SaltStack file.recurse per minion

Question

Goal

How can I install files with file.recurse on the minion which are specific to minions?

Current Strategy

This would works:

   files_per_minion:
      file.recurse:
        - source: salt://monitoring/files/per_minion/{{ grains.id }}
        - name: /
        - template: jinja

... but it fails for minions which don't have this directory on the master. I don't want to create a directory for every minion on my master.

I search for a way for an optional include. Here is a condition in pseudo code:

 {% if magic_way_to_check_if_source_exists salt://monitoring/files/per_minion/{{ grains.id }} %}

   files_per_minion:
      file.recurse:
        - source: salt://monitoring/files/per_minion/{{ grains.id }}
        - name: /
        - template: jinja

 {% endif %}

Question

How to write the condition magic_way_to_check_if_source_exists ?

Other solutions welcome

The condition magic_way_to_check_if_source_exists is just one strategy to get to the goal. Other solutions are welcome.

Use Case

Imagine I want cron_tab_file_for_xhost to get installed, but only on the host called xhost. I could solve this by creating a directory tree and a file for this host like this:

monitoring/files/per_minion/xhost/etc/cron.d/cron_tab_file_for_xhost

Answer 1

There are different ways depending on your use cases and state tree.

The easiest one is to create a separate state and attach this using top.sls.

If you work on formulas, which are configured through pillar. I would write this information somewhere in my pillar. The states then decide based on the pillar data.

pillar.example:

yourformula:
  getspecificfile: true

somestate.sls:

{% if salt['pillar.get']("yourformula:getspecificfile") %}
files_per_minion:
  file.recurse:
    - source: salt://monitoring/files/per_minion/{{ grains.id }}
    - name: /
    - template: jinja
{% endif %}

UPDATE:

i just had a look in the docs of the file.managed state

The source parameter can be specified as a list. If this is done, then the first file to be matched will be the one that is used. This allows you to have a default file on which to fall back if the desired file does not exist on the salt fileserver. Here's an example:

/etc/foo.conf:
  file.managed:
    - source:
      - salt://foo.conf.{{ grains['fqdn'] }}
      - salt://foo.conf.fallback
    - user: foo
    - group: users
    - mode: 644
    - backup: minion

This seems to be another option - if you don't care to roll out empty files which are not necessary on your minions.