Calculate Quorum of Hosts

Problem

How do we calculate the quorum of Hosts in a Play?

Solution

quorum: "{{ ( group['cluster_leaders'] | count / 2) | round(0, 'ceil') | int }}"

Explanation

A list of Hosts serves as the origin.

- name: Calculate quorum of cluster leaders
  ansible.builtin.copy:
    content: "{{ ( group['cluster_leaders'] | count / 2) | round(0, 'ceil') | int }}"
    dest: /etc/cluster-leader/quorum

Group, Lookup or Query

In our solution, we used a group group['my_group'] but a Lookup or Query may also be suitable when using groups with filters:

"{{ query('inventory_hostnames', 'cluster_leaders:!cluster_followers') }}"

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