ansible - example of custom module to gather info on installed packages

01_gather_installed.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-

# Note: only works on RedHat family
# This library should be saved to the 'library/' folder relative to your playbooks/inventory

import rpm

def _check_installed(module):
  ts = rpm.TransactionSet()
  mi = ts.dbMatch()

  results = []
  for h in mi:
    results.append(h['name'])

  return { 'ansible_facts': { 'packages_installed': results } }

def main():
  module = AnsibleModule(
      argument_spec = dict(
    ),
    supports_check_mode = True,
  )
  data = _check_installed(module)
  module.exit_json(**data)

from ansible.module_utils.basic import *
main()

02_play.yml

- hosts: foo
  tasks:
    - gather_installed:

    - debug: var=hostvars[inventory_hostname]['packages_installed']

    - debug: msg='do something when httpd is installed'
      when: "'httpd' in packages_installed"

03_output

PLAY [foo] ******************************************************************** 

GATHERING FACTS *************************************************************** 
ok: [localhost]

TASK: [gather_installed ] ***************************************************** 
ok: [localhost]

TASK: [debug var=hostvars[inventory_hostname]['packages_installed']] ********** 
ok: [localhost] => {
    "hostvars[inventory_hostname]['packages_installed']": [
        "perl-version",
        "xz-lzma-compat",
        "fontpackages-filesystem",
        "perl-Digest-SHA",
        "openconnect",
        "libattr",
...
        "python-pycurl",
        "dhclient",
        "libICE"
    ]
}

TASK: [debug msg='do something when httpd is installed'] **********************
ok: [localhost] => {
    "msg": "do something when httpd is installed"
}