On 23.05.2014 14:29, Michael DeHaan wrote:
I'm unclear on why we need a variable to indicate whether we are in check
mode when always_run can be used for data gathering commands.
It's not a workaround, it's a feature :)
Right, a variable like that wouldn't make anything new possible, it's just that I recall I wanted it for something. I'll note any use-cases if I run into them again (my memory is not too good with things I had gotten around anyway...).


On Thu, May 22, 2014 at 1:20 PM, Tomasz Kontusz <[email protected]>wrote:

On 22.05.2014 17:20, Marc Petrivelli wrote:

Variables that are brought into scope through the "register: var" when a
task is executed are not available when a playbook is run with the --check
mode.

That depends on the task - if a given module supports check-mode (most of
the ones bundled with Ansible do) it will give you *some* information.
Tasks using modules that do not support check mode are skipped by default,
so you'd need a workaround

  The work-around I have been using is to put defaults (for all those
variables that will eventually be brought into scope using register) using
set_fact or group_vars/all or an included var file.

One way to work around it for modules that don't support check mode (like
command/shell, which can't do it for obvious reasons :-)) is to have a
data-gathering command with "always_run: yes", and then use that to decide
if the target command should be run.

For example:
- name: Get Jenkins's plugins
   shell: jenkins-cli -s {{ jenkins.url }} list-plugins | cut -f 1 -d ' '
   register: installed_plugins
   changed_when: False
   always_run: yes  # This gets run even in check mode, as it's safe to
read a list of plugins

- name: Install missing plugins
   shell: jenkins-cli -s {{ jenkins.url }} install-plugin -deploy {{ item }}
   with_items: jenkins.plugins
   when: item not in installed_plugins.stdout_lines


  I suggest changing the ansible --check mode to not evaluate those
variables, in the when clause, normally brought into scope using register.

That sounds like a pretty confusing behavior, and it would break a lot of
existing plays.


  Does anyone else have this problem?  Did you use another work around? Do
you like my idea of selectively evaluating variables that are
"registered"?

  I did have this problem, and I still would sometimes like to have a
variable telling me if I'm in check mode (I know I can create one with
set_fact and always_run, but it's an ugly hack).
The only real workaround that won't make your --check runs useless is
splitting tasks into probing the system part, and changing the system part
(or writing modules that do this :-)).


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