Reboot system with Ansible and wait of it to come back

reboot.yml

- hosts: all                                                                                                                                                                                                       
  become: yes                                                                                                                                                                                                      
  gather_facts: no                                                                                                                                                                                                 
  remote_user: cloud-user                                                                                                                                                                                          
  tasks:                                                                                                                                                                                                           
    - name: "Reboot system"                                                                                                                                                                                        
      shell: sleep 5 && /usr/sbin/reboot                                                                                                                                                                           
      async: 1                                                                                                                                                                                                     
      poll: 0                                                                                                                                                                                                      
                                                                                                                                                                                                                   
    - name: "Wait for server to finish reboot"                                                                                                                                                                     
      wait_for_connection:                                                                                                                                                                                         
        timeout: 120                                                                                                                                                                                               
        delay: 10

With the reboot module available since Ansible 2.7 things become easier :-)

Ad an ad-hoc command

$ ansible -m reboot -i <inventory> all

or in a playbook

- hosts: all
  become: yes
  tasks:
    - name: Rebooting nodes
      reboot:
        reboot_timeout: 3600