Brume: an AWS CloudFormation deployer

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Installation

brume is a Python package and it can be installed with Pip:

$ pip install brume

Usage

In order to use the commands, the current directory must contain a valid configuration file.

Usage: brume [OPTIONS] COMMAND [ARGS]...

Options:
  -v, --version          Show the version and exit.
  -h, --help             Show this message and exit.
  -c, --config FILENAME  Configuration file (defaults to brume.yml).

Commands:
  check       Check CloudFormation templates.
  config      Print the current stack configuration.
  create      Create a new CloudFormation stack.
  delete      Delete the CloudFormation stack.
  deploy      Create or update a CloudFormation stack.
  outputs     Get the full list of outputs of a CloudFormation stack.
  parameters  Get the full list of parameters of a CloudFormation stack.
  status      Get the status of a CloudFormation stack.
  update      Update an existing CloudFormation stack.
  upload      Upload CloudFormation templates and assets to S3
  validate    Validate CloudFormation templates.

These commands always use the current AWS credentials and the stack name from the configuration file (via the --config option).

The brume.yml file

The configuration file requires two configuration blocks stack and templates.

Stack

stack:
  stack_name: my-wordpress-website   # [REQUIRED] the name of the CloudFormation stack
  template_body: Main.cform          # local path to the main CloudFormation template
  template_url: https://my-bucket.s3.amazonaws.com/assets/cloudformation/Main.cform  # complete URL to the main CloudFormation template on S3

The template referenced in stack.template_body or stack.template_url is the entrypoint to your CloudFormation stack (the main or parent stack).

Templates

In case your stack is split between multiple templates, you need to upload the CloudFormation templates to S3 (e.g. using brume upload or the tool of your choice).

If you use brume upload, you need to tell brume where the templates are and where to put them. This is done via the templates section.

templates:
  s3_bucket: my-bucket            # [REQUIRED] name of the bucket in your account in which to store the templates
  s3_path: assets/cloudformation  # path of the S3 folder where the template are uploaded, defaults to `cloudformation`
  local_path: project/cfn         # local path where your CloudFormation templates are, defaults to `.`

Given the above configuration and if you have a Main.cform in project/cfn, the template would be uploaded to https://my-bucket.s3.amazonaws.com/assets/cloudformation/Main.cform.

Assets

If 'assets' configuration is present you can send additionnal resources to target s3 URI (like user data script, application config file, ...).

In your template, you can build assets url like this:

def getAssetUri(asset, bucketName, stackName):
  return '/'.join(['s3://{}'.format(bucketName), stackName, 'assets', asset])

Minimal example

region: eu-west-1

stack:
  stack_name: my-wordpress-website
  template_body: Main.cform

templates:
  s3_bucket: my-bucket

Complete example

brume.yml is in fact a Jinja2 template which means you can declare variables and reuse them in the template. You can also inject environment variables by calling {{ env('MY_VAR') }}.

If the environment variable $MY_VAR does not exist, you can specify a fallback value by passing a second parameter {{ env('MY_VAR', 'FOO') }}.

Also, if the current directory is a git repository (if it contains a .git/ directory), brume exposes a dict named git, that has the three following properties:

• git.commit_sha1 : the SHA1 of the last commit
• git.branch_name : the name of the current branch (warning: if you are in detached mode, the branch name does not exist so it will be HEAD)
• git.commit_msg : the commit message of the last commit

It also exposes two previously available variables: git_commit and git_branch

Their values are taken directly from the current repository.

region: {{ env('AWS_REGION') }}

{% set stack_name = '-'.join([env('PROJECT'), env('ENVIRONMENT'), env('CLASSIFIER')]) %}
stack:
  stack_name: {{ stack_name }}

  template_body: Main.cform
  capabilities: [ CAPABILITY_IAM ]
  on_failure: DELETE

  parameters:
    Project: '{{ env('PROJECT') }}'
    Platform: '{{ env('PLATFORM') }}'
    Classifier: '{{ env('CLASSIFIER') }}'
    GitCommit: '{{ git_commit }}'
    GitBranch: '{{ git_branch }}'

  tags:
    Project: '{{ env('PROJECT') }}'
    Platform: '{{ env('PLATFORM') }}'
    Classifier: '{{ env('CLASSIFIER') }}'

templates:
  s3_bucket: my_bucket
  s3_path: {{ stack_name }}
  local_path: cloudformation

assets:
  s3_bucket: my_bucket
  s3_path: {{ stack_name }}/assets
  local_path: assets

In your Jinja2 template we have predefined function:

• env(var_name) which get value of specified environment variable var_name
• cfn which get output param of specified cloudformation stack.

Example usage of cfn function:

{% set region = env('AWS_REGION') %}
region: {{ region }}

parameters:
  MyParam: {{ cfn(region, 'my_other_stack', 'MyParam') }} # get parameter 'MyParam' of stack 'my_other_stack'
  VPCStackName: {{ cfn(region, 'my_other_stack', 'Vpc', 'VPC_ID') }} # get parameter 'VPC_ID' of nested stack 'Vpc' of stack 'my_other_stack'