Tag: play

Useful ansible stuff

inventory_hostname

‘inventory_hostname‘ contains the name of the current node being worked on…. (as in, what it is defined in your hosts file as) so if you want to skip a task for a single node –

- name: Restart amavis
  service: name=amavis state=restarted
  when: inventory_hostname != "boris"

(Don’t restart Amavis for boris,  do for all others).

You could also use :

...
  when: inventory_hostname not in groups['group_name']
...

if your aim was to (perhaps skip) a task for some nodes in the specified group.

 

Need to check whether you need to reboot for a kernel update?

  1. If /vmlinuz doesn’t resolve to the same kernel as we’re running
  2. Reboot
  3. Wait 45 seconds before carrying on…
- name: Check for reboot hint.
  shell: if [ $(readlink -f /vmlinuz) != /boot/vmlinuz-$(uname -r) ]; then echo 'reboot'; else echo 'no'; fi
  ignore_errors: true
  register: reboot_hint

- name: Rebooting ...
  command: shutdown -r now "Ansible kernel update applied"
  async: 0
  poll: 0
  ignore_errors: true
  when: kernelup|changed or reboot_hint.stdout.find("reboot") != -1
  register: rebooting

- name: Wait for thing to reboot...
  pause: seconds=45
  when: rebooting|changed

Fixing ~/.ssh/known_hosts

Often an ansible script may create a remote node – and often it’ll have the same IP/name as a previous entity. This confuses SSH — so after creating :

- name: Fix .ssh/known_hosts. (1)
  local_action: command  ssh-keygen -f "~/.ssh/known_hosts" -R hostname

If you’re using ec2, for instance, you could do something like :

- name: Fix .ssh/known_hosts.
  local_action: command  ssh-keygen -f "~/.ssh/known_hosts" -R {{ item.public_ip }} 
  with_items: ec2_info.instances

Where ec2_info is your registered variable from calling the ‘ec2’ module.

Debug/Dump a variable?

- name: What's in reboot_hint?
  debug: var=reboot_hint

which might output something like :

"reboot_hint": {
        "changed": true, 
        "cmd": "if [ $(readlink -f /vmlinuz) != /boot/vmlinuz-$(uname -r) ]; then echo 'reboot'; else echo 'no'; fi", 
        "delta": "0:00:00.024759", 
        "end": "2014-07-29 09:05:06.564505", 
        "invocation": {
            "module_args": "if [ $(readlink -f /vmlinuz) != /boot/vmlinuz-$(uname -r) ]; then echo 'reboot'; else echo 'no'; fi", 
            "module_name": "shell"
        }, 
        "rc": 0, 
        "start": "2014-07-29 09:05:06.539746", 
        "stderr": "", 
        "stdout": "reboot", 
        "stdout_lines": [
            "reboot"
        ]
    }

Which leads on to —

Want to run a shell command do something with the output?

Registered variables have useful attributes like :

  • changed – set to boolean true if something happened (useful to tell when a task has done something on a remote machine).
  • stderr – contains stringy output from stderr
  • stdout – contains stringy output from stdout
  • stdout_lines – contains a list of lines (i.e. stdout split on n).

(see above)

- name: Do something
  shell: /usr/bin/something | grep -c foo || true
  register: shell_output

So – we could :

- name: Catch some fish (there are at least 5)
  shell: /usr/bin/somethingelse 
  when: shell_output.stdout > "5"

Default values for a Variable, and host specific values.

Perhaps you’ll override a variable, or perhaps not … so you can do something like the following in a template :

...
max_allowed_packet = {{ mysql_max_allowed_packet|default('128M') }}
...

And for the annoying hosts that need a larger mysql_max_allowed_packet, just define it within the inventory hosts file like :

[linux_servers]
beech
busy-web-server mysql_max_allowed_packet=256M

Ansible issues

  1. is not a valid attribute for a Play
    When ever you get the above error firstly crosscheck that the ansible attribute you have mentioned is correct. If it is correct then the issue probably is that you have created tasks as follows:

    ---
   - vars_prompt:
        - name: "var1"
          prompt: "Please pass variable"
          private: no

   - fail: msg="var1 is not passed or blank"
     when: var1 is undefined or ( var1 is defined and storeid == "" )

    when it should be as follows:

    ---
   vars_prompt:
      - name: "var1"
        prompt: "Please pass variable"
        private: no

   tasks:
     - fail: msg="var1 is not passed or blank"
       when: var1 is undefined or ( var1 is defined and storeid == "" )

    the example referenced is just a task. It is not a valid playbook because it is missings a hosts declaration and the module call is not under a tasks section.

  2. ERROR! conflicting action statements: fail, command
    I get this error if I have a task as follows:
    – name: deploy
    win_get_url:
    url: ‘http://server_ip/builds/build.zip’
    dest: ‘D:build.zip’
    win_unzip:
    src: D:build.zip
    dest: D:You cannot have multiple actions listed inside a single task like this. Instead you need to do this:

        - name: deploy get url
      win_get_url:
         url: 'http://server_ip/builds/build.zip'
         dest: 'D:build.zip'
    - name: deploy unzip
      win_unzip:
         src: D:build.zip
         dest: D:
  3. Ansible task to check API status
    Here I am checking ES cluster health:

        - name: Get ES cluster health
      uri:
        url: http://{{inventory_hostname}}:9200/_cluster/health
        return_content: yes
      register: cluster_status

    - set_fact:
        es_cluster_health: "{{ cluster_status.content | from_json }}"

    - fail: msg="ES cluster not healthy"
      when: "es_cluster_health.status != 'yellow'"

    You can compare the status with any string you want. Here I am comparing it with string “yellow”