441 lines
15 KiB
ReStructuredText
441 lines
15 KiB
ReStructuredText
Intro to Playbooks
|
|
==================
|
|
|
|
.. _about_playbooks:
|
|
|
|
About Playbooks
|
|
```````````````
|
|
|
|
Playbooks are a completely different way to use ansible than in adhoc task execution mode, and are
|
|
particularly powerful.
|
|
|
|
Simply put, playbooks are the basis for a really simple configuration management and multi-machine deployment system,
|
|
unlike any that already exist, and one that is very well suited to deploying complex applications.
|
|
|
|
Playbooks can declare configurations, but they can also orchestrate steps of
|
|
any manual ordered process, even as different steps must bounce back and forth
|
|
between sets of machines in particular orders. They can launch tasks
|
|
synchronously or asynchronously.
|
|
|
|
While you might run the main /usr/bin/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.
|
|
|
|
There are also some full sets of playbooks illustrating a lot of these techniques in the
|
|
`ansible-examples repository <https://github.com/ansible/ansible-examples>`_. We'd recommend
|
|
looking at these in another tab as you go along.
|
|
|
|
There are also many jumping off points after you learn playbooks, so hop back to the documentation
|
|
index after you're done with this section.
|
|
|
|
.. _playbook_language_example:
|
|
|
|
Playbook Language Example
|
|
`````````````````````````
|
|
|
|
Playbooks are expressed in YAML format (see :doc:`YAMLSyntax`) and have a minimum of syntax, which intentionally
|
|
tries to not be a programming language or script, but rather a model of a configuration or a process.
|
|
|
|
Each playbook is composed of one or more 'plays' in a list.
|
|
|
|
The goal of a play is to map a group of hosts to some well defined roles, represented by
|
|
things ansible calls tasks. At a basic level, a task is nothing more than a call
|
|
to an ansible module, which you should have learned about in earlier chapters.
|
|
|
|
By composing a playbook of multiple 'plays', 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.
|
|
|
|
"plays" are more or less a sports analogy. You can have quite a lot of plays that affect your systems
|
|
to do different things. It's not as if you were just defining one particular state or model, and you
|
|
can run different plays at different times.
|
|
|
|
For starters, here's a playbook that contains just one play::
|
|
|
|
---
|
|
- hosts: webservers
|
|
vars:
|
|
http_port: 80
|
|
max_clients: 200
|
|
remote_user: root
|
|
tasks:
|
|
- name: ensure apache is at the latest version
|
|
yum: pkg=httpd state=latest
|
|
- name: write the apache config file
|
|
template: src=/srv/httpd.j2 dest=/etc/httpd.conf
|
|
notify:
|
|
- restart apache
|
|
- name: ensure apache is running (and enable it at boot)
|
|
service: name=httpd state=started enabled=yes
|
|
handlers:
|
|
- name: restart apache
|
|
service: name=httpd state=restarted
|
|
|
|
We can also break task items out over multiple lines using the YAML dictionary
|
|
types to supply module arguments. This can be helpful when working with tasks
|
|
that have really long parameters or modules that take many parameters to keep
|
|
them well structured. Below is another version of the above example but using
|
|
YAML dictionaries to supply the modules with their key=value arguments.::
|
|
|
|
---
|
|
- hosts: webservers
|
|
vars:
|
|
http_port: 80
|
|
max_clients: 200
|
|
remote_user: root
|
|
tasks:
|
|
- name: ensure apache is at the latest version
|
|
yum:
|
|
pkg: httpd
|
|
state: latest
|
|
- name: write the apache config file
|
|
template:
|
|
src: /srv/httpd.j2
|
|
dest: /etc/httpd.conf
|
|
notify:
|
|
- restart apache
|
|
- name: ensure apache is running
|
|
service:
|
|
name: httpd
|
|
state: started
|
|
handlers:
|
|
- name: restart apache
|
|
service:
|
|
name: httpd
|
|
state: restarted
|
|
|
|
Below, we'll break down what the various features of the playbook language are.
|
|
|
|
.. _playbook_basics:
|
|
|
|
Basics
|
|
``````
|
|
|
|
.. _playbook_hosts_and_users:
|
|
|
|
Hosts and Users
|
|
+++++++++++++++
|
|
|
|
For each play in a playbook, you get to choose which machines in your infrastructure
|
|
to target and what remote user to complete the steps (called tasks) as.
|
|
|
|
The `hosts` line is a list of one or more groups or host patterns,
|
|
separated by colons, as described in the :doc:`intro_patterns`
|
|
documentation. The `remote_user` is just the name of the user account::
|
|
|
|
---
|
|
- hosts: webservers
|
|
remote_user: root
|
|
|
|
.. note::
|
|
|
|
The `remote_user` parameter was formerly called just `user`. It was renamed in Ansible 1.4 to make it more distinguishable from the `user` module (used to create users on remote systems).
|
|
|
|
Remote users can also be defined per task::
|
|
|
|
---
|
|
- hosts: webservers
|
|
remote_user: root
|
|
tasks:
|
|
- name: test connection
|
|
ping:
|
|
remote_user: yourname
|
|
|
|
.. note::
|
|
|
|
The `remote_user` parameter for tasks was added in 1.4.
|
|
|
|
|
|
Support for running things as another user is also available (see :doc:`become`)::
|
|
|
|
---
|
|
- hosts: webservers
|
|
remote_user: yourname
|
|
sudo: yes
|
|
|
|
You can also use sudo on a particular task instead of the whole play::
|
|
|
|
---
|
|
- hosts: webservers
|
|
remote_user: yourname
|
|
tasks:
|
|
- service: name=nginx state=started
|
|
become: yes
|
|
become_method: sudo
|
|
|
|
.. note::
|
|
|
|
The become syntax deprecates the old sudo/su specific syntax beginning in 1.9.
|
|
|
|
You can also login as you, and then become a user different than root::
|
|
|
|
---
|
|
- hosts: webservers
|
|
remote_user: yourname
|
|
become: yes
|
|
become_user: postgres
|
|
|
|
You can also use other privilege escalation methods, like su::
|
|
|
|
---
|
|
- hosts: webservers
|
|
remote_user: yourname
|
|
become: yes
|
|
become_method: su
|
|
|
|
If you need to specify a password to sudo, run `ansible-playbook` with ``--ask-become-pass`` or
|
|
when using the old sudo syntax ``--ask-sudo--pass`` (`-K`). If you run a become playbook and the
|
|
playbook seems to hang, it's probably stuck at the privilege escalation prompt.
|
|
Just `Control-C` to kill it and run it again adding the appropriate password.
|
|
|
|
.. important::
|
|
|
|
When using `become_user` to a user other than root, the module
|
|
arguments are briefly written into a random tempfile in /tmp.
|
|
These are deleted immediately after the command is executed. This
|
|
only occurs when changing privileges from a user like 'bob' to 'timmy',
|
|
not when going from 'bob' to 'root', or logging in directly as 'bob' or
|
|
'root'. If it concerns you that this data is briefly readable
|
|
(not writable), avoid transferring unencrypted passwords with
|
|
`become_user` set. In other cases, '/tmp' is not used and this does
|
|
not come into play. Ansible also takes care to not log password
|
|
parameters.
|
|
|
|
.. _tasks_list:
|
|
|
|
Tasks list
|
|
++++++++++
|
|
|
|
Each play contains a list of tasks. Tasks are executed in order, one
|
|
at a time, against all machines matched by the host pattern,
|
|
before moving on to the next task. It is important to understand that, within a play,
|
|
all hosts are going to get the same task directives. It is the purpose of a play to map
|
|
a selection of hosts to tasks.
|
|
|
|
When running the playbook, which runs top to bottom, hosts with failed tasks are
|
|
taken out of the rotation for the entire playbook. If things fail, simply correct the playbook file and rerun.
|
|
|
|
The goal of each task is to execute a module, with very specific arguments.
|
|
Variables, as mentioned above, can be used in arguments to modules.
|
|
|
|
Modules are 'idempotent', meaning if you run them
|
|
again, they will make only the changes they must in order to bring the
|
|
system to the desired state. This makes it very safe to rerun
|
|
the same playbook multiple times. They won't change things
|
|
unless they have to change things.
|
|
|
|
The `command` and `shell` modules will typically rerun the same command again,
|
|
which is totally ok if the command is something like
|
|
'chmod' or 'setsebool', etc. Though there is a 'creates' flag available which can
|
|
be used to make these modules also idempotent.
|
|
|
|
Every task should have a `name`, which is included in the output from
|
|
running the playbook. This is output for humans, so it is
|
|
nice to have reasonably good descriptions of each task step. If the name
|
|
is not provided though, the string fed to 'action' will be used for
|
|
output.
|
|
|
|
Tasks can be declared using the legacy "action: module options" format, but
|
|
it is recommended that you use the more conventional "module: options" format.
|
|
This recommended format is used throughout the documentation, but you may
|
|
encounter the older format in some playbooks.
|
|
|
|
Here is what a basic task looks like. As with most modules,
|
|
the service module takes key=value arguments::
|
|
|
|
tasks:
|
|
- name: make sure apache is running
|
|
service: name=httpd state=running
|
|
|
|
The `command` and `shell` modules are the only modules that just take a list
|
|
of arguments and don't use the key=value form. This makes
|
|
them work as simply as you would expect::
|
|
|
|
tasks:
|
|
- name: disable selinux
|
|
command: /sbin/setenforce 0
|
|
|
|
The command and shell module care about return codes, so if you have a command
|
|
whose successful exit code is not zero, you may wish to do this::
|
|
|
|
tasks:
|
|
- name: run this command and ignore the result
|
|
shell: /usr/bin/somecommand || /bin/true
|
|
|
|
Or this::
|
|
|
|
tasks:
|
|
- name: run this command and ignore the result
|
|
shell: /usr/bin/somecommand
|
|
ignore_errors: True
|
|
|
|
|
|
If the action line is getting too long for comfort you can break it on
|
|
a space and indent any continuation lines::
|
|
|
|
tasks:
|
|
- name: Copy ansible inventory file to client
|
|
copy: src=/etc/ansible/hosts dest=/etc/ansible/hosts
|
|
owner=root group=root mode=0644
|
|
|
|
Variables can be used in action lines. Suppose you defined
|
|
a variable called 'vhost' in the 'vars' section, you could do this::
|
|
|
|
tasks:
|
|
- name: create a virtual host file for {{ vhost }}
|
|
template: src=somefile.j2 dest=/etc/httpd/conf.d/{{ vhost }}
|
|
|
|
Those same variables are usable in templates, which we'll get to later.
|
|
|
|
Now in a very basic playbook all the tasks will be listed directly in that play, though it will usually
|
|
make more sense to break up tasks using the 'include:' directive. We'll show that a bit later.
|
|
|
|
.. _action_shorthand:
|
|
|
|
Action Shorthand
|
|
````````````````
|
|
|
|
.. versionadded:: 0.8
|
|
|
|
Ansible prefers listing modules like this in 0.8 and later::
|
|
|
|
template: src=templates/foo.j2 dest=/etc/foo.conf
|
|
|
|
You will notice in earlier versions, this was only available as::
|
|
|
|
action: template src=templates/foo.j2 dest=/etc/foo.conf
|
|
|
|
The old form continues to work in newer versions without any plan of deprecation.
|
|
|
|
.. _handlers:
|
|
|
|
Handlers: Running Operations On Change
|
|
``````````````````````````````````````
|
|
|
|
As we've mentioned, modules are written to be 'idempotent' and can relay when
|
|
they have made a change on the remote system. Playbooks recognize this and
|
|
have a basic event system that can be used to respond to change.
|
|
|
|
These 'notify' actions are triggered at the end of each block of tasks in a playbook, and will only be
|
|
triggered once even if notified by multiple different tasks.
|
|
|
|
For instance, multiple resources may indicate
|
|
that apache needs to be restarted because they have changed a config file,
|
|
but apache will only be bounced once to avoid unnecessary restarts.
|
|
|
|
Here's an example of restarting two services when the contents of a file
|
|
change, but only if the file changes::
|
|
|
|
- name: template configuration file
|
|
template: src=template.j2 dest=/etc/foo.conf
|
|
notify:
|
|
- restart memcached
|
|
- restart apache
|
|
|
|
The things listed in the 'notify' section of a task are called
|
|
handlers.
|
|
|
|
Handlers are lists of tasks, not really any different from regular
|
|
tasks, that are referenced by name. Handlers are what notifiers
|
|
notify. If nothing notifies a handler, it will not run. Regardless
|
|
of how many things notify a handler, it will run only once, after all
|
|
of the tasks complete in a particular play.
|
|
|
|
Here's an example handlers section::
|
|
|
|
handlers:
|
|
- name: restart memcached
|
|
service: name=memcached state=restarted
|
|
- name: restart apache
|
|
service: name=apache state=restarted
|
|
|
|
Handlers are best used to restart services and trigger reboots. You probably
|
|
won't need them for much else.
|
|
|
|
.. note::
|
|
Notify handlers are always run in the order written.
|
|
|
|
Roles are described later on. It's worthwhile to point out that handlers are
|
|
automatically processed between 'pre_tasks', 'roles', 'tasks', and 'post_tasks'
|
|
sections. If you ever want to flush all the handler commands immediately though,
|
|
in 1.2 and later, you can::
|
|
|
|
tasks:
|
|
- shell: some tasks go here
|
|
- meta: flush_handlers
|
|
- shell: some other tasks
|
|
|
|
In the above example any queued up handlers would be processed early when the 'meta'
|
|
statement was reached. This is a bit of a niche case but can come in handy from
|
|
time to time.
|
|
|
|
.. _executing_a_playbook:
|
|
|
|
Executing A Playbook
|
|
````````````````````
|
|
|
|
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::
|
|
|
|
ansible-playbook playbook.yml -f 10
|
|
|
|
.. _ansible-pull:
|
|
|
|
Ansible-Pull
|
|
````````````
|
|
|
|
Should you want to invert the architecture of Ansible, so that nodes check in to a central location, instead
|
|
of pushing configuration out to them, you can.
|
|
|
|
Ansible-pull is a small script that will checkout a repo of configuration instructions from git, and then
|
|
run ansible-playbook against that content.
|
|
|
|
Assuming you load balance your checkout location, ansible-pull scales essentially infinitely.
|
|
|
|
Run ``ansible-pull --help`` for details.
|
|
|
|
There's also a `clever playbook <https://github.com/ansible/ansible-examples/blob/master/language_features/ansible_pull.yml>`_ available to configure ansible-pull via a crontab from push mode.
|
|
|
|
.. _tips_and_tricks:
|
|
|
|
Tips and Tricks
|
|
```````````````
|
|
|
|
Look at the bottom of the playbook execution for a summary of the nodes that were targeted
|
|
and how they performed. General failures and fatal "unreachable" communication attempts are
|
|
kept separate in the counts.
|
|
|
|
If you ever want to see detailed output from successful modules as well as unsuccessful ones,
|
|
use the ``--verbose`` flag. This is available in Ansible 0.5 and later.
|
|
|
|
Ansible playbook output is vastly upgraded if the cowsay
|
|
package is installed. Try it!
|
|
|
|
To see what hosts would be affected by a playbook before you run it, you
|
|
can do this::
|
|
|
|
ansible-playbook playbook.yml --list-hosts
|
|
|
|
.. seealso::
|
|
|
|
:doc:`YAMLSyntax`
|
|
Learn about YAML syntax
|
|
:doc:`playbooks_best_practices`
|
|
Various tips about managing playbooks in the real world
|
|
:doc:`index`
|
|
Hop back to the documentation index for a lot of special topics about playbooks
|
|
:doc:`modules`
|
|
Learn about available modules
|
|
:doc:`developing_modules`
|
|
Learn how to extend Ansible by writing your own modules
|
|
:doc:`intro_patterns`
|
|
Learn about how to select hosts
|
|
`Github examples directory <https://github.com/ansible/ansible-examples>`_
|
|
Complete end-to-end playbook examples
|
|
`Mailing List <http://groups.google.com/group/ansible-project>`_
|
|
Questions? Help? Ideas? Stop by the list on Google Groups
|
|
|
|
|
|
|