linux - How to wait for server restart using Ansible?

Question

I'm trying to restart the server and then wait, using this:

- name: Restart server
  shell: reboot

- name: Wait for server to restart
  wait_for:
    port=22
    delay=1
    timeout=300

But I get this error:

TASK: [iptables | Wait for server to restart] ********************************* 
fatal: [example.com] => failed to transfer file to /root/.ansible/tmp/ansible-tmp-1401138291.69-222045017562709/wait_for:
sftp> put /tmp/tmpApPR8k /root/.ansible/tmp/ansible-tmp-1401138291.69-222045017562709/wait_for

Connected to example.com.
Connection closed

Answer 1

Ansible >= 2.7 (released in Oct 2018)

Use the built-in reboot module:

- name: Wait for server to restart
  reboot:
    reboot_timeout: 3600

Ansible < 2.7

Restart as a task

- name: restart server
  shell: 'sleep 1 && shutdown -r now "Reboot triggered by Ansible" && sleep 1'
  async: 1
  poll: 0
  become: true

This runs the shell command as an asynchronous task, so Ansible will not wait for end of the command. Usually async param gives maximum time for the task but as poll is set to 0, Ansible will never poll if the command has finished - it will make this command a "fire and forget". Sleeps before and after shutdown are to prevent breaking the SSH connection during restart while Ansible is still connected to your remote host.

Wait as a task

You could just use:

- name: Wait for server to restart
  local_action:
    module: wait_for
      host={{ inventory_hostname }}
      port=22
      delay=10
    become: false

..but you may prefer to use {{ ansible_ssh_host }} variable as the hostname and/or {{ ansible_ssh_port }} as the SSH host and port if you use entries like:

hostname         ansible_ssh_host=some.other.name.com ansible_ssh_port=2222 

..in your inventory (Ansible hosts file).

This will run the wait_for task on the machine running Ansible. This task will wait for port 22 to become open on your remote host, starting after 10 seconds delay.

Restart and wait as handlers

But I suggest to use both of these as handlers, not tasks.

There are 2 main reason to do this:

• code reuse - you can use a handler for many tasks. Example: trigger server restart after changing the timezone and after changing the kernel,

• trigger only once - if you use a handler for a few tasks, and more than 1 of them will make some change => trigger the handler, then the thing that handler does will happen only once. Example: if you have a httpd restart handler attached to httpd config change and SSL certificate update, then in case both config and SSL certificate changes httpd will be restarted only once.

Read more about handlers here.

Restarting and waiting for the restart as handlers:

  handlers:

    - name: Restart server
      command: 'sleep 1 && shutdown -r now "Reboot triggered by Ansible" && sleep 1'
      async: 1
      poll: 0
      ignore_errors: true
      become: true

    - name: Wait for server to restart
      local_action:
        module: wait_for
          host={{ inventory_hostname }}
          port=22
          delay=10
        become: false

..and use it in your task in a sequence, like this, here paired with rebooting the server handler:

  tasks:
    - name: Set hostname
        hostname: name=somename
        notify:
          - Restart server
          - Wait for server to restart

Note that handlers are run in the order they are defined, not the order they are listed in notify!