ceph-ansible/infrastructure-playbooks/shrink-mon.yml

---
# This playbook shrinks the Ceph monitors from your cluster
# It can remove a Ceph of monitor from the cluster and ALL ITS DATA
#
# Use it like this:
# ansible-playbook shrink-mon.yml -e mon_to_kill=ceph-mon01
#     Prompts for confirmation to shrink, defaults to no and
#     doesn't shrink the cluster. yes shrinks the cluster.
#
# ansible-playbook -e ireallymeanit=yes|no shrink-mon.yml
#     Overrides the prompt using -e option. Can be used in
#     automation scripts to avoid interactive prompt.


- name: Gather facts and check the init system

  hosts: "{{ mon_group_name|default('mons') }}"

  become: true

  tasks:
    - name: Gather facts on all Ceph hosts for following reference
      ansible.builtin.debug:
        msg: "gather facts on all Ceph hosts for following reference"

- name: Confirm whether user really meant to remove monitor from the ceph cluster
  hosts: mons[0]
  become: true
  vars_prompt:
    - name: ireallymeanit  # noqa: name[casing]
      prompt: Are you sure you want to shrink the cluster?
      default: 'no'
      private: false
  vars:
    mon_group_name: mons

  pre_tasks:
    - name: Exit playbook, if only one monitor is present in cluster
      ansible.builtin.fail:
        msg: "You are about to shrink the only monitor present in the cluster.
              If you really want to do that, please use the purge-cluster playbook."
      when: groups[mon_group_name] | length | int == 1

    - name: Exit playbook, if no monitor was given
      ansible.builtin.fail:
        msg: "mon_to_kill must be declared
          Exiting shrink-cluster playbook, no monitor was removed.
           On the command line when invoking the playbook, you can use
           -e mon_to_kill=ceph-mon01 argument. You can only remove a single monitor each time the playbook runs."
      when: mon_to_kill is not defined

    - name: Exit playbook, if the monitor is not part of the inventory
      ansible.builtin.fail:
        msg: "It seems that the host given is not part of your inventory, please make sure it is."
      when: mon_to_kill not in groups[mon_group_name]

    - name: Exit playbook, if user did not mean to shrink cluster
      ansible.builtin.fail:
        msg: "Exiting shrink-mon playbook, no monitor was removed.
           To shrink the cluster, either say 'yes' on the prompt or
           or use `-e ireallymeanit=yes` on the command line when
           invoking the playbook"
      when: ireallymeanit != 'yes'

    - name: Import ceph-defaults role
      ansible.builtin.import_role:
        name: ceph-defaults

    - name: Import ceph-facts role
      ansible.builtin.import_role:
        name: ceph-facts
        tasks_from: container_binary

  tasks:
    - name: Pick a monitor different than the one we want to remove
      ansible.builtin.set_fact:
        mon_host: "{{ item }}"
      with_items: "{{ groups[mon_group_name] }}"
      when: item != mon_to_kill

    - name: Set container_exec_cmd fact
      ansible.builtin.set_fact:
        container_exec_cmd: "{{ container_binary }} exec ceph-mon-{{ hostvars[mon_host]['ansible_facts']['hostname'] }}"
      when: containerized_deployment | bool

    - name: Exit playbook, if can not connect to the cluster
      ansible.builtin.command: "{{ container_exec_cmd }} timeout 5 ceph --cluster {{ cluster }} health"
      register: ceph_health
      changed_when: false
      until: ceph_health.stdout.find("HEALTH") > -1
      delegate_to: "{{ mon_host }}"
      retries: 5
      delay: 2

    - name: Set_fact mon_to_kill_hostname
      ansible.builtin.set_fact:
        mon_to_kill_hostname: "{{ hostvars[mon_to_kill]['ansible_facts']['hostname'] }}"

    - name: Stop monitor service(s)
      ansible.builtin.service:
        name: ceph-mon@{{ mon_to_kill_hostname }}
        state: stopped
        enabled: false
      delegate_to: "{{ mon_to_kill }}"
      failed_when: false

    - name: Purge monitor store
      ansible.builtin.file:
        path: /var/lib/ceph/mon/{{ cluster }}-{{ mon_to_kill_hostname }}
        state: absent
      delegate_to: "{{ mon_to_kill }}"

    - name: Remove monitor from the quorum
      ansible.builtin.command: "{{ container_exec_cmd }} ceph --cluster {{ cluster }} mon remove {{ mon_to_kill_hostname }}"
      changed_when: false
      failed_when: false
      delegate_to: "{{ mon_host }}"

  post_tasks:
    - name: Verify the monitor is out of the cluster
      ansible.builtin.command: "{{ container_exec_cmd }} ceph --cluster {{ cluster }} quorum_status -f json"
      delegate_to: "{{ mon_host }}"
      changed_when: false
      failed_when: false
      register: result
      until: mon_to_kill_hostname not in (result.stdout | from_json)['quorum_names']
      retries: 2
      delay: 10

    - name: Please remove the monitor from your ceph configuration file
      ansible.builtin.debug:
        msg: "The monitor has been successfully removed from the cluster.
              Please remove the monitor entry from the rest of your ceph configuration files, cluster wide."
      run_once: true
      when: mon_to_kill_hostname not in (result.stdout | from_json)['quorum_names']

    - name: Fail if monitor is still part of the cluster
      ansible.builtin.fail:
        msg: "Monitor appears to still be part of the cluster, please check what happened."
      run_once: true
      when: mon_to_kill_hostname in (result.stdout | from_json)['quorum_names']

    - name: Show ceph health
      ansible.builtin.command: "{{ container_exec_cmd }} ceph --cluster {{ cluster }} -s"
      delegate_to: "{{ mon_host }}"
      changed_when: false

    - name: Show ceph mon status
      ansible.builtin.command: "{{ container_exec_cmd }} ceph --cluster {{ cluster }} mon stat"
      delegate_to: "{{ mon_host }}"
      changed_when: false