ssm-ps-template 1.1.0

CLI for rendering configuration templates with SSM Parameter Store as a data source

SSM Parameter Store Template

Command line application to render templates with data from SSM Parameter Store

Installation

The ssm-ps-template application is available via the Python Package Index and can be installed with pip:

pip install ssm-ps-template

Templating

The application uses Jinja2 for the templating engine.

Configuration

The configuration file provides the ability to specify multiple templates, override AWS configuration, and change logging levels:

Top-Level Configuration Directives

Directive	Description
templates	An array of template directives as detailed in the next table.
endpoint_url	Specify an endpoint URL to use to override the default URL used to contact SSM Parameter Store
profile	Specify the AWS profile to use. If unspecified will default to the AWS_DEFAULT_PROFILE environment variable or is unspecified
region	Specify the AWS region to use. If unspecified it will default to the AWS_DEFAULT_REGION environment variable or is unspecified
verbose	Turn debug logging on. Possible values are true and false

Template Configuration Directives

The templates directive in the configuration is an array of objects, defined by a source and destination.

Directive	Description
source	The source file of the template
destination	The destination path to write the rendered template to
prefix	The prefix to prepend variables with if they do not start with a forward-slash (/)

Extended Templating Functionality

In addition to the base functionality exposed by Jinja2, the following Python functions have been added:

Function	Definition
urlparse	The urllib.parse.urlparse function from the Python standard library.
parse_qs	The urllib.parse.parse_qs function from the Python standard library.
unquote	The urllib.parse.unquote function from the Python standard library.

The following filters are added:

Filter	Description
toyaml	Converts a dictionary value to YAML

The following variables are exposed:

Variable	Definition
environ	The os.environ dictionary for accessing environment variables

Configuration File Format

The application supports JSON, TOML, or YAML for configuration. The following example is in YAML:

Example Configuration File

templates:
  - source: /etc/ssm-templates/nginx-example
    destination: /etc/nginx/sites-available/example
    prefix: /namespaced/application/nginx/
  - source: /etc/ssm-templates/postgres-example
    destination: /etc/postgresql/14/main/postgresql.conf
    prefix: /namespaced/application/postgres/
profile: default
region: us-east-1
verbose: false

Path Based Dictionaries

In more complex templates it's possible to need a dictionary of values from SSM instead of straight key/value usage.

This is achieved by setting a variable to a key with a trailing slash (/).

The following pattern will retrieve all keys under a path and return them as a nested dictionary with a / delimiter, and then iterate over the key/value pairs:

{% set values = settings/ %}
{% for key, value in settings.items() %}
  {{ key }}: {{ value }}
{% endfor %}

Or to convert them to YAML:

settings: {% set values = settings/ %}
{{ values | toyaml | indent(2, first=True) }}

Command Line Usage

usage: ssm-ps-template [-h] [--aws-profile AWS_PROFILE] [--aws-region AWS_REGION] [--prefix PREFIX] [--verbose] config

Templating for SSM Parameter Store

positional arguments:
  config

optional arguments:
  -h, --help            show this help message and exit
  --aws-profile AWS_PROFILE
                        AWS Profile
  --aws-region AWS_REGION
                        AWS Region
  --endpoint-url ENDPOINT_URL
                        Specify an endpoint URL to use when contacting SSM Parameter Store.
  --prefix PREFIX       Default SSM Key Prefix
  --replace-underscores
                        Replace underscores in variable names to dashes when looking for values in SSM
  --verbose

Note that the default SSM prefix can also be set with the PARAMS_PREFIX environment variable and the endpoint URL setting cn be set with the ENDPOINT_URL environment variable.