Question 109358 in Json Question posted in
Our archive of expertly curated questions and answers provides insights and solutions to common problems related to this popular data interchange format. From parsing and manipulating JSON data to integrating it with various programming languages and web services, our archive has got you covered. Start exploring today and take your JSON skills to the next level

json filter in creating a jinja2 template

am trying to create my 1st jinja2 template that extracts a field from a json string as am trying to create DHCP reserveration file.

here is an example inventory feed.

I would like to select the value from the mac address to use as a value as jinja2 value for a field for the interface that matches the ansible host. which could be in any postion on the interfaces.

how would I go about it


 "TEST": {
                "ansible_host": "192.171.130.8",
                "interfaces": [
                    {
                        "ip_addresses": [
                            {
                                "address": "192.171.130.8/32",
                            }
                        ],
                        "mac_address": "C8-F1-13-78-9E-E7"
                        
                    },
                    {
                        "ip_addresses": [
                            {
                                "address": "192.171.130.80/32",
                            }
                        ],
                        "mac_address": "85-9F-76-AE-57-10"
                        
                    }
                ],
                
               
         }

so I would like to doe something like

{{ hostvars[host].interfaces.[ip_addresses.address = ansible_host].mac_address }}

but am not sure how to go about it.

Tags:

2

Answers


  1. 0

    This looks like a good candidate for the json_query filter. My first thought was that this should work:

    hostvars[host].interfaces | json_query("[?ip_addresses[].address == '192.171.130.8/32']")

    But that returns an empty list. The following is a bit more verbose, but produces the expected result:

    hostvars[host].interfaces|json_query("[?ip_addresses[].address | contains(@, '192.171.130.8/32')]")

    In a playbook:

    - hosts: localhost
  gather_facts: false
  vars:
    TEST: {
      "ansible_host": "192.171.130.8",
      "interfaces": [
        {
          "ip_addresses": [
            {
              "address": "192.171.130.8/32",
              }
              ],
          "mac_address": "C8-F1-13-78-9E-E7"

          },
          {
            "ip_addresses": [
              {
                "address": "192.171.130.80/32",
                }
                ],
            "mac_address": "85-9F-76-AE-57-10"

            }
            ],


          }
  tasks:
    - debug:
        msg: >-
          {{ TEST.interfaces | json_query("[?ip_addresses[].address | contains(@, '192.171.130.8/32')]") }}

    NB: Watch your quoting; you’ll note that here I’ve used the YAML folding quote operating (>) because the expression contains both double quotes and single quotes, so putting either of those around the outside would mean escaping quotes inside the expression.

    Running the above playbook produces:

    ok: [localhost] => {
    "msg": [
        {
            "ip_addresses": [
                {
                    "address": "192.171.130.8/32"
                }
            ],
            "mac_address": "C8-F1-13-78-9E-E7"
        }
    ]
}

    Since you’ve got the desired address in a variable (ansible_host), you would write instead:

      tasks:
    - debug:
        msg: >-
          {{
            hostvars[host].interfaces | json_query("[?ip_addresses[].address | contains(@, '%s/32')]" % ansible_host)
          }}

    Our expression returns a list containing a single dictionary. If you want the mac_address field, treat the result just like any other Ansible array variable:

      tasks:
    - debug:
        msg: >-
          {{
          (
            hostvars[host].interfaces |
            json_query("[?ip_addresses[].address | contains(@, '%s/32')]" % ansible_host)
          ).0.mac_address
          }}
    Login or Signup to reply.
  2. 0

    Create the dictionary from the MAC addresses and lists of IPs

      mac_ip_raw: "{{ dict(interfaces|json_query(mac_ip_query)) }}"
  mac_ip_query: '[].[mac_address, ip_addresses[].address]'

    gives

      mac_ip_raw:
    85-9F-76-AE-57-10:
    - 192.171.130.80/32
    C8-F1-13-78-9E-E7:
    - 192.171.130.8/32

    Get rid of the masks

      mac_ip: "{{ dict(mac_ip_raw.keys()|
                   zip(mac_ip_raw.values()|
                       map('map', 'split', '/')|
                       map('map', 'first'))) }}"

    gives

      mac_ip:
    85-9F-76-AE-57-10:
    - 192.171.130.80
    C8-F1-13-78-9E-E7:
    - 192.171.130.8

    Now, test which list contains the IP

      my_mac: "{{ mac_ip|dict2items|
              selectattr('value', 'contains', ansible_host)|
              map(attribute='key')|first }}"

    gives the expected result

      my_mac: C8-F1-13-78-9E-E7

    Example of a complete project for testing

    shell> tree .
.
├── ansible.cfg
├── hosts
├── host_vars
│   └── srv1
│       └── interfaces.json
└── pb.yml

2 directories, 4 files

    shell> cat ansible.cfg 
[defaults]
gathering = explicit
collections_path = $HOME/.local/lib/python3.9/site-packages/
inventory = $PWD/hosts
roles_path = $PWD/roles
retry_files_enabled = false
stdout_callback = yaml

    shell> cat hosts
srv1 ansible_host=192.171.130.8

    shell> cat host_vars/srv1/interfaces.json 
{
  "interfaces":
    [
        {
            "ip_addresses": [
                {
                    "address": "192.171.130.8/32"
                }
            ],
            "mac_address": "C8-F1-13-78-9E-E7"
        },
        {
            "ip_addresses": [
                {
                    "address": "192.171.130.80/32"
                }
            ],
            "mac_address": "85-9F-76-AE-57-10"
        }
    ]
}

    shell> cat pb.yml 
- hosts: all

  vars:

    mac_ip_raw: "{{ dict(interfaces|json_query(mac_ip_query)) }}"
    mac_ip_query: '[].[mac_address, ip_addresses[].address]'
    mac_ip: "{{ dict(mac_ip_raw.keys()|
                     zip(mac_ip_raw.values()|
                         map('map', 'split', '/')|
                         map('map', 'first'))) }}"
    my_mac: "{{ mac_ip|dict2items|
                selectattr('value', 'contains', ansible_host)|
                map(attribute='key')|first }}"
    
  tasks:

    - debug:
        var: ansible_host
    - debug:
        var: interfaces
    - debug:
        var: mac_ip_raw
    - debug:
        var: mac_ip
    - debug:
        var: my_mac

    Login or Signup to reply.
Please signup or login to give your own answer.

Back To Top
Search