redis/tasks/discover_master.yaml

---
- name: Discover redis with master role
  shell: redis-cli --pass {{ redis_requirepass }} info replication | grep 'role:master'
  register: redis_master
  changed_when: False
  failed_when: False

- name: Set fact about redis master
  set_fact:
    redis_master_ip: "{{ hostvars[inventory_hostname].ansible_default_ipv4.address | default(hostvars[play_hosts[0]].ansible_default_ipv4.address) }}"
  delegate_to: "{{ item }}"
  delegate_facts: true
  loop: "{{ play_hosts }}"
  when: redis_master.rc == 0

- name: Set fact about redis master
  set_fact:
    redis_master_ip: "{{ hostvars[play_hosts[0]].ansible_default_ipv4.address }}"
  when: redis_master_ip is not defined

- debug:
    msg: "Master redis IP is {{ redis_master_ip }}"
    verbosity: 2