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

---
# This playbook removes the Ceph MDS from your cluster.
#
# Use it like this:
# ansible-playbook shrink-mds.yml -e mds_to_kill=ceph-mds01
#     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-mds.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') }}"
    - "{{ mds_group_name | default('mdss') }}"
  become: true
  tasks:
    - debug:
        msg: gather facts on all Ceph hosts for following reference

- name: perform checks, remove mds and print cluster health
  hosts: localhost
  become: true
  vars_prompt:
    - name: ireallymeanit
      prompt: Are you sure you want to shrink the cluster?
      default: 'no'
      private: no
  pre_tasks:
    - import_role:
        name: ceph-defaults

    - name: exit playbook, if no mds was given
      when: mds_to_kill is not defined
      fail:
        msg: >
          mds_to_kill must be declared.
          Exiting shrink-cluster playbook, no MDS was removed. On the command
          line when invoking the playbook, you can use
          "-e mds_to_kill=ceph-mds1" argument.  You can only remove a single
          MDS each time the playbook runs."

    - name: exit playbook, if the mds is not part of the inventory
      when: mds_to_kill not in groups[mds_group_name]
      fail:
        msg: "It seems that the host given is not part of your inventory,
              please make sure it is."

    - name: exit playbook, if user did not mean to shrink cluster
      when: ireallymeanit != 'yes'
      fail:
        msg: "Exiting shrink-mds playbook, no mds 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"

    - import_role:
        name: ceph-facts

    - name: set_fact container_exec_cmd for mon0
      set_fact:
        container_exec_cmd: >
          {{ container_binary }} exec ceph-mon-{{ hostvars[groups
          [mon_group_name][0]]['ansible_hostname'] }}
      when: containerized_deployment | bool

    - name: exit playbook, if can not connect to the cluster
      command: >
        {{ container_exec_cmd | default('') }} timeout 5 ceph --cluster
        {{ cluster }} health
      register: ceph_health
      until: ceph_health is succeeded
      delegate_to: "{{ groups[mon_group_name][0] }}"
      retries: 5
      delay: 2

    - name: set_fact mds_to_kill_hostname
      set_fact:
        mds_to_kill_hostname: "{{ hostvars[mds_to_kill]['ansible_hostname'] }}"

  tasks:
    - name: stop mds service(s)
      service:
        name: ceph-mds@{{ mds_to_kill_hostname }}
        state: stopped
        enabled: no
      delegate_to: "{{ mds_to_kill }}"
      failed_when: false

    - name: purge mds store
      file:
        path: /var/lib/ceph/mds/{{ cluster }}-{{ mds_to_kill_hostname }}
        state: absent
      delegate_to: "{{ mds_to_kill }}"

  post_tasks:
    - name: verify that the mds has stopped
      shell: >
        {{ container_exec_cmd | default('') }} ceph --cluster ceph --conf
        /etc/ceph/ceph.conf fs dump | grep mds0
      register: result
      failed_when: result.rc == 0
      delegate_to: "{{ mds_to_kill }}"

    - name: show ceph health
      command: >
        {{ container_exec_cmd | default('') }} ceph --cluster
        {{ cluster }} -s
      delegate_to: "{{ groups[mon_group_name][0] }}"