mirror of https://github.com/ansible/ansible.git
Update tags and async sections, among other changes.
Michael DeHaan
11 years ago
parent
c10904bcef
commit
ad2736b253
File diff suppressed because it is too large
Load Diff
@ -1,397 +0,0 @@
|
||||
API & Integrations
|
||||
==================
|
||||
|
||||
There are several interesting ways to use Ansible from an API perspective. You can use
|
||||
the Ansible python API to control nodes, you can extend Ansible to respond to various python events,
|
||||
and you can plug in inventory data from external data sources. Ansible is written in its own
|
||||
API so you have a considerable amount of power across the board.
|
||||
|
||||
.. contents:: `Table of contents`
|
||||
:depth: 2
|
||||
|
||||
Python API
|
||||
----------
|
||||
|
||||
The Python API is very powerful, and is how the ansible CLI and ansible-playbook
|
||||
are implemented.
|
||||
|
||||
It's pretty simple::
|
||||
|
||||
import ansible.runner
|
||||
|
||||
runner = ansible.runner.Runner(
|
||||
module_name='ping',
|
||||
module_args='',
|
||||
pattern='web*',
|
||||
forks=10
|
||||
)
|
||||
datastructure = runner.run()
|
||||
|
||||
The run method returns results per host, grouped by whether they
|
||||
could be contacted or not. Return types are module specific, as
|
||||
expressed in the 'ansible-modules' documentation.::
|
||||
|
||||
{
|
||||
"dark" : {
|
||||
"web1.example.com" : "failure message"
|
||||
},
|
||||
"contacted" : {
|
||||
"web2.example.com" : 1
|
||||
}
|
||||
}
|
||||
|
||||
A module can return any type of JSON data it wants, so Ansible can
|
||||
be used as a framework to rapidly build powerful applications and scripts.
|
||||
|
||||
Detailed API Example
|
||||
````````````````````
|
||||
|
||||
The following script prints out the uptime information for all hosts::
|
||||
|
||||
#!/usr/bin/python
|
||||
|
||||
import ansible.runner
|
||||
import sys
|
||||
|
||||
# construct the ansible runner and execute on all hosts
|
||||
results = ansible.runner.Runner(
|
||||
pattern='*', forks=10,
|
||||
module_name='command', module_args='/usr/bin/uptime',
|
||||
).run()
|
||||
|
||||
if results is None:
|
||||
print "No hosts found"
|
||||
sys.exit(1)
|
||||
|
||||
print "UP ***********"
|
||||
for (hostname, result) in results['contacted'].items():
|
||||
if not 'failed' in result:
|
||||
print "%s >>> %s" % (hostname, result['stdout'])
|
||||
|
||||
print "FAILED *******"
|
||||
for (hostname, result) in results['contacted'].items():
|
||||
if 'failed' in result:
|
||||
print "%s >>> %s" % (hostname, result['msg'])
|
||||
|
||||
print "DOWN *********"
|
||||
for (hostname, result) in results['dark'].items():
|
||||
print "%s >>> %s" % (hostname, result)
|
||||
|
||||
Advanced programmers may also wish to read the source to ansible itself, for
|
||||
it uses the Runner() API (with all available options) to implement the
|
||||
command line tools ``ansible`` and ``ansible-playbook``.
|
||||
|
||||
Plugins Available Online
|
||||
------------------------
|
||||
|
||||
The remainder of features in the API docs have components available in `ansible-plugins <https://github.com/ansible/ansible/blob/devel/plugins>`_. Send us a github pull request if you develop any interesting features.
|
||||
|
||||
External Inventory Scripts
|
||||
--------------------------
|
||||
|
||||
Often a user of a configuration management system will want to keep inventory
|
||||
in a different system. Frequent examples include LDAP, `Cobbler <http://cobbler.github.com>`_,
|
||||
or a piece of expensive enterprisey CMDB software. Ansible easily supports all
|
||||
of these options via an external inventory system. The plugins directory contains some of these already -- including options for EC2/Eucalyptus and OpenStack, which will be detailed below.
|
||||
|
||||
It's possible to write an external inventory script in any language. If you are familiar with Puppet terminology, this concept is basically the same as 'external nodes', with the slight difference that it also defines which hosts are managed.
|
||||
|
||||
Script Conventions
|
||||
``````````````````
|
||||
|
||||
When the external node script is called with the single argument '--list', the script must return a JSON hash/dictionary of all the groups to be managed.
|
||||
Each group's value should be either a hash/dictionary containing a list of each host/IP, potential child groups, and potential group variables, or
|
||||
simply a list of host/IP addresses, like so::
|
||||
|
||||
{
|
||||
"databases" : {
|
||||
"hosts" : [ "host1.example.com", "host2.example.com" ],
|
||||
"vars" : {
|
||||
"a" : true
|
||||
}
|
||||
},
|
||||
"webservers" : [ "host2.example.com", "host3.example.com" ],
|
||||
"atlanta" : {
|
||||
"hosts" : [ "host1.example.com", "host4.example.com", "host5.example.com" ],
|
||||
"vars" : {
|
||||
"b" : false
|
||||
},
|
||||
"children": [ "marietta", "5points" ],
|
||||
},
|
||||
"marietta" : [ "host6.example.com" ],
|
||||
"5points" : [ "host7.example.com" ]
|
||||
}
|
||||
|
||||
.. versionadded:: 1.0
|
||||
|
||||
Before version 1.0, each group could only have a list of hostnames/IP addresses, like the webservers, marietta, and 5points groups above.
|
||||
|
||||
When called with the arguments '--host <hostname>' (where <hostname> is a host from above), the script must return either an empty JSON
|
||||
hash/dictionary, or a hash/dictionary of variables to make available to templates and playbooks. Returning variables is optional,
|
||||
if the script does not wish to do this, returning an empty hash/dictionary is the way to go::
|
||||
|
||||
{
|
||||
"favcolor" : "red",
|
||||
"ntpserver" : "wolf.example.com",
|
||||
"monitoring" : "pack.example.com"
|
||||
}
|
||||
|
||||
Tuning the External Inventory Script
|
||||
````````````````````````````````````
|
||||
|
||||
.. versionadded:: 1.3
|
||||
|
||||
The stock inventory script system detailed above works for all versions of Ansible, but calling
|
||||
'--host' for every host can be rather expensive, especially if it involves expensive API calls to
|
||||
a remote subsystemm. In Ansible
|
||||
1.3 or later, if the inventory script returns a top level element called "_meta", it is possible
|
||||
to return all of the host variables in one inventory script call. When this meta element contains
|
||||
a value for "hostvars", the inventory script will not be invoked with "--host" for each host. This
|
||||
results in a significant performance increase for large numbers of hosts, and also makes client
|
||||
side caching easier to implement for the inventory script.
|
||||
|
||||
The data to be added to the top level JSON dictionary looks like this::
|
||||
|
||||
{
|
||||
|
||||
# results of inventory script as above go here
|
||||
# ...
|
||||
|
||||
"_meta" : {
|
||||
"hostvars" : {
|
||||
"moocow.example.com" : { "asdf" : 1234 },
|
||||
"llama.example.com" : { "asdf" : 5678 },
|
||||
}
|
||||
}
|
||||
|
||||
}
|
||||
|
||||
|
||||
Example: The Cobbler External Inventory Script
|
||||
``````````````````````````````````````````````
|
||||
|
||||
It is expected that many Ansible users will also be `Cobbler <http://cobbler.github.com>`_ users. Cobbler has a generic
|
||||
layer that allows it to represent data for multiple configuration management systems (even at the same time), and has
|
||||
been referred to as a 'lightweight CMDB' by some admins. This particular script will communicate with Cobbler
|
||||
using Cobbler's XMLRPC API.
|
||||
|
||||
To tie Ansible's inventory to Cobbler (optional), copy `this script <https://raw.github.com/ansible/ansible/devel/plugins/inventory/cobbler.py>`_ to /etc/ansible/hosts and `chmod +x` the file. cobblerd will now need
|
||||
to be running when you are using Ansible.
|
||||
|
||||
Test the file by running `./etc/ansible/hosts` directly. You should see some JSON data output, but it may not have
|
||||
anything in it just yet.
|
||||
|
||||
Let's explore what this does. In cobbler, assume a scenario somewhat like the following::
|
||||
|
||||
cobbler profile add --name=webserver --distro=CentOS6-x86_64
|
||||
cobbler profile edit --name=webserver --mgmt-classes="webserver" --ksmeta="a=2 b=3"
|
||||
cobbler system edit --name=foo --dns-name="foo.example.com" --mgmt-classes="atlanta" --ksmeta="c=4"
|
||||
cobbler system edit --name=bar --dns-name="bar.example.com" --mgmt-classes="atlanta" --ksmeta="c=5"
|
||||
|
||||
In the example above, the system 'foo.example.com' will be addressable by ansible directly, but will also be addressable when using the group names 'webserver' or 'atlanta'. Since Ansible uses SSH, we'll try to contract system foo over 'foo.example.com', only, never just 'foo'. Similarly, if you try "ansible foo" it wouldn't find the system... but "ansible 'foo*'" would, because the system DNS name starts with 'foo'.
|
||||
|
||||
The script doesn't just provide host and group info. In addition, as a bonus, when the 'setup' module is run (which happens automatically when using playbooks), the variables 'a', 'b', and 'c' will all be auto-populated in the templates::
|
||||
|
||||
# file: /srv/motd.j2
|
||||
Welcome, I am templated with a value of a={{ a }}, b={{ b }}, and c={{ c }}
|
||||
|
||||
Which could be executed just like this::
|
||||
|
||||
ansible webserver -m setup
|
||||
ansible webserver -m template -a "src=/tmp/motd.j2 dest=/etc/motd"
|
||||
|
||||
.. note::
|
||||
The name 'webserver' came from cobbler, as did the variables for
|
||||
the config file. You can still pass in your own variables like
|
||||
normal in Ansible, but variables from the external inventory script
|
||||
will override any that have the same name.
|
||||
|
||||
So, with the template above (motd.j2), this would result in the following data being written to /etc/motd for system 'foo'::
|
||||
|
||||
Welcome, I am templated with a value of a=2, b=3, and c=4
|
||||
|
||||
And on system 'bar' (bar.example.com)::
|
||||
|
||||
Welcome, I am templated with a value of a=2, b=3, and c=5
|
||||
|
||||
And technically, though there is no major good reason to do it, this also works too::
|
||||
|
||||
ansible webserver -m shell -a "echo {{ a }}"
|
||||
|
||||
So in other words, you can use those variables in arguments/actions as well. You might use this to name
|
||||
a conf.d file appropriately or something similar. Who knows?
|
||||
|
||||
So that's the Cobbler integration support -- using the cobbler script as an example, it should be trivial to adapt Ansible to pull inventory, as well as variable information, from any data source. If you create anything interesting, please share with the mailing list, and we can keep it in the source code tree for others to use.
|
||||
|
||||
Example: AWS EC2 External Inventory Script
|
||||
``````````````````````````````````````````
|
||||
|
||||
If you use Amazon Web Services EC2, maintaining an inventory file might not be the best approach. For this reason, you can use the `EC2 external inventory <https://raw.github.com/ansible/ansible/devel/plugins/inventory/ec2.py>`_ script.
|
||||
|
||||
You can use this script in one of two ways. The easiest is to use Ansible's ``-i`` command line option and specify the path to the script.
|
||||
|
||||
ansible -i ec2.py -u ubuntu us-east-1d -m ping
|
||||
|
||||
The second option is to copy the script to `/etc/ansible/hosts` and `chmod +x` it. You will also need to copy the `ec2.ini <https://raw.github.com/ansible/ansible/devel/plugins/inventory/ec2.ini>`_ file to `/etc/ansible/ec2.ini`. Then you can run ansible as you would normally.
|
||||
|
||||
To successfully make an API call to AWS, you will need to configure Boto (the Python interface to AWS). There are a `variety of methods <http://docs.pythonboto.org/en/latest/boto_config_tut.html>`_ available, but the simplest is just to export two environment variables:
|
||||
|
||||
export AWS_ACCESS_KEY_ID='AK123'
|
||||
export AWS_SECRET_ACCESS_KEY='abc123'
|
||||
|
||||
You can test the script by itself to make sure your config is correct
|
||||
|
||||
cd plugins/inventory
|
||||
./ec2.py --list
|
||||
|
||||
After a few moments, you should see your entire EC2 inventory across all regions in JSON.
|
||||
|
||||
Since each region requires its own API call, if you are only using a small set of regions, feel free to edit ``ec2.ini`` and list only the regions you are interested in. There are other config options in ``ec2.ini`` including cache control, and destination variables.
|
||||
|
||||
At their heart, inventory files are simply a mapping from some name to a destination address. The default ``ec2.ini`` settings are configured for running Ansible from outside EC2 (from your laptop for example). If you are running Ansible from within EC2, internal DNS names and IP addresses may make more sense than public DNS names. In this case, you can modify the ``destination_variable`` in ``ec2.ini`` to be the private DNS name of an instance. This is particularly important when running Ansible within a private subnet inside a VPC, where the only way to access an instance is via its private IP address. For VPC instances, `vpc_destination_variable` in ``ec2.ini`` provides a means of using which ever `boto.ec2.instance variable <http://docs.pythonboto.org/en/latest/ref/ec2.html#module-boto.ec2.instance>`_ makes the most sense for your use case.
|
||||
|
||||
The EC2 external inventory provides mappings to instances from several groups:
|
||||
|
||||
Instance ID
|
||||
These are groups of one since instance IDs are unique.
|
||||
e.g.
|
||||
``i-00112233``
|
||||
``i-a1b1c1d1``
|
||||
|
||||
Region
|
||||
A group of all instances in an AWS region.
|
||||
e.g.
|
||||
``us-east-1``
|
||||
``us-west-2``
|
||||
|
||||
Availability Zone
|
||||
A group of all instances in an availability zone.
|
||||
e.g.
|
||||
``us-east-1a``
|
||||
``us-east-1b``
|
||||
|
||||
Security Group
|
||||
Instances belong to one or more security groups. A group is created for each security group, with all characters except alphanumerics, dashes (-) converted to underscores (_). Each group is prefixed by ``security_group_``
|
||||
e.g.
|
||||
``security_group_default``
|
||||
``security_group_webservers``
|
||||
``security_group_Pete_s_Fancy_Group``
|
||||
|
||||
Tags
|
||||
Each instance can have a variety of key/value pairs associated with it called Tags. The most common tag key is 'Name', though anything is possible. Each key/value pair is its own group of instances, again with special characters converted to underscores, in the format ``tag_KEY_VALUE``
|
||||
e.g.
|
||||
``tag_Name_Web``
|
||||
``tag_Name_redis-master-001``
|
||||
``tag_aws_cloudformation_logical-id_WebServerGroup``
|
||||
|
||||
When the Ansible is interacting with a specific server, the EC2 inventory script is called again with the ``--host HOST`` option. This looks up the HOST in the index cache to get the instance ID, and then makes an API call to AWS to get information about that specific instance. It then makes information about that instance available as variables to your playbooks. Each variable is prefixed by ``ec2_``. Here are some of the variables available:
|
||||
|
||||
- ec2_architecture
|
||||
- ec2_description
|
||||
- ec2_dns_name
|
||||
- ec2_id
|
||||
- ec2_image_id
|
||||
- ec2_instance_type
|
||||
- ec2_ip_address
|
||||
- ec2_kernel
|
||||
- ec2_key_name
|
||||
- ec2_launch_time
|
||||
- ec2_monitored
|
||||
- ec2_ownerId
|
||||
- ec2_placement
|
||||
- ec2_platform
|
||||
- ec2_previous_state
|
||||
- ec2_private_dns_name
|
||||
- ec2_private_ip_address
|
||||
- ec2_public_dns_name
|
||||
- ec2_ramdisk
|
||||
- ec2_region
|
||||
- ec2_root_device_name
|
||||
- ec2_root_device_type
|
||||
- ec2_security_group_ids
|
||||
- ec2_security_group_names
|
||||
- ec2_spot_instance_request_id
|
||||
- ec2_state
|
||||
- ec2_state_code
|
||||
- ec2_state_reason
|
||||
- ec2_status
|
||||
- ec2_subnet_id
|
||||
- ec2_tag_Name
|
||||
- ec2_tenancy
|
||||
- ec2_virtualization_type
|
||||
- ec2_vpc_id
|
||||
|
||||
Both ``ec2_security_group_ids`` and ``ec2_security_group_names`` are comma-separated lists of all security groups. Each EC2 tag is a variable in the format ``ec2_tag_KEY``.
|
||||
|
||||
To see the complete list of variables available for an instance, run the script by itself::
|
||||
|
||||
cd plugins/inventory
|
||||
./ec2.py --host ec2-12-12-12-12.compute-1.amazonaws.com
|
||||
|
||||
Example: OpenStack Inventory Script
|
||||
```````````````````````````````````
|
||||
|
||||
Though not detailed here in as much depth as the EC2 module, there's also a OpenStack Compute external inventory source in the plugins directory. It requires the Grizzly release of OpenStack or
|
||||
later. See the inline comments in the module source for how to use it.
|
||||
|
||||
Callback Plugins
|
||||
----------------
|
||||
|
||||
Ansible can be configured via code to respond to external events. This can include enhancing logging, signalling an external software
|
||||
system, or even (yes, really) making sound effects. Some examples are contained in the plugins directory.
|
||||
|
||||
Connection Type Plugins
|
||||
-----------------------
|
||||
|
||||
By default, ansible ships with a 'paramiko' SSH, native ssh (just called 'ssh'), and 'local' connection type, and an accelerated connection type named 'fireball'. All of these can be used
|
||||
in playbooks and with /usr/bin/ansible to decide how you want to talk to remote machines. The basics of these connection types
|
||||
are covered in the 'getting started' section. Should you want to extend Ansible to support other transports (SNMP? Message bus?
|
||||
Carrier Pigeon?) it's as simple as copying the format of one of the existing modules and dropping it into the connection plugins
|
||||
directory. The value of 'smart' for a connection allows selection of paramiko or openssh based on system capabilities, and chooses
|
||||
'ssh' if OpenSSH supports ControlPersist, in Ansible 1.2.1 an later. Previous versions did not support 'smart'.
|
||||
|
||||
Lookup Plugins
|
||||
--------------
|
||||
|
||||
Language constructs like "with_fileglob" and "with_items" are implemented via lookup plugins. Just like other plugin types, you can write your own.
|
||||
|
||||
Vars Plugins
|
||||
------------
|
||||
|
||||
Playbook constructs like 'host_vars' and 'group_vars' work via 'vars' plugins. They inject additional variable
|
||||
data into ansible runs that did not come from an inventory, playbook, or command line. Note that variables
|
||||
can also be returned from inventory, so in most cases, you won't need to write or understand vars_plugins.
|
||||
|
||||
Filter Plugins
|
||||
--------------
|
||||
|
||||
If you want more Jinja2 filters available in a Jinja2 template (filters like to_yaml and to_json are provided by default), they can be extended by writing a filter plugin.
|
||||
|
||||
Distributing Plugins
|
||||
--------------------
|
||||
|
||||
.. versionadded:: 0.8
|
||||
|
||||
Plugins are loaded from both Python's site_packages (those that ship with ansible) and a configured plugins directory, which defaults
|
||||
to /usr/share/ansible/plugins, in a subfolder for each plugin type::
|
||||
|
||||
* action_plugins
|
||||
* lookup_plugins
|
||||
* callback_plugins
|
||||
* connection_plugins
|
||||
* filter_plugins
|
||||
* vars_plugins
|
||||
|
||||
To change this path, edit the ansible configuration file.
|
||||
|
||||
In addition, plugins can be shipped in a subdirectory relative to a top-level playbook, in folders named the same as indicated above.
|
||||
|
||||
.. seealso::
|
||||
|
||||
:doc:`modules`
|
||||
List of built-in modules
|
||||
`Mailing List <http://groups.google.com/group/ansible-project>`_
|
||||
Questions? Help? Ideas? Stop by the list on Google Groups
|
||||
`irc.freenode.net <http://irc.freenode.net>`_
|
||||
#ansible IRC chat channel
|
||||
|
||||
@ -0,0 +1,54 @@
|
||||
|
||||
|
||||
Asynchronous Actions and Polling
|
||||
================================
|
||||
|
||||
By default tasks in playbooks block, meaning the connections stay open
|
||||
until the task is done on each node. This may not always be desirable, or you may
|
||||
be running operations that take longer than the SSH timeout.
|
||||
|
||||
The easiest way to do this is
|
||||
to kick them off all at once and then poll until they are done.
|
||||
|
||||
You will also want to use asynchronous mode on very long running
|
||||
operations that might be subject to timeout.
|
||||
|
||||
To launch a task asynchronously, specify its 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 `poll`::
|
||||
|
||||
---
|
||||
- hosts: all
|
||||
remote_user: root
|
||||
tasks:
|
||||
- name: simulate long running op (15 sec), wait for up to 45, poll every 5
|
||||
command: /bin/sleep 15
|
||||
async: 45
|
||||
poll: 5
|
||||
|
||||
.. note::
|
||||
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.
|
||||
|
||||
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::
|
||||
|
||||
---
|
||||
- hosts: all
|
||||
remote_user: root
|
||||
tasks:
|
||||
- name: simulate long running op, allow to run for 45, fire and forget
|
||||
command: /bin/sleep 15
|
||||
async: 45
|
||||
poll: 0
|
||||
|
||||
.. note::
|
||||
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.
|
||||
|
||||
.. note::
|
||||
Using a higher value for ``--forks`` will result in kicking off asynchronous
|
||||
tasks even faster. This also increases the efficiency of polling.
|
||||
|
||||
@ -0,0 +1,260 @@
|
||||
Conditionals
|
||||
============
|
||||
|
||||
Often the result of a play may depend on the value of a variable, fact (something learned about the remote system),
|
||||
or previous task result. In some cases, the values of variables may depend on other variables.
|
||||
Further, additional groups can be created to manage hosts based on
|
||||
whether the hosts match other criteria. There are many options to control execution flow in Ansible.
|
||||
|
||||
Let's dig into what they are.
|
||||
|
||||
.. contents::
|
||||
:depth: 2
|
||||
|
||||
The When Statement
|
||||
``````````````````
|
||||
|
||||
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.
|
||||
|
||||
This is easy to do in Ansible, with the `when` clause, which contains a Jinja2 expression (see `playbooks_variables`).
|
||||
It's actually pretty simple:
|
||||
|
||||
tasks:
|
||||
- name: "shutdown Debian flavored systems"
|
||||
command: /sbin/shutdown -t now
|
||||
when: ansible_os_family == "Debian"
|
||||
|
||||
A number of Jinja2 "filters" can also be used in when statements, some of which are unique
|
||||
and provided by Ansible. Suppose we want to ignore the error of one statement and then
|
||||
decide to do something conditionally based on success or failure::
|
||||
|
||||
tasks:
|
||||
- command: /bin/false
|
||||
register: result
|
||||
ignore_errors: True
|
||||
- command: /bin/something
|
||||
when: result|failed
|
||||
- command: /bin/something_else
|
||||
when: result|success
|
||||
- command: /bin/still/something_else
|
||||
when: result|skipped
|
||||
|
||||
Note that was a little bit of foreshadowing on the 'register' statement. We'll get to it a bit later in this chapter.
|
||||
|
||||
As a reminder, to see what facts are available on a particular system, you can do::
|
||||
|
||||
ansible hostname.example.com -m setup
|
||||
|
||||
Tip: Sometimes you'll get back a variable that's a string and you'll want to do a math operation comparison on it. You can do this like so::
|
||||
|
||||
tasks:
|
||||
- shell: echo "only on Red Hat 6, derivatives, and later"
|
||||
when: ansible_os_family == "RedHat" and ansible_lsb.major_release|int >= 6
|
||||
|
||||
.. note:: the above example requires the lsb_release package on the target host in order to return the ansible_lsb.major_release fact.
|
||||
|
||||
Variables defined in the playbooks or inventory can also be used. An example may be the execution of a task based on a variable's boolean value::
|
||||
|
||||
vars:
|
||||
epic: true
|
||||
|
||||
Then a conditional execution might look like::
|
||||
|
||||
tasks:
|
||||
- shell: echo "This certainly is epic!"
|
||||
when: epic
|
||||
|
||||
or::
|
||||
|
||||
tasks:
|
||||
- shell: echo "This certainly isn't epic!"
|
||||
when: not epic
|
||||
|
||||
If a required variable has not been set, you can skip or fail using Jinja2's
|
||||
`defined` test. For example::
|
||||
|
||||
tasks:
|
||||
- shell: echo "I've got '{{ foo }}' and am not afraid to use it!"
|
||||
when: foo is defined
|
||||
|
||||
- fail: msg="Bailing out: this play requires 'bar'"
|
||||
when: bar is not defined
|
||||
|
||||
This is especially useful in combination with the conditional import of vars
|
||||
files (see below).
|
||||
|
||||
.. note :: When combining `when` with `with_items`, be aware that the `when` statement is processed separately for each item.
|
||||
This is by design::
|
||||
|
||||
tasks:
|
||||
- command: echo {{ item }}
|
||||
with_items: [ 0, 2, 4, 6, 8, 10 ]
|
||||
when: item > 5
|
||||
|
||||
Loading in Custom Facts
|
||||
```````````````````````
|
||||
|
||||
It's also easy to provide your own facts if you want, which is covered in :doc:`moduledev`. To run them, just
|
||||
make a call to your own custom fact gathering module at the top of your list of tasks, and variables returned
|
||||
there will be accessible to future tasks::
|
||||
|
||||
tasks:
|
||||
- name: gather site specific fact data
|
||||
action: site_facts
|
||||
- command: /usr/bin/thingy
|
||||
when: "{{ my_custom_fact_just_retrieved_from_the_remote_system }} == '1234'"
|
||||
|
||||
The Register Keyword
|
||||
````````````````````
|
||||
|
||||
The 'register' keyword saves the result of a command in a variable. Use "-v" on the playbook command line to see
|
||||
what kind of values are available, but there are many.
|
||||
|
||||
One useful trick with *when* is to key off the result of a last command. As an example::
|
||||
|
||||
tasks:
|
||||
- template: src=/templates/foo.j2 dest=/etc/foo.conf
|
||||
register: last_result
|
||||
- command: echo 'the file has changed'
|
||||
when: last_result.changed
|
||||
|
||||
{{ last_result }} is a variable set by the register directive. This assumes Ansible 0.8 and later.
|
||||
|
||||
Applying 'when' to roles and includes
|
||||
`````````````````````````````````````
|
||||
|
||||
Note that if you have several tasks that all share the same conditional statement, you can affix the conditional
|
||||
to a task include statement as below. Note this does not work with playbook includes, just task includes. All the tasks
|
||||
get evaluated, but the conditional is applied to each and every task::
|
||||
|
||||
- include: tasks/sometasks.yml
|
||||
when: "'reticulating splines' in output"
|
||||
|
||||
Or with a role::
|
||||
|
||||
- hosts: webservers
|
||||
roles:
|
||||
- { role: debian_stock_config, when: ansible_os_family == 'Debian' }
|
||||
|
||||
You will note a lot of 'skipped' output by default in Ansible when using this approach on systems that don't match the criteria.
|
||||
Read up on the 'group_by' module in the `modules` docs for a more streamlined way to accomplish the same thing.
|
||||
|
||||
Conditional Imports
|
||||
```````````````````
|
||||
|
||||
.. note:: This is an advanced topic that is infrequently used. You can probably skip this section.
|
||||
|
||||
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.
|
||||
|
||||
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::
|
||||
|
||||
---
|
||||
- hosts: all
|
||||
remote_user: root
|
||||
vars_files:
|
||||
- "vars/common.yml"
|
||||
- [ "vars/{{ ansible_os_family }}.yml", "vars/os_defaults.yml" ]
|
||||
tasks:
|
||||
- name: make sure apache is running
|
||||
service: name={{ apache }} state=running
|
||||
|
||||
.. note::
|
||||
The variable 'ansible_os_family' is being interpolated into
|
||||
the list of filenames being defined for vars_files.
|
||||
|
||||
As a reminder, the various YAML files contain just keys and values::
|
||||
|
||||
---
|
||||
# for vars/CentOS.yml
|
||||
apache: httpd
|
||||
somethingelse: 42
|
||||
|
||||
How does this work? If the operating system was 'CentOS', the first file Ansible would try to import
|
||||
would be 'vars/CentOS.yml', followed 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.
|
||||
|
||||
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::
|
||||
|
||||
# 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"
|
||||
|
||||
Ansible's approach to configuration -- separating 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.
|
||||
|
||||
Selecting Files And Templates Based On Variables
|
||||
````````````````````````````````````````````````
|
||||
|
||||
.. note:: This is an advanced topic that is infrequently used. You can probably skip this section.
|
||||
|
||||
Sometimes a configuration file you want to copy, or a template you will use may depend on a variable.
|
||||
The following construct selects the first available file appropriate for the variables of a given host, which is often much cleaner than putting a lot of if conditionals in a template.
|
||||
|
||||
The following example shows how to template out a configuration file that was very different between, say, CentOS and Debian::
|
||||
|
||||
- name: template a file
|
||||
template: src={{ item }} dest=/etc/myapp/foo.conf
|
||||
with_first_found:
|
||||
files:
|
||||
- {{ ansible_distribution }}.conf
|
||||
- default.conf
|
||||
paths:
|
||||
- search_location_one/somedir/
|
||||
- /opt/other_location/somedir/
|
||||
|
||||
Register Variables
|
||||
``````````````````
|
||||
|
||||
.. versionadded:: 0.7
|
||||
|
||||
Often in a playbook it may be useful to store the result of a given command in a variable and access
|
||||
it later. Use of the command module in this way can in many ways eliminate the need to write site specific facts, for
|
||||
instance, you could test for the existence of a particular program.
|
||||
|
||||
The 'register' keyword decides what variable to save a result in. The resulting variables can be used in templates, action lines, or *when* statements. It looks like this (in an obviously trivial example)::
|
||||
|
||||
- name: test play
|
||||
hosts: all
|
||||
|
||||
tasks:
|
||||
|
||||
- shell: cat /etc/motd
|
||||
register: motd_contents
|
||||
|
||||
- shell: echo "motd contains the word hi"
|
||||
when: motd_contents.stdout.find('hi') != -1
|
||||
|
||||
As shown previously, the registered variable's string contents are accessible with the 'stdout' value.
|
||||
The registered result can be used in the "with_items" of a task if it is converted into
|
||||
a list (or already is a list) as shown below. "stdout_lines" is already available on the object as
|
||||
well though you could also call "home_dirs.stdout.split()" if you wanted, and could split by other
|
||||
fields::
|
||||
|
||||
- name: registered variable usage as a with_items list
|
||||
hosts: all
|
||||
|
||||
tasks:
|
||||
|
||||
- name: retrieve the list of home directories
|
||||
command: ls /home
|
||||
register: home_dirs
|
||||
|
||||
- name: add home dirs to the backup spooler
|
||||
file: path=/mnt/bkspool/{{ item }} src=/home/{{ item }} state=link
|
||||
with_items: home_dirs.stdout_lines
|
||||
# same as with_items: home_dirs.stdout.split()
|
||||
|
||||
|
||||
|
||||
File diff suppressed because it is too large
Load Diff
File diff suppressed because it is too large
Load Diff
Loading…
Reference in New Issue