Renderers¶

Multiple Renderers¶

When deploying a state tree a default renderer is selected in the master configuration file with the renderer option. But multiple renderers can be used inside the same state tree.

When rendering SLS files Salt checks for the presence of a Salt specific shebang line. The shebang line syntax was chosen because it is familiar to the target audience, the systems admin and systems engineer.

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 in to use the Python or py renderer:

#!py

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

The first line is a shebang that references the py renderer.

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 combining a YAML renderer and a Jinja renderer. Such renderer configuration is specified as: jinja | yaml.

Other renderer combinations are possible, here's a few examples:

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.

And here's 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 as well.

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. Also, for example, it doesn't make sense to specify yaml | jinja either, 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.

Writing Renderers¶

Writing a renderer is easy, all that is required is that a Python module is placed in the rendered directory and that the module implements the render function. The render function will be passed the path of the SLS file. In the render function, parse the passed file and return the data structure derived from the file. You can place your custom renderers in a _renderers directory within the file_roots specified by the master config file. These custom renderers are distributed when state.highstate is run, or by executing the saltutil.sync_renderers or saltutil.sync_all functions.

Examples¶

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