add_host and --limit

[Piotr Owcarz]

Hello All

I have the following inventory:

...

[group1]

host1

[group2]

host2

[all]

host1

host2

...

and a playbook:

- name: play1

  hosts: group1

  tasks:

    - add_host:

        name: "{{groups[group2] | first}}"

        groups: temp_group

    - debug: var=groups.temp_group

- name: play2

  hosts: temp_group

  tasks:

    - debug: msg="yay"

My intention is to execute a play on host1, where I read a host on which next play is going to be executed, and execute the second play on that host, but when I execute the playbook with --limit group1 even though the host2 is added to temp_group, ansible won't match any hosts to run the second play on. The output (writing from top of my head) :

$ ansible-playbook playbook.yml --limit group1

PLAY [play1] ***************

TASK [add_host] ************

ok: [host1]

TASK [debug] ***************

ok: [host1] => {

  "groups.temp_group" : [

     "host2"

  ]

}

PLAY [play2] ***************

skipping: no hosts matched

Is there any way to make the add_host work with --limit?

Thanks
Piotr

[Kai Stian Olstad]

The whole point with limit is to say, only run on this/these host(s), so
no unless you add that host to the limit statement.

Since you only have one host in group1 limit is not needed.

--
Kai Stian Olstad

[Knut Karevoll]

Firstly you should have a look at the delegate_to which might be a better way at achieving what you want. But I am assuming there is a good reason for your current approach. The reason it does not work is that the limit is still in place after you have done an add_host. So when it gets to the second play it see that there are no hosts both in temp_group and group1 and will therefore not do anything. One solution is to add temp_group to your limit. So you would run "ansible-playbook playbook.yml --limit group1:temp_group".

[Piotr Owcarz]

Thanks Kai,

I solved this with delegate_to, fortunately it was only a few simple tasks to execute on host2.

Out of curiousity, where does Ansible runtime keep the set of hosts which are the subject of a playbook, after being --limit-ed? Is it accesible from inside a playbook? Would a custom module have the access there?

Piotr

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[Kai Stian Olstad]

On 05.06.2019 09:58, Piotr Owcarz wrote:
> Out of curiousity, where does Ansible runtime keep the set of hosts
> which
> are the subject of a playbook, after being --limit-ed?

Ansible has a list of special variables and the one that gives you that
information is ansible_play_hosts_all.

For all of them check this page
https://docs.ansible.com/ansible/latest/reference_appendices/special_variables.html

--
Kai Stian Olstad