SaltStack State Files Written In Python

Generally in SaltStack, state file are written in the YAML + Jinja2 format. However, other options are available. One of these options is Python.

In this post, we will display how a simple state written in YAML + Jinja2 can be written in Python instead. In the example, the function of the state is to take data in a pillar, and serialize it as YAML into a file.

The pillar data used in this example is:

breakfast:
  egg: scrambled
  meats:
    - sausage
    - bacon
  sides:
    spam: gross
    beans: baked

dinner:
  egg: poached
  seafood: lobster
  other:
    - truffle pate
    - mornay sauce
  sides:
    spam: delicious
    egg: over easy
  meats:
    - steak

The Salt State as written in YAML + Jinja2:

{% set application_pillar = ['breakfast', 'dinner'] %}

{%- for app_pillar in application_pillar %}
serialize key {  }:
  file.serialize:
    - name: /tmp/serialize_test.txt
    - user: root
    - group: root
    - mode: 400
    - formatter: yaml
    - dataset_pillar: {{ app_pillar }}
    - merge_if_exists: True
{% endfor %}

The Salt State as written in Python:

#!py

def _get_data():
    keys = ['breakfast', 'dinner']
    return keys

def run():
    config = {}

    for key in _get_data():
        config['serialize key '.format(key)] = {
            'file.serialize': [
                {'name': '/tmp/serialize_test.txt'},
                {'user': 'root'},
                {'group': 'root'},
                {'mode': '400'},
                {'formatter': 'yaml'},
                {'dataset_pillar': key}
            ]
        }

    return config

A few notes on the python version.

• The function name run is required.
• The run function must return a dictionary.
• The shebang, must be !py

Bonus

In SaltStack, the shebang really just specifies the order of renderers to use for the particular file. By default, the shebang is #!jinja|yaml

So… does that mean it’s possible to do #!jinja|py? Well, it seems like it should be, but I had no luck actually getting this to work. The jinja renderer would output what looked like a clean python file but then the py renderer would choke and spit out a syntax error due to a jinja line. For reference, I'll leave the code that was used. Maybe this is a bug that will get patched at some point.

#!jinja|py

{% set application_pillar = ['breakfast', 'dinner'] %}
def run():
 config = {}

{% for key in application_pillar %}
 config['serialize key {  }'] = {
  'file.serialize': [
   {'name': '/tmp/serialize_test.txt'},
   {'user': 'root'},
   {'group': 'root'},
   {'mode': '400'},
   {'formatter': 'yaml'},
   {'dataset_pillar': '{  }' }
  ]
 }
{% endfor %}

 return config

Update

I reached out to the salt community and was informed that any render pipelines that includes #!py only get evaluated with the py renderer. So that answers that.

Bonus Bonus

So… what about json?

Well if you’re a psychopath hell bent on squeezing out all the speed possible…yes

#!jinja|json

{% set application_pillar = ['breakfast', 'dinner'] %}
{
{%- for app_pillar in application_pillar %}
  "serialize key {  }": {
    "file.serialize": [
      {"name": "/tmp/serialize_test.txt"},
      {"user": "root"},
      {"group": "root"},
      {"mode": 400},
      {"formatter": "yaml"},
      {"dataset_pillar": "{  }" },
      {"merge_if_exists": "True"}
    ]
  }{% if not loop.last %},{% endif %}
{%- endfor %}
}

All render times are taken from the Salt Minion which is running as a single core vagrant instance on my laptop. YMMV.

jinja|yaml render time: 0.00130581855774

py render time: 0.000488996505737

jinja|json render time: 5.69820404053e-05 or 0.0000569

Generally, render time doesn’t really matter, but if you have a use case where it might, json is clearly what you're going to want to use.

Originally published at https://smartaleksolutions.com on September 15, 2020.