Change a global var in a task

[Petros Moisiadis]

Is there any way to change a global variable (e.g. defined in the vars
section of a playbook) in a task for the current playbook run?

The use case is that I want to start with a boolean variable set to
True, and then run a command over a set of hosts. If a command at _any_
of the hosts returns a specific value in stdout, I want to set the
global boolean variable to False. This 'control' boolean variable will
be checked later to decide where to run (or not run) some other tasks,
so what I want actually is to create a conditional based on output from
multiple tasks or multiple runs in a task loop . I know about the
'set_fact' module, but this works on a per-host basis, not on global
vars, so it does not help. Perhaps, I need a 'set_var' or 'set_global'
module or something like that. I can think of some hacky ways to
workaround my case (e.g. use a temporary file instead of a global var),
but I think changing the value of a global var at will in the course of
a playbook run should be something that Ansible should allow us to do.
Am I missing something here?

[James Cammarata]

Using set_fact should still achieve the same effect, you're using that variable over multiple plays with differing sets of hosts?

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[Petros Moisiadis]

On 05/15/14 16:17, James Cammarata wrote:

Using set_fact should still achieve the same effect, you're using that variable over multiple plays with differing sets of hosts?

Hmm... I see your point. It can be done by looping over the results of the previous task (which should run on all hosts) and run set_fact which will eventually set the same boolean value for all hosts. Thanks.

However, I am thinking if a 'set_global' would be useful in other, more complicated cases. Perhaps, this is why you ask about different sets of hosts. I have a feeling that in such cases the 'per-host' nature of set_fact could become inconvenient. Also, it comes natural to me that setting and changing a var globally (for all hosts) in a single pass would be something possible.

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[James Cammarata]

It might be useful, if you're interested in writing/contributing something like that we'd definitely consider it.

Thanks!

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[Petros Moisiadis]

On 05/15/14 17:27, 'Petros Moisiadis' via Ansible Project wrote:

On 05/15/14 16:17, James Cammarata wrote:

Using set_fact should still achieve the same effect, you're using that variable over multiple plays with differing sets of hosts?

Hmm... I see your point. It can be done by looping over the results of the previous task (which should run on all hosts) and run set_fact which will eventually set the same boolean value for all hosts. Thanks.

Unfortunately this does not work. set_fact does not override variables defined in "vars" section.
I used the following playbook to test it:

---
- hosts: localhost
  user: root
  vars:
    test: 1
  tasks:
    - name: set test
      set_fact: test=2

    - name: debug
      debug: msg="{{ test }}"


The output:

PLAY [localhost] **************************************************************

GATHERING FACTS ***************************************************************
ok: [localhost]

TASK: [set test] **************************************************************
ok: [localhost] => {"ansible_facts": {"test": "2"}}

TASK: [debug] *****************************************************************
ok: [localhost] => {
    "msg": "1"
}

PLAY RECAP ********************************************************************
localhost                  : ok=3    changed=0    unreachable=0    failed=0  


As you see, although set_fact sets test to "2",  the debug task prints "1". I am not sure if this is a bug or not, but it surely destroys a possible workaround.

[Michael DeHaan]

This is due to a (intentional) change in 1.6, to make sure variables from hosts that are tampered with don't influence variables that describe whether or not a specific configuration is applied to them.

Thus we would need a "set_global" type action plugin (which would also need to be "bypass host loop" in order to be functional).  

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[Michael DeHaan]

Minor correction, change was made in the 1.5 updates.