increase_node_memory.yml

---
- name: Increase node memory
  hosts: localhost
  connection: local
  gather_facts: false

  # These variables are intended to be overriden using the `--extra-vars`
  # command line option:
  vars:
    # Maximum memory to assing to the VM, in MiB.
    max_memory: 4096
    # Amount of memory to add in each increase, in MiB. Must be a multiple of
    # 256 MiB due to restrictions in the oVirt API.
    inc_memory: 256

  tasks:

  # Calculate the IP address from the `instance` input variable, and then do a
  # reverse DNS lookup to find the FQDN, which in this environment is equal to
  # the name of the virtual machine.
  - set_fact:
      vm_ip: "{{ instance | regex_replace(':.*$') }}"
  - set_fact:
      vm_name: "{{ lookup('dig', vm_ip + '/PTR') | regex_replace('\\.$') }}"

  # Retrieve the facts of the virtual machine, so that we can check that it
  # exists and get its current memory size:
  - ovirt_vms_facts:
      pattern: "name={{ vm_name }}"
  - debug:
      var: ovirt_vms

  # Fail if the virtual machine doesn't exist:
  - fail:
      msg: "Virtual machine '{{ vm_name }}' doesn't exist"
    when: ovirt_vms | length == 0

  # Extract the current memory:
  - set_fact:
      current_memory: "{{ ovirt_vms[0].memory / 2**20 }}"
  - debug:
      var: current_memory

  # Calculate the new amount of memory:
  - set_fact:
      new_memory: "{{ [current_memory|int + inc_memory|int, max_memory|int] | min }}"
  - debug:
      var: new_memory

  # Update the virtual machine with the new memory size:
  - name: Increase memory of '{{ vm_name }}'
    ovirt_vms:
      name: "{{ vm_name }}"
      memory: "{{ new_memory }}MiB"
    when: new_memory > current_memory