Is there a way to dynamically target subsets of an inventory group based on facts?

[Willard Dennis]

Hi all,

I have an inventory file with hosts in different groups within. I would like to run a playbook on a certain group, but only where the host members of that group that have a certain OS (say, " ansible_distribution='Fedora' ".) I was told to look at the "group_by" module, and so in my top-level site.yml file I put in the following:

# Set up OS-specific groups
- group_by: key=os-{{ansible_distribution}}

So then I tried to do the following:

$ ansible-playbook -i inventory-file -u root -k site.yml --tags=mailserver --limit=os-Fedora

but when I do so, I get:

ERROR: provided hosts list is empty

So am I doing this incorrectly, or for some reason, is the "os-Fedora" group empty? (i.e. the logic is not matching any hosts)

Also, is there a way to print the members of the group_by variable out so I can see what's being included?

Thanks,
Will

[Serge van Ginderachter]

On 12 September 2014 16:48, Willard Dennis <willard...@gmail.com> wrote:

So am I doing this incorrectly, or for some reason, is the "os-Fedora" group empty? (i.e. the logic is not matching any hosts)

​The --limit happens early, at initialization​, and at that time the group is indeed empty.

AFAIK, there is no workaround for this.

[Michael DeHaan]

You can't use group_by stuff at that point because it hasn't run yet, true, but there is a solution to what you would like to do, using two plays in the same playbook

- hosts: all

  tasks:

     - group_by: key=os-{{ ansible_distribution }}

- hosts: "{{ distro | default('all') }}"

  tasks:

     - action: ping

     - ...

ansible-playbook foo.yml -e "pattern=os-Fedora"

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[Michael DeHaan]

Sorry in the above, the word "distro" should be "pattern".

[Willard Dennis]

Thanks, Michael! But can I do the following?

$ cat site.yml
---

- hosts: all
  tasks:

# Set up OS-specific groups

  - group_by: key=os-{{ansible_distribution}}-{{ansible_distribution_version}}

- hosts: "{{ distro | default('all') }}"

  include:
  - dept1-servers.yml
  - dept2-servers.yml
  - base-static-setup.yml


Rather not change the individual playbooks if I can help it.

Thanks,
Will

[Willard Dennis]

Hmmm, I guess not...

$ ansible-playbook -i temp-stor-inv -u root -k site.yml --tags=mailserver -e "distro=os-Fedora-20"
SSH password:
Traceback (most recent call last):
  File "/usr/bin/ansible-playbook", line 309, in <module>
    sys.exit(main(sys.argv[1:]))
  File "/usr/bin/ansible-playbook", line 191, in main
    force_handlers=options.force_handlers
  File "/usr/lib/pymodules/python2.7/ansible/playbook/__init__.py", line 180, in __init__
    (self.playbook, self.play_basedirs) = self._load_playbook_from_file(playbook, vars)
  File "/usr/lib/pymodules/python2.7/ansible/playbook/__init__.py", line 271, in _load_playbook_from_file
    inc_vars, inc_path = self._get_include_info(play, basedir, play_vars)
  File "/usr/lib/pymodules/python2.7/ansible/playbook/__init__.py", line 208, in _get_include_info
    tokens = shlex.split(play_ds.get('include', ''))
  File "/usr/lib/python2.7/shlex.py", line 279, in split
    return list(lex)
  File "/usr/lib/python2.7/shlex.py", line 269, in next
    token = self.get_token()
  File "/usr/lib/python2.7/shlex.py", line 96, in get_token
    raw = self.read_token()
  File "/usr/lib/python2.7/shlex.py", line 124, in read_token
    nextchar = self.instream.read(1)
AttributeError: 'list' object has no attribute 'read'

[Michael DeHaan]

I'm unclear what you meant by "can I do X" specifically, what that meant you could or couldn't do.

A traceback in ansible is a bug though, so please figure out what the minimum way to reproduce that is and file a ticket (provided you are using at least 1.7.1 already and it can be reproduced there).

If you can, checking the devel branch would also be useful.

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[Willard Dennis]

Sorry Michael, I will try to be more clear.

I am running Ansible 1.7.1 currently.

So my original site.yml is this:

$ cat site.yml.orig
---

- include: dept1-servers.yml
- include: dept2-servers.yml
- include: base-static-setup.yml

...which works fine.

The one producing the traceback is this:

$ cat site.yml.bad

---

- hosts: all
  tasks:
# Set up OS-specific groups
  - group_by: key=os-{{ansible_distribution}}-{{ansible_distribution_version}}

- hosts: "{{ distro | default('all') }}"
  include:
  - dept1-servers.yml
  - dept2-servers.yml
  - base-static-setup.yml

I also tested the following:

$ cat site.yml.test1

---
- hosts: all
  tasks:
# Set up OS-specific groups
  - group_by: key=os-{{ansible_distribution}}-{{ansible_distribution_version}}

- include: am-servers.yml
- include: stor-servers.yml
- include: base-static-setup.yml

Which ran fine as well, so it must be the following block that is causing the fault:

- hosts: "{{ distro | default('all') }}"
  include:
  - dept1-servers.yml
  - dept2-servers.yml
  - base-static-setup.yml

All I am trying to do is to make the included playbooks run only for machines with the specified OS, if I specify the target OS on the ansible-playbook command line via the ' -e "distro=os-Fedora-20"' variable construct you gave me. That way I can always target a subset of my specified inventory by OS, if I want to run certain plays (say those with a specific tag) only against member servers with the specified OS. Otherwise, if I don't pass an " -e distro=<whatever>" variable, it will target all members of the inventory. Make sense?

- Will