this:</p>
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<div class="highlight-python"><pre>$varname</pre>
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</div>
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<p>Further, if there are discovered variables about the system (say, if
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facter or ohai were installed) these variables bubble up back into the
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playbook, and can be used on each system just like explicitly set
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variables.</p>
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<p>Facter variables are prefixed with <tt class="docutils literal"><span class="pre">facter_</span></tt> and Ohai
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variables are prefixed with <tt class="docutils literal"><span class="pre">ohai_</span></tt>. So for instance, if I wanted
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to write the hostname into the /etc/motd file, I could say:</p>
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<div class="highlight-python"><pre>- name: write the motd
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action: template src=/srv/templates/motd.j2 dest=/etc/motd</pre>
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</div>
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<p>And in /srv/templates/motd.j2:</p>
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<div class="highlight-python"><pre>You are logged into {{ facter_hostname }}</pre>
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</div>
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<p>But we’re getting ahead of ourselves. Let’s talk about tasks.</p>
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</div>
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<div class="section" id="tasks-list">
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<h3>Tasks list<a class="headerlink" href="#tasks-list" title="Permalink to this headline">¶</a></h3>
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<p>Each play contains a list of tasks. Tasks are executed in order, one
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at a time, against all machines matched by the host pattern,
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before moving on to the next task.</p>
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<p>Hosts with failed tasks are taken out of the rotation for the entire
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playbook. If things fail, simply correct the playbook file and rerun.</p>
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<p>The goal of each task is to execute a module, with very specific arguments.
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Variables, as mentioned above, can be used in arguments to modules.</p>
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<p>Modules other than <cite>command</cite> are ‘idempotent’, meaning if you run them
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again, they will make the changes they are told to make to bring the
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system to the desired state. This makes it very safe to rerun
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the same playbook multiple times. They won’t change things
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unless they have to change things.</p>
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<p>Command will actually rerun the same command again,
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which is totally ok if the command is something like
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‘chmod’ or ‘setsebool’, etc.</p>
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<p>Every task must have a name, which is included in the output from
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running the playbook. This is output for humans, so it is
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nice to have reasonably good descriptions of each task step.</p>
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<p>Here is what a basic task looks like, as with most modules,
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the service module takes key=value arguments:</p>
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<div class="highlight-python"><pre>tasks:
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- name: make sure apache is running
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action: service name=httpd state=running</pre>
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</div>
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<p>The command module is the one module that just takes a list
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of arguments, and doesn’t use the key=value form. This makes
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it work just like you would expect. Simple:</p>
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<div class="highlight-python"><pre>tasks:
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- name: disable selinux
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action: command /sbin/setenforce 0</pre>
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</div>
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<p>Variables can be used in action lines. Suppose you defined
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a variable called ‘vhost’ in the ‘vars’ section, you could do this:</p>
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<div class="highlight-python"><pre>tasks:
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- name: make a directory
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action: template src=somefile.j2 dest=/etc/httpd/conf.d/$vhost</pre>
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</div>
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<p>Those same variables are usable in templates, which we’ll get to later.</p>
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</div>
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</div>
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<div class="section" id="running-operations-on-change">
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<h2>Running Operations On Change<a class="headerlink" href="#running-operations-on-change" title="Permalink to this headline">¶</a></h2>
|
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<p>As we’ve mentioned, nearly all modules are written to be ‘idempotent’ and can relay when
|
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they have affected a change on the remote system. Playbooks recognize this and
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have a basic event system that can be used to respond to change.</p>
|
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<p>These ‘notify’ actions are triggered at the end of each ‘play’ in a playbook, and
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trigger only once each. For instance, multiple resources may indicate
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that apache needs to be restarted, but apache will only be bounced once.</p>
|
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<p>Here’s an example of restarting two services when the contents of a file
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change, but only if the file changes:</p>
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<div class="highlight-python"><pre>- name: template configuration file
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action: template src=template.j2 dest=/etc/foo.conf
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notify:
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- restart memcached
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- restart apache</pre>
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</div>
|
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<p>The things listed in the ‘notify’ section of a task are called
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handlers.</p>
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<p>Handlers are lists of tasks, not really any different from regular
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tasks, that are referenced by name. Handlers are what notifiers
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notify. If nothing notifies a handler, it will not run. Regardless
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|
of how many things notify a handler, it will run only once, after all
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of the tasks complete in a particular play.</p>
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<p>Here’s an example handlers section:</p>
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<div class="highlight-python"><pre>handlers:
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- name: restart memcached
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action: service name=memcached state=restarted
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- name: restart apache
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action: service name=apache state=restarted</pre>
|
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</div>
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<p>Handlers are best used to restart services and trigger reboots. You probably
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won’t need them for much else.</p>
|
|
<div class="admonition note">
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<p class="first admonition-title">Note</p>
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<p class="last">Notify handlers are always run in the order written.</p>
|
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</div>
|
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</div>
|
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<div class="section" id="power-tricks">
|
|
<h2>Power Tricks<a class="headerlink" href="#power-tricks" title="Permalink to this headline">¶</a></h2>
|
|
<p>Now that you have the basics down, let’s learn some more advanced
|
|
things you can do with playbooks.</p>
|
|
<div class="section" id="external-variables-and-sensitive-data">
|
|
<h3>External Variables And Sensitive Data<a class="headerlink" href="#external-variables-and-sensitive-data" title="Permalink to this headline">¶</a></h3>
|
|
<p>It’s a great idea to keep your playbooks under source control, but
|
|
you may wish to make the playbook source public while keeping certain
|
|
important variables private. You can do this by using an external
|
|
variables file, or files, just like this:</p>
|
|
<div class="highlight-python"><pre>---
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|
- hosts: all
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|
user: root
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|
vars:
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|
favcolor: blue
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|
vars_files:
|
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- /vars/external_vars.yml
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tasks:
|
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- name: this is just a placeholder
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action: command /bin/echo foo</pre>
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</div>
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|
<p>This removes the risk of sharing sensitive data with others when
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sharing your playbook source with them.</p>
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|
<p>The contents of each variables file is a simple YAML dictionary, like this:</p>
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|
<div class="highlight-python"><pre>---
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|
# in the above example, this would be vars/external_vars.yml
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somevar: somevalue
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password: magic</pre>
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</div>
|
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</div>
|
|
<div class="section" id="conditional-execution">
|
|
<h3>Conditional Execution<a class="headerlink" href="#conditional-execution" title="Permalink to this headline">¶</a></h3>
|
|
<p>Sometimes you will want to skip a particular step on a particular host. This could be something
|
|
as simple as not installing a certain package if the operating system is a particular version,
|
|
or it could be something like performing some cleanup steps if a filesystem is getting full.</p>
|
|
<p>This is easy to do in Ansible, with the <cite>only_if</cite> clause. This clause can be applied to any task,
|
|
and allows usage of variables from anywhere in ansible, either denoted with <cite>$dollar_sign_syntax</cite> or
|
|
<cite>{{ braces_syntax }}</cite> and then evaluates them with a Python expression. Don’t panic – it’s actually
|
|
pretty simple.:</p>
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|
<div class="highlight-python"><pre>vars:
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|
favcolor: blue
|
|
is_favcolor_blue: "'$favcolor' == 'blue'"
|
|
is_centos: "'$facter_operatingsystem' == 'CentOS'"
|
|
tasks:
|
|
- name: "shutdown if my favorite color is blue"
|
|
action: command /sbin/shutdown -t now
|
|
only_if: '$is_favcolor_blue'</pre>
|
|
</div>
|
|
<p>Variables from tools like <cite>facter</cite> and <cite>ohai</cite> can be used here, if installed. As a reminder,
|
|
these variables are prefixed, so it’s <cite>$facter_operatingsystem</cite>, not <cite>$operatingsystem</cite>. The only_if
|
|
expression is actually a tiny small bit of Python, so be sure to quote variables and make something
|
|
that evaluates to <cite>True</cite> or <cite>False</cite>. It is a good idea to use ‘vars_files’ instead of ‘vars’ to define
|
|
all of your conditional expressions in a way that makes them very easy to reuse between plays
|
|
and playbooks.</p>
|
|
</div>
|
|
<div class="section" id="conditional-imports">
|
|
<h3>Conditional Imports<a class="headerlink" href="#conditional-imports" title="Permalink to this headline">¶</a></h3>
|
|
<p>Sometimes you will want to do certain things differently in a playbook based on certain criteria.
|
|
Having one playbook that works on multiple platforms and OS versions is a good example.</p>
|
|
<p>As an example, the name of the Apache package may be different between CentOS and Debian,
|
|
but it is easily handled with a minimum of syntax in an Ansible Playbook:</p>
|
|
<div class="highlight-python"><pre>---
|
|
- hosts: all
|
|
user: root
|
|
vars_files:
|
|
- "vars/common.yml"
|
|
- [ "vars/$facter_operatingsystem.yml", "vars/os_defaults.yml" ]
|
|
tasks:
|
|
- name: make sure apache is running
|
|
action: service name=$apache state=running</pre>
|
|
</div>
|
|
<p>As a reminder, the various YAML files contain just keys and values:</p>
|
|
<div class="highlight-python"><pre>---
|
|
# for vars/CentOS.yml
|
|
apache: httpd
|
|
somethingelse: 42</pre>
|
|
</div>
|
|
<p>How does this work? If the operating system was ‘CentOS’, the first file Ansible would try to import
|
|
would be ‘vars/CentOS.yml’, followed up by ‘/vars/os_defaults.yml’ if that file
|
|
did not exist. If no files in the list were found, an error would be raised.
|
|
On Debian, it would instead first look towards ‘vars/Debian.yml’ instead of ‘vars/CentOS.yml’, before
|
|
falling back on ‘vars/os_defaults.yml’. Pretty simple.</p>
|
|
<p>To use this conditional import feature, you’ll need facter or ohai installed prior to running the playbook, but
|
|
you can of course push this out with Ansible if you like:</p>
|
|
<div class="highlight-python"><pre># for facter
|
|
ansible -m yum -a "pkg=facter ensure=installed"
|
|
ansible -m yum -a "pkg=ruby-json ensure=installed"
|
|
|
|
# for ohai
|
|
ansible -m yum -a "pkg=ohai ensure=installed"</pre>
|
|
</div>
|
|
<p>Ansible’s approach to configuration – seperating variables from tasks, keeps your playbooks
|
|
from turning into arbitrary code with ugly nested ifs, conditionals, and so on - and results
|
|
in more streamlined & auditable configuration rules – especially because there are a
|
|
minimum of decision points to track.</p>
|
|
</div>
|
|
<div class="section" id="include-files-and-reuse">
|
|
<h3>Include Files And Reuse<a class="headerlink" href="#include-files-and-reuse" title="Permalink to this headline">¶</a></h3>
|
|
<p>Suppose you want to reuse lists of tasks between plays or playbooks. You can use
|
|
include files to do this.</p>
|
|
<p>An include file simply contains a flat list of tasks, like so:</p>
|
|
<div class="highlight-python"><pre>---
|
|
# possibly saved as tasks/foo.yml
|
|
- name: placeholder foo
|
|
action: command /bin/foo
|
|
- name: placeholder bar
|
|
action: command /bin/bar</pre>
|
|
</div>
|
|
<p>Include directives look like this:</p>
|
|
<div class="highlight-python"><pre>- tasks:
|
|
- include: tasks/foo.yml</pre>
|
|
</div>
|
|
<p>Variables passed in can be used in the include files too. Assume a variable named ‘user’. Using
|
|
<cite>jinja2</cite> syntax, anywhere in the included file, you can say:</p>
|
|
<div class="highlight-python"><pre>{{ user }}</pre>
|
|
</div>
|
|
<p>I can also pass variables into includes directly. We might call this a ‘parameterized include’.</p>
|
|
<p>For instance, if deploying multiple wordpress instances, I could
|
|
contain all of my wordpress tasks in a single wordpress.yml file, and use it like so:</p>
|
|
<div class="highlight-python"><pre>- tasks:
|
|
- include: wordpress.yml user=timmy
|
|
- include: wordpress.yml user=alice
|
|
- include: wordpress.yml user=bob</pre>
|
|
</div>
|
|
<p>In addition to the explicitly passed in parameters, all variables from
|
|
the vars section are also available for use here as well. Variables that bubble
|
|
up from tools like facter and ohai are not usable here though – but they ARE available for use
|
|
inside ‘action’ lines and in templates.</p>
|
|
<div class="admonition note">
|
|
<p class="first admonition-title">Note</p>
|
|
<p class="last">Include statements are only usable from the top level
|
|
playbook file. This means includes can not include other
|
|
includes.</p>
|
|
</div>
|
|
<p>Includes can also be used in the ‘handlers’ section, for instance, if you
|
|
want to define how to restart apache, you only have to do that once for all
|
|
of your playbooks. You might make a notifiers.yaml that looked like:</p>
|
|
<div class="highlight-python"><pre>----
|
|
# this might be in a file like handlers/handlers.yml
|
|
- name: restart apache
|
|
action: service name=apache state=restarted</pre>
|
|
</div>
|
|
<p>And in your main playbook file, just include it like so, at the bottom
|
|
of a play:</p>
|
|
<div class="highlight-python"><pre>handlers:
|
|
- include: handlers/handlers.yml</pre>
|
|
</div>
|
|
<p>You can mix in includes along with your regular non-included tasks and handlers.</p>
|
|
<p>Note that you can not conditionally path the location to an include file, like you can
|
|
with ‘vars_files’. If you find yourself needing to do this, consider how you can
|
|
restructure your playbook to be more class/role oriented.</p>
|
|
</div>
|
|
<div class="section" id="using-includes-to-assign-classes-of-systems">
|
|
<h3>Using Includes To Assign Classes of Systems<a class="headerlink" href="#using-includes-to-assign-classes-of-systems" title="Permalink to this headline">¶</a></h3>
|
|
<p>Include files are really powerful when used to reuse logic between playbooks. You
|
|
could imagine a playbook describing your entire infrastructure like
|
|
this, in a list of just a few plays:</p>
|
|
<div class="highlight-python"><pre>---
|
|
- hosts: atlanta-webservers
|
|
vars:
|
|
datacenter: atlanta
|
|
tasks:
|
|
- include: tasks/base.yml
|
|
- include: tasks/webservers.yml database=db.atlanta.com
|
|
handlers:
|
|
- include: handlers/common.yml
|
|
- hosts: atlanta-dbservers
|
|
vars:
|
|
datacenter: atlanta
|
|
tasks:
|
|
- include: tasks/base.yml
|
|
- include: tasks/dbservers.yml
|
|
handlers:
|
|
- include: handlers/common.yml</pre>
|
|
</div>
|
|
<p>There is one (or more) play defined for each group of systems, and
|
|
each play maps each group to several includes. These includes represent
|
|
‘class definitions’, telling the systems what they are supposed to do or be.
|
|
In the above example, all hosts get the base configuration first and further
|
|
customize it depending on what class or nature of machines they are.</p>
|
|
<div class="admonition note">
|
|
<p class="first admonition-title">Note</p>
|
|
<p class="last">Playbooks do not always have to be declarative; you can do something
|
|
similar to model a push process for a multi-tier web application. This is
|
|
actually one of the things playbooks were invented to do.</p>
|
|
</div>
|
|
</div>
|
|
<div class="section" id="asynchronous-actions-and-polling">
|
|
<h3>Asynchronous Actions and Polling<a class="headerlink" href="#asynchronous-actions-and-polling" title="Permalink to this headline">¶</a></h3>
|
|
<p>By default tasks in playbooks block, meaning the connections stay open
|
|
until the task is done on each node. If executing playbooks with
|
|
a small parallelism value (aka <cite>–forks</cite>), you may wish that long
|
|
running operations can go faster. The easiest way to do this is
|
|
to kick them off all at once and then poll until they are done.</p>
|
|
<p>You will also want to use asynchronous mode on very long running
|
|
operations that might be subject to timeout.</p>
|
|
<p>To launch a task asynchronously, specify it’s maximum runtime
|
|
and how frequently you would like to poll for status. The default
|
|
poll value is 10 seconds if you do not specify a value for <cite>poll</cite>:</p>
|
|
<div class="highlight-python"><pre>---
|
|
- hosts: all
|
|
user: root
|
|
tasks:
|
|
- name: simulate long running op (15 sec), wait for up to 45, poll every 5
|
|
action: command /bin/sleep 15
|
|
async: 45
|
|
poll: 5</pre>
|
|
</div>
|
|
<div class="admonition note">
|
|
<p class="first admonition-title">Note</p>
|
|
<p class="last">There is no default for the async time limit. If you leave off the
|
|
‘async’ keyword, the task runs synchronously, which is Ansible’s
|
|
default.</p>
|
|
</div>
|
|
<p>Alternatively, if you do not need to wait on the task to complete, you may
|
|
“fire and forget” by specifying a poll value of 0:</p>
|
|
<div class="highlight-python"><pre>---
|
|
- hosts: all
|
|
user: root
|
|
tasks:
|
|
- name: simulate long running op, allow to run for 45, fire and forget
|
|
action: command /bin/sleep 15
|
|
async: 45
|
|
poll: 0</pre>
|
|
</div>
|
|
<div class="admonition note">
|
|
<p class="first admonition-title">Note</p>
|
|
<p class="last">You shouldn’t “fire and forget” with operations that require
|
|
exclusive locks, such as yum transactions, if you expect to run other
|
|
commands later in the playbook against those same resources.</p>
|
|
</div>
|
|
<div class="admonition note">
|
|
<p class="first admonition-title">Note</p>
|
|
<p class="last">Using a higher value for <cite>–forks</cite> will result in kicking off asynchronous
|
|
tasks even faster. This also increases the efficiency of polling.</p>
|
|
</div>
|
|
</div>
|
|
</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>Now that you’ve learned playbook syntax, how do you run a playbook? It’s simple.
|
|
Let’s run a playbook using a parallelism level of 10:</p>
|
|
<div class="highlight-python"><pre>ansible-playbook playbook.yml -f 10</pre>
|
|
</div>
|
|
<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="YAMLSyntax.html"><em>YAML Syntax</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</dd>
|
|
<dt><a class="reference internal" href="moduledev.html"><em>Module Development Guide</em></a></dt>
|
|
<dd>Learn how to extend Ansible by writing your own modules</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>
|
|
<dt><a class="reference external" href="https://github.com/ansible/ansible/tree/master/examples/playbooks">Github examples directory</a></dt>
|
|
<dd>Complete playbook files from the github project source</dd>
|
|
<dt><a class="reference external" href="http://groups.google.com/group/ansible-project">Mailing List</a></dt>
|
|
<dd>Questions? Help? Ideas? Stop by the list on Google Groups</dd>
|
|
</dl>
|
|
</div>
|
|
</div>
|
|
</div>
|
|
|
|
|
|
</div>
|
|
<footer class="footer">
|
|
<div class="container">
|
|
<p class="pull-right"><a href="#">Back to top</a></p>
|
|
<p>
|
|
© Copyright 2012 Michael DeHaan.<br/>
|
|
Last updated on Mar 31, 2012.<br/>
|
|
Created using <a href="http://sphinx.pocoo.org/">Sphinx</a> 1.0.8.<br/>
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</p>
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