CODEWITHSUNDEEP
ansible
moritz
moritz

Reputation: 3

Ansible: Create a dynamic hostgroup based on host variables

Is it possible to auto create a host group based on manually defined host variables?

This is my inventory:

[webserver]
web1         ansible_host=192.168.20.1     production=False
web2         ansible_host=192.168.20.2     production=False
web3         ansible_host=192.168.20.3     production=True
web4         ansible_host=192.168.20.4     production=True
...

I want to have a dynamic hostgroup, e.g., webserver_production and use this as target.

Is there another way to do archive this? Thank you.

Upvotes: 0

Views: 93

Answers (1)

Vladimir Botka
Vladimir Botka

Reputation: 68189

Use the inventory plugin constructed. See

shell> ansible-doc -t inventory constructed
  1. Create the inventory
shell> tree inventory/
inventory/
├── 01-webserver
└── 02-webserver_production.yml

0 directories, 2 files

shell> cat inventory/01-webserver
[webserver]
web1 ansible_host=192.168.20.1 production=False
web2 ansible_host=192.168.20.2 production=False
web3 ansible_host=192.168.20.3 production=True
web4 ansible_host=192.168.20.4 production=True

shell> cat inventory/02-webserver_production.yml
plugin: constructed
groups:
  webserver_production: production
  1. Test the inventory
shell> ansible-inventory -i inventory --list --yaml
all:
  children:
    ungrouped: {}
    webserver:
      hosts:
        web1:
          ansible_host: 192.168.20.1
          production: false
        web2:
          ansible_host: 192.168.20.2
          production: false
        web3:
          ansible_host: 192.168.20.3
          production: true
        web4:
          ansible_host: 192.168.20.4
          production: true
    webserver_production:
      hosts:
        web3: {}
        web4: {}
  1. Test the inventory in a playbook
shell> cat pb.yml
- hosts: webserver
  gather_facts: false
  tasks:
    - debug:
        var: ansible_play_hosts_all
      run_once: true

- hosts: webserver_production
  gather_facts: false
  tasks:
    - debug:
        var: ansible_play_hosts_all
      run_once: true

gives (abridged)

shell> ansible-playbook -i inventory pb.yml

PLAY [webserver] *****************************************************************************

TASK [debug] *********************************************************************************
ok: [web1] => 
  ansible_play_hosts_all:
  - web1
  - web2
  - web3
  - web4

PLAY [webserver_production] ******************************************************************

TASK [debug] *********************************************************************************
ok: [web3] => 
  ansible_play_hosts_all:
  - web3
  - web4

Notes:

  • The files in the directory inventory are evaluated in alphabetical order.

  • See Special Variables ansible_play_hosts, ansible_play_hosts_all, ...

Upvotes: 2

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