21.21. Renderers

The Salt state system operates by gathering information from common data types such as lists, dictionaries and strings that would be familiar to any developer.

SLS files are translated from whatever data templating format they are written in back into Python data types to be consumed by Salt.

By default SLS files are rendered as Jinja templates and then parsed as YAML documents. But since the only thing the state system cares about is raw data, the SLS files can be any structured format that can be dreamed up.

Currently there is support for Jinja + YAML, Mako + YAML, Wempy + YAML, Jinja + json, Mako + json and Wempy + json.

Renderers can be written to support any template type. This means that the Salt states could be managed by XML files, HTML files, Puppet files, or any format that can be translated into the Pythonic data structure used by the state system.

21.21.1. Multiple Renderers

A default renderer is selected in the master configuration file by providing a value to the renderer key.

When evaluating an SLS, more than one renderer can be used.

When rendering SLS files, Salt checks for the presence of a Salt-specific shebang line.

The shebang line directly calls the name of the renderer as it is specified within Salt. One of the most common reasons to use multiple renderers is to use the Python or py renderer.

Below, the first line is a shebang that references the py renderer.

#!py

def run():
    '''
    Install the python-mako package
    '''
    return {'include': ['python'],
            'python-mako': {'pkg': ['installed']}}

21.21.2. Composing Renderers

A renderer can be composed from other renderers by connecting them in a series of pipes(|).

In fact, the default Jinja + YAML renderer is implemented by connecting a YAML renderer to a Jinja renderer. Such renderer configuration is specified as: jinja | yaml.

Other renderer combinations are possible:

yaml
i.e, just YAML, no templating.
mako | yaml
pass the input to the mako renderer, whose output is then fed into the yaml renderer.
jinja | mako | yaml
This one allows you to use both jinja and mako templating syntax in the input and then parse the final rendered output as YAML.

The following is a contrived example SLS file using the jinja | mako | yaml renderer:

#!jinja|mako|yaml

An_Example:
  cmd.run:
    - name: |
        echo "Using Salt ${grains['saltversion']}" \
             "from path {{grains['saltpath']}}."
    - cwd: /

<%doc> ${...} is Mako's notation, and so is this comment. </%doc>
{#     Similarly, {{...}} is Jinja's notation, and so is this comment. #}

For backward compatibility, jinja | yaml can also be written as yaml_jinja, and similarly, the yaml_mako, yaml_wempy, json_jinja, json_mako, and json_wempy renderers are all supported.

Keep in mind that not all renderers can be used alone or with any other renderers. For example, the template renderers shouldn't be used alone as their outputs are just strings, which still need to be parsed by another renderer to turn them into highstate data structures.

For example, it doesn't make sense to specify yaml | jinja because the output of the YAML renderer is a highstate data structure (a dict in Python), which cannot be used as the input to a template renderer. Therefore, when combining renderers, you should know what each renderer accepts as input and what it returns as output.

21.21.3. Writing Renderers

A custom renderer must be a Python module placed in the rendered directory and the module implement the render function.

The render function will be passed the path of the SLS file as an argument.

The purpose of of render function is to parse the passed file and to return the Python data structure derived from the file.

Custom renderers must be placed in a _renderers directory within the file_roots specified by the master config file.

Custom renderers are distributed when any of the following are run:

state.highstate

saltutil.sync_renderers

saltutil.sync_all

Any custom renderers which have been synced to a minion, that are named the same as one of Salt's default set of renderers, will take the place of the default renderer with the same name.

21.21.4. Examples

The best place to find examples of renderers is in the Salt source code.

Documentation for renderers included with Salt can be found here:

https://github.com/saltstack/salt/blob/develop/salt/renderers

Here is a simple YAML renderer example:

import yaml
def render(yaml_data, env='', sls='', **kws):
    if not isinstance(yaml_data, basestring):
        yaml_data = yaml_data.read()
    data = yaml.load(yaml_data)
    return data if data else {}

These docs are for Salt's development version: 014bcc5.

Docs for previous releases are available on salt.rtfd.org.

Latest Salt release: 2014.1.3

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