haproxy_drain_backend.yml

---

# Run like: haproxy_drain_backend.yml --extra-vars="webserver=web01"

- hosts: haproxys
  serial: 1
  gather_facts: true
  max_fail_percentage: 0
  become: true
  vars:
    haproxy_backend: mybackend
    haproxy_ready_state: UP
    haproxy_draining_state: DRAIN
    haproxy_maintenance_state: MAINT
    haproxy_mode_check_wait: 5 # seconds (ensure all checks are done)
    haproxy_mode_change_wait: 15 # seconds
    haproxy_socket_location: /var/run/haproxy.sock
  tasks:
    - name: sanity check
      fail:
        msg: "Variable {{ item }} is not defined!"
      when: "{{ item }} is not defined"
      with_items:
        - haproxy_backend
        - haproxy_mode_check_wait
        - haproxy_mode_change_wait
        - haproxy_ready_state
        - haproxy_draining_state
        - haproxy_maintenance_state
        - haproxy_socket_location
        - webserver

    - name: doing what
      debug:
        msg: "Changing {{ haproxy_backend }}/{{ webserver }} to MAINT state on {{ ansible_nodename }} .."

    - name: obtain current backend state (UP, DRAIN, MAINT)
      shell: "echo \"show stat\" | socat {{ haproxy_socket_location }} stdio | grep {{ haproxy_backend }},{{ webserver }} | awk -F ',' '{print $18}'"
      changed_when: false
      register: backend_pre_state

    - name: initial status
      debug:
        msg: "{{ backend_pre_state.stdout }}"

    - name: put backend in Draining
      shell: "echo \"set server {{ haproxy_backend }}/{{ webserver }} state drain\" | socat stdio {{ haproxy_socket_location }}"
      register: drain_output
      when: '"{{ haproxy_ready_state }}" in backend_pre_state.stdout'

#    - name: output of drain action
#      debug:
#        msg: "{{ drain_output | to_nice_json }}"
#      when: drain_output | changed

    - name: wait for state change
      pause:
        seconds: "{{ haproxy_mode_check_wait }}"
      when: drain_output | changed

    - name: obtain current backend state (UP, DRAIN, MAINT)
      shell: "echo \"show stat\" | socat {{ haproxy_socket_location }} stdio | grep {{ haproxy_backend }},{{ webserver }} | awk -F ',' '{print $18}'"
      changed_when: false
      failed_when: 'backend_post_drain_state.stdout == "{{ haproxy_ready_state }}"'
      when: drain_output | changed
      register: backend_post_drain_state

    - name: current state
      debug:
        msg: "{{ backend_post_drain_state.stdout }}"
      when: backend_post_drain_state.stdout is defined

    - name: wait for mode change
      pause:
        seconds: "{{ haproxy_mode_change_wait }}"
      when: backend_post_drain_state.stdout is defined

    - name: put backend in Maintenance
      shell: "echo \"disable server {{ haproxy_backend }}/{{ webserver }}\" | socat stdio {{ haproxy_socket_location }}"
      register: maintenance_output
      when: haproxy_maintenance_state != backend_pre_state.stdout

#    - name: output of maintenance action
#      debug:
#        msg: "{{ maintenance_output | to_nice_json }}"
#      when: maintenance_output | changed

    - name: wait for state to change
      pause:
        seconds: "{{ haproxy_mode_check_wait }}"
      when: maintenance_output | changed

    - name: obtain current backend state (UP, DRAIN, MAINT)
      shell: "echo \"show stat\" | socat {{ haproxy_socket_location }} stdio | grep {{ haproxy_backend }},{{ webserver }} | awk -F ',' '{print $18}'"
      changed_when: false
      failed_when: 'backend_post_maintenance_state.stdout != "{{ haproxy_maintenance_state }}"'
      when: maintenance_output | changed
      register: backend_post_maintenance_state

    - name: current state
      debug:
        msg: "{{ backend_post_maintenance_state.stdout }}"
      when: backend_post_maintenance_state.stdout is defined