how to use json file consisting of host info as input to ansible inventory

DSAK picture DSAK · Feb 8, 2018 · Viewed 9.6k times · Source

I am trying to use the following json file as input to ansible host inventory but I get error when I run the playbook. JSON File:

{
   "instances":{
       "host": 10.66.70.33
   }
}

Playbook:

hosts: "{{ instances.host }}"
remote_user: root #vars:

When I run the play book I get the following errors. I am not sure where I am doing wrong. I am new to Ansible. Please advice I guess i am doing some silly mistake.

[WARNING]: Could not match supplied host pattern, ignoring: all [WARNING]: provided hosts list is empty, only localhost is available ERROR! The field 'hosts' has an invalid value, which includes an undefined variable. The error was: 'instances' is undefined

I am running the playbook as follows:

ansible-playbook -i <path>/test.json <path>test_playbook.yml

Answer

kajahno picture kajahno · Feb 8, 2018

It seems pure JSON it's not supported as inventory file. In the inventory plugin list I don't see JSON:

  • advanced_host_list - Parses a ‘host list’ with ranges
  • auto - Loads and executes an inventory plugin specified in a YAML config
  • aws_ec2 - ec2 inventory source
  • constructed - Uses Jinja2 to construct vars and groups based on existing inventory.
  • host_list - Parses a ‘host list’ string
  • ini - Uses an Ansible INI file as inventory source.
  • k8s - Kubernetes (K8s) inventory source
  • openshift - OpenShift inventory source
  • openstack - OpenStack inventory source
  • script - Executes an inventory script that returns JSON
  • virtualbox - virtualbox inventory source
  • yaml - Uses a specifically YAML file as inventory source.

On the other hand you can wrap that JSON in a simple python script as follows:

  1. Make sure the script plugin is enabled in your ansible.cfg file:

    [inventory]
    enable_plugins = host_list, script, yaml, ini
    
  2. Create wrapper script (inventory file), only reads your JSON and prints it in the console (I'm assuming the JSON and the wrapper script are in the same path):

    #!/usr/bin/env python
    import os
    
    __location__ = os.path.realpath(
        os.path.join(os.getcwd(), os.path.dirname(__file__)))
    
    with open(os.path.join(__location__, "hosts.json")) as f:
        print f.read()
    
  3. Use the following in your JSON inventory (performance improvements):

    {
        "_meta": {
            "hostvars": { }
        },
    
        "instances": {
            "hosts": ["10.66.70.33"]
        }
    }
    
  4. When running the playbook just be aware the group you want to target should be "instances", for example this is my playbook:

    ---
    - hosts: instances
      tasks:
        - debug:
            msg: Hi there
    

Then just run the playbook as you did, specifying the python wrapper script, in my case this was:

ansible-playbook -i inventory/hostswrapper.py test-stkovfl.yml

Hope it helps!