add_host and --limit

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1

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?

2

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.

3

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”.

4

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

śr., 5.06.2019, 09:12 użytkownik Kai Stian Olstad <ansible-project+list@olstad.com> napisał:

5

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