pg_upgrade_rollback.yml

---
# This playbook performs a rollback of a PostgreSQL upgrade.
# It's designed to be used when a PostgreSQL upgrade hasn't been fully completed and the new version hasn't been started.
# The rollback operation is performed by starting the Patroni cluster with the old version of PostgreSQL using the same PGDATA.
# The playbook first checks the health of the current cluster, verifies the version of PostgreSQL, and ensures the new PostgreSQL is not running.
# If these checks pass, the playbook switches back to the old PostgreSQL paths and restarts the Patroni service.

- name: "pg_upgrade_rollback.yml | Rollback the PostgreSQL upgrade"
  hosts: postgres_cluster
  gather_facts: true
  any_errors_fatal: true
  pre_tasks:
    - name: "Set variable: ansible_python_interpreter"
      ansible.builtin.set_fact:
        ansible_python_interpreter: "/usr/bin/env python3"
      when: "'python3' not in (ansible_python_interpreter | default(''))"

    - name: Include main variables
      ansible.builtin.include_vars: "vars/main.yml"
    - name: Include upgrade variables
      ansible.builtin.include_vars: "vars/upgrade.yml"
  tasks:
    - name: '[Prepare] Add host to group "primary" (in-memory inventory)'
      ansible.builtin.add_host:
        name: "{{ item }}"
        groups: primary
      # As Primary we specify the host in the 'master' group in the inventory file.
      loop: "{{ groups['master'] }}"
      changed_when: false

    - name: '[Prepare] Add hosts to group "secondary" (in-memory inventory)'
      ansible.builtin.add_host:
        name: "{{ item }}"
        groups: secondary
      # As Secondary we specify the hosts in the 'replica' group in the inventory file.
      loop: "{{ groups['replica'] }}"
      changed_when: false
  tags:
    - always

- name: "Perform Rollback"
  hosts: 'primary:secondary'
  gather_facts: false
  become: true
  become_user: postgres
  any_errors_fatal: true
  pre_tasks:
    - name: Include main variables
      ansible.builtin.include_vars: "vars/main.yml"
    - name: Include OS-specific variables
      ansible.builtin.include_vars: "vars/{{ ansible_os_family }}.yml"
    - name: Include upgrade variables
      ansible.builtin.include_vars: "vars/upgrade.yml"
  tasks:
    - name: Running rollback.yml
      ansible.builtin.include_role:
        name: upgrade
        tasks_from: rollback
  tags:
    - rollback