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README.md

Ansible inventory plugins new in 2.4

Starting in 2.4, users are nudged to move to plugins as opposed to inventory scripts.

Some links on the subject:

The old inventory scripts:

Simple example of configuring plugins

Turn off a needed plugin, and watch the inventory fail.

export ANSIBLE_INVENTORY_ENABLED=script
ansible-inventory -i official/inventory.ini --list

[WARNING]: Unable to parse <...>/official/inventory.ini as an inventory source

In this example, it can not parse the contents of the file, because the ini inventory plugin is not available.

export ANSIBLE_INVENTORY_ENABLED=ini
ansible-inventory -i official/inventory.ini --list

That works.

Ansible will not accept an invalid plugin name.

export ANSIBLE_INVENTORY_ENABLED=foobar

[WARNING]: Failed to load inventory plugin, skipping foobar

The "constructed" built-in plugin

Some plugin examples do not actually return content containing hosts, but will modify content from another source. The "constructed" plugin is the most important example of this at the current time:

export ANSIBLE_INVENTORY_ENABLED=ini,constructed
ansible-inventory -i plugins/example_hosts/constructed_hosts -i plugins/constructed.config --list

The plugins list allows the first file (defining the hosts) to be interpreted via the ini plugin. Then the 2nd inventory given by the -i flag will grok the contents of constructed.config, which modifies the inventory contents dynamically.

constructed.config sorts the hosts from constructed_hosts into groups. As a case-in-point, the host websomething is put into the webservers because its name starts with "web". This is a rule defined in the constructed.config file.

The "constructed" inventory must be used after any other inventories that it is intended to operate on in the CLI args.

Using Openstack

In order to get this to work, you will have to edit the file plugins/example_openstack/openstack.yml, hard-coding in the path of your clone of this repo.

VERY IMPORTANT NOTE: you can not name this file something else. It must be openstack.yml or openstack.yaml or it will fail without any clear reason why.

You also need to put in your own authentication credentials into plugins/example_openstack/clouds.yml.

Additional pre-requisites are that you install the shade library, and that you specifically enable the openstack plugin. That is covered in the following lines:

pip install shade
export ANSIBLE_INVENTORY_ENABLED=openstack
ansible-inventory -i plugins/example_openstack/openstack.yml --list

This should produce the actual content.

Verification

We can verify this content by comparing it to the output of ansible-playbook:

ansible-playbook -i plugins/example_openstack/openstack.yml debugging/hostvars_print.yml

Also, we can compare the output to the old inventory script.

unset ANSIBLE_INVENTORY_ENABLED
export OS_CLIENT_CONFIG_FILE=<cwd>/plugins/example_openstack/clouds.yml
ansible-inventory -i <ansible source location>/contrib/inventory/ec2.py --list

Current testing shows that these methods produce very near the same data, although not exactly the same.

User-defined Plugin

In this case, you have written a plugin yourself, unlike the previous examples which all used plugins vendored with Ansible.

export ANSIBLE_INVENTORY_PLUGINS=$(PWD)/plugins/user_plugins/
ansible-doc -t inventory -l
ansible-doc -t inventory alan

(note, the ansible-doc commands are fixed as of Ansible PR #31996, Ansible 2.4.2 or higher is needed)

If that is working, it should be feasible to do the following:

export ANSIBLE_INVENTORY_ENABLED=alan
ansible-inventory -i top_level_file.ini --list

No matter what inventory file you give it in this case, the output should just have a host named "alan".

Relative path

If you have a folder named inventory_plugins inside your current working directory, Ansible will use that.

cd plugins/user_plugins_rel/
export ANSIBLE_INVENTORY_ENABLED=alan
ansible-inventory -i foobar.ini --list

result:

ansible-inventory -i foobar.ini --list
{
    "_meta": {
        "hostvars": {
            "alan": {
                "ansible_port": 8928
            }
        }
    }, 
    "all": {
        "children": [
            "ungrouped"
        ]
    }, 
    "ungrouped": {
        "hosts": [
            "alan"
        ]
    }
}