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99 lines
3.7 KiB
ReStructuredText
99 lines
3.7 KiB
ReStructuredText
Developing Dynamic Inventory Sources
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====================================
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.. contents:: Topics
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:local:
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As described in :doc:`intro_dynamic_inventory`, ansible can pull inventory information from dynamic sources, including cloud sources.
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How do we write a new one?
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Simple! We just create a script or program that can print JSON in the right format when fed the proper arguments.
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You can do this in any language.
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.. _inventory_script_conventions:
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Script Conventions
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``````````````````
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When the external node script is called with the single argument ``--list``, the script must output a JSON encoded hash/dictionary of all the groups to be managed to stdout. 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::
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{
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"databases" : {
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"hosts" : [ "host1.example.com", "host2.example.com" ],
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"vars" : {
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"a" : true
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}
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},
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"webservers" : [ "host2.example.com", "host3.example.com" ],
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"atlanta" : {
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"hosts" : [ "host1.example.com", "host4.example.com", "host5.example.com" ],
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"vars" : {
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"b" : false
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},
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"children": [ "marietta", "5points" ]
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},
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"marietta" : [ "host6.example.com" ],
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"5points" : [ "host7.example.com" ]
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}
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.. versionadded:: 1.0
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Before version 1.0, each group could only have a list of hostnames/IP addresses, like the webservers, marietta, and 5points groups above.
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When called with the arguments ``--host <hostname>`` (where <hostname> is a host from above), the script must print either an empty JSON
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hash/dictionary, or a hash/dictionary of variables to make available to templates and playbooks. Printing variables is optional,
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if the script does not wish to do this, printing an empty hash/dictionary is the way to go::
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{
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"favcolor" : "red",
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"ntpserver" : "wolf.example.com",
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"monitoring" : "pack.example.com"
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}
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.. _inventory_script_tuning:
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Tuning the External Inventory Script
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````````````````````````````````````
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.. versionadded:: 1.3
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The stock inventory script system detailed above works for all versions of Ansible, but calling
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``--host`` for every host can be rather expensive, especially if it involves expensive API calls to
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a remote subsystem. In Ansible
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1.3 or later, if the inventory script returns a top level element called "_meta", it is possible
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to return all of the host variables in one inventory script call. When this meta element contains
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a value for "hostvars", the inventory script will not be invoked with ``--host`` for each host. This
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results in a significant performance increase for large numbers of hosts, and also makes client
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side caching easier to implement for the inventory script.
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The data to be added to the top level JSON dictionary looks like this::
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{
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# results of inventory script as above go here
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# ...
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"_meta" : {
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"hostvars" : {
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"moocow.example.com" : { "asdf" : 1234 },
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"llama.example.com" : { "asdf" : 5678 }
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}
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}
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}
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.. seealso::
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:doc:`developing_api`
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Python API to Playbooks and Ad Hoc Task Execution
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:doc:`developing_modules`
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How to develop modules
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:doc:`developing_plugins`
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How to develop plugins
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`Ansible Tower <http://ansible.com/ansible-tower>`_
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REST API endpoint and GUI for Ansible, syncs with dynamic inventory
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`Development Mailing List <http://groups.google.com/group/ansible-devel>`_
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Mailing list for development topics
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`irc.freenode.net <http://irc.freenode.net>`_
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#ansible IRC chat channel
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