salt.pillar.makostack

Simple and flexible YAML ext_pillar which can read pillar from within pillar.

New in version 2016.3.0.

This custom saltstack ext_pillar is a direct ripoff of the 'stack' ext_pillar, simply ported to use mako instead of jinja2 for templating.

It supports the following features:

multiple config files that are mako templates with support for pillar, __grains__, __salt__, __opts__ objects.
a config file renders as an ordered list of files. Unless absolute, the paths of these files are relative to the current config file - if absolute, they will be treated literally.
this list of files are read in order as mako templates with support for stack, pillar, __grains__, __salt__, __opts__ objects.
all these rendered files are then parsed as yaml.
then all yaml dicts are merged in order, with support for the following. merging strategies: merge-first, merge-last, remove, and overwrite.
stack config files can be matched based on pillar, grains, or opts values, which make it possible to support kind of self-contained environments.

Configuration in Salt

Like any other external pillar, its configuration takes place through the ext_pillar key in the master config file.

However, you can configure MakoStack in 3 different ways:

Single config file

This is the simplest option, you just need to set the path to your single MakoStack config file like below:

ext_pillar:
  - makostack: /path/to/stack.cfg

List of config files

You can also provide a list of config files:

ext_pillar:
  - makostack:
      - /path/to/stack1.cfg
      - /path/to/stack2.cfg

Select config files through grains|pillar|opts matching

You can also opt for a much more flexible configuration: MakoStack allows one to select the config files for the current minion based on matching values from either grains, or pillar, or opts objects.

Here is an example of such a configuration, which should speak by itself:

ext_pillar:
  - makostack:
      pillar:environment:
        dev: /path/to/dev/stack.cfg
        prod: /path/to/prod/stack.cfg
      grains:custom:grain:
        value:
          - /path/to/stack1.cfg
          - /path/to/stack2.cfg
      opts:custom:opt:
        value: /path/to/stack0.cfg

Grafting data from files to arbitrary namespaces

An extended syntax for config files permits defining "graft points" on a per-config-file basis. As an example, if the file foo.cfg would produce the following:

foo:
  - bar
  - baz

and you specified the cfg file as /path/to/foo.cfg:yummy:fur, the following would actually end up in pillar after all merging was complete:

yummy:
  fur:
    foo:
      - bar
      - baz

MakoStack configuration files

The config files that are referenced in the above ext_pillar configuration are mako templates which must render as a simple ordered list of yaml files that will then be merged to build pillar data.

Unless an absolute path name is specified, the path of these yaml files is assumed to be relative to the directory containing the MakoStack config file. If a path begins with '/', however, it will be treated literally and can be anywhere on the filesystem.

The following variables are available in mako templating of makostack configuration files:

pillar: the pillar data (as passed by Salt to our ext_pillar function)
minion_id: the minion id ;-)
__opts__: a dictionary of mostly Salt configuration options
__grains__: a dictionary of the grains of the minion making this pillar call
__salt__: a dictionary of Salt module functions, useful so you don't have to duplicate functions that already exist (note: runs on the master)

So you can use all the power of mako to build your list of yaml files that will be merged in pillar data.

For example, you could have a MakoStack config file which looks like:

$ cat /path/to/stack/config.cfg
core.yml
osarchs/%{ __grains__['osarch'] }}.yml
oscodenames/%{ __grains__['oscodename'] }.yml
% for role in pillar.get('roles', []):
roles/%{ role }.yml
% endfor
minions/%{ minion_id }.yml

And the whole directory structure could look like:

$ tree /path/to/stack/
/path/to/stack/
├── config.cfg
├── core.yml
├── osarchs/
│   ├── amd64.yml
│   └── armhf.yml
├── oscodenames/
│   ├── wheezy.yml
│   └── jessie.yml
├── roles/
│   ├── web.yml
│   └── db.yml
└── minions/
    ├── test-1-dev.yml
    └── test-2-dev.yml

Overall process

In the above MakoStack configuration, given that test-1-dev minion is an amd64 platform running Debian Jessie, and which pillar roles is ["db"], the following yaml files would be merged in order:

core.yml
osarchs/amd64.yml
oscodenames/jessie.yml
roles/db.yml
minions/test-1-dev.yml

Before merging, every files above will be preprocessed as mako templates. The following variables are available in mako templating of yaml files:

stack: the MakoStack pillar data object that has currently been merged (data from previous yaml files in MakoStack configuration)
pillar: the pillar data (as passed by Salt to our ext_pillar function)
minion_id: the minion id ;-)
__opts__: a dictionary of mostly Salt configuration options
__grains__: a dictionary of the grains of the minion making this pillar call
__salt__: a dictionary of Salt module functions, useful so you don't have to duplicate functions that already exist (note: runs on the master)

So you can use all the power of mako to build your pillar data, and even use other pillar values that has already been merged by MakoStack (from previous yaml files in MakoStack configuration) through the stack variable.

Once a yaml file has been preprocessed by mako, we obtain a Python dict - let's call it yml_data - then, MakoStack will merge this yml_data dict in the main stack dict (which contains already merged MakoStack pillar data). By default, MakoStack will deeply merge yml_data in stack (similarly to the recurse salt pillar_source_merging_strategy), but 3 merging strategies are currently available for you to choose (see next section).

Once every yaml files have been processed, the stack dict will contain your whole own pillar data, merged in order by MakoStack. So MakoStack ext_pillar returns the stack dict, the contents of which Salt takes care to merge in with all of the other pillars and finally return the whole pillar to the minion.

Merging strategies

The way the data from a new yaml_data dict is merged with the existing stack data can be controlled by specifying a merging strategy. Right now this strategy can either be merge-last (the default), merge-first, remove, or overwrite.

Note that scalar values like strings, integers, booleans, etc. are always evaluated using the overwrite strategy (other strategies don't make sense in that case).

The merging strategy can be set by including a dict in the form of:

__: <merging strategy>

as the first item of the dict or list. This allows fine grained control over the merging process.

`merge-last` (default) strategy

If the merge-last strategy is selected (the default), then content of dict or list variables is merged recursively with previous definitions of this variable (similarly to the recurse salt pillar_source_merging_strategy). This allows for extending previously defined data.

`merge-first` strategy

If the merge-first strategy is selected, then the content of dict or list variables are swapped between the yaml_data and stack objects before being merged recursively with the merge-last previous strategy.

`remove` strategy

If the remove strategy is selected, then content of dict or list variables in stack are removed only if the corresponding item is present in the yaml_data dict. This allows for removing items from previously defined data.

`overwrite` strategy

If the overwrite strategy is selected, then the content of dict or list variables in stack is overwritten by the content of yaml_data dict. So this allows one to overwrite variables from previous definitions.

Merging examples

Let's go through small examples that should clarify what's going on when a yaml_data dict is merged in the stack dict.

When you don't specify any strategy, the default merge-last strategy is selected:

`stack`	`yaml_data`	`stack` (after merge)
users: tom: uid: 500 roles: - sysadmin root: uid: 0	users: tom: uid: 1000 roles: - developer mat: uid: 1001	users: tom: uid: 1000 roles: - sysadmin - developer mat: uid: 1001 root: uid: 0

Then you can select a custom merging strategy using the __ key in a dict:

`stack`	`yaml_data`	`stack` (after merge)
users: tom: uid: 500 roles: - sysadmin root: uid: 0	users: __: merge-last tom: uid: 1000 roles: - developer mat: uid: 1001	users: tom: uid: 1000 roles: - sysadmin - developer mat: uid: 1001 root: uid: 0
users: tom: uid: 500 roles: - sysadmin root: uid: 0	users: __: merge-first tom: uid: 1000 roles: - developer mat: uid: 1001	users: tom: uid: 500 roles: - developer - sysadmin mat: uid: 1001 root: uid: 0
users: tom: uid: 500 roles: - sysadmin root: uid: 0	users: __: remove tom: mat:	users: root: uid: 0
users: tom: uid: 500 roles: - sysadmin root: uid: 0	users: __: overwrite tom: uid: 1000 roles: - developer mat: uid: 1001	users: tom: uid: 1000 roles: - developer mat: uid: 1001

You can also select a custom merging strategy using a __ object in a list:

`stack`	`yaml_data`	`stack` (after merge)
users: - tom - root	users: - __: merge-last - mat	users: - tom - root - mat
users: - tom - root	users: - __: merge-first - mat	users: - mat - tom - root
users: - tom - root	users: - __: remove - mat - tom	users: - root
users: - tom - root	users: - __: overwrite - mat	users: - mat