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cfn-make

Minimalistic Makefile for CloudFormation stack deployments.

Motivation

Usage

# mystack.template.yml

Parameters:
  BucketName:
    Type: String

Resources:
  Bucket:
    Type: AWS::S3::Bucket
    Properties:
      BucketName: !Ref BucketName

Outputs:
  Arn: { Value: !GetAtt Bucket.Arn }
# mystack.config.yml

StackName: MyStack

TemplateBody:
  # You can either define the whole template body inline or you can include
  # a reference to an external template file. TemplateBody has to be a string,
  # Fn::Stringify takes care of that.
  Fn::Stringify: !Include mystack.template.yml

Parameters:
  - { ParameterKey: BucketName, ParameterValue: MyBucket }

Capabilities: [CAPABILITY_IAM]

Tags:
  - { Key: Environment, Value: production }
export CONFIG=mystack.config.yml AWS_DEFAULT_REGION=us-east-1
make create
# ---------------------------------------------------
# |                 DescribeStacks                  |
# +------------+------------------------------------+
# |  OutputKey |            OutputValue             |
# +------------+------------------------------------+
# |  Arn       |  arn:aws:s3:::mybucket             |
# +------------+------------------------------------+

# ... make some changes to your template, for example change the bucket name

make stage  # creates a change set and displays changes made to the stack
# ------------------------------------------------------------------------------------------------------------------
# |                                                DescribeChangeSet                                               |
# +--------+------------+--------------+---------------------------+---------------------------+-------------------+
# | Action | LogicalId  | Replacement  | ResourceParameterDynamic  |  ResourceParameterStatic  |       Type        |
# +--------+------------+--------------+---------------------------+---------------------------+-------------------+
# |  Modify|  Bucket    |  True        |  BucketName               |  BucketName               |  AWS::S3::Bucket  |
# +--------+------------+--------------+---------------------------+---------------------------+-------------------+

make update # if you are happy with the changes, execute the change set

Build Stages

Graph

  • init Ensures that all required variables are set and all dependencies are installed.
  • build Compile the configuration file with cfn-include and write the output to a build folder.
  • test Extract the CloudFormation template from the build folder and run validate-template on it.
  • diff Downloads the currently deployed template and generates a diff with the current version of the compiled template.
  • create Create the CloudFormation template and wait for its creation to finish. Prints stack outputs.
  • stage Create a change set of the deployed stack to the current template. Prints diff and change set elements.
  • update Execute the change set. Prints stack outputs.

Build stages have dependencies as defined in the graph. Note that the update stage does not depend on stage. The update stage will fail if the stack has not been staged. If you are certain that you want to run stage and update in one run (without reviewing the change set for potential surprises) you can run make stage update. The name of change set is unique to the template configuration and body. A change to the template or configuration will also change the change set name. A call to update will therefore fail if changes have been made to the template but the change set has not been created yet.

Custom Hooks

All build steps come with pre- and post-hooks. These hooks need to be defined in a separate Makefile that is located in the same directory as the $CONFIG file. If the $CONFIG file is located in the root directory of the project, you should create a new makefile such as hooks.makefile. The environmental variable $ARTIFACT holds the location of the build artifact. If a hook fails so does the whole pipeline.

A simple post-build hook could for example replace the BucketName parameter value with an environmental variable. The corresponding Makefile would look something like this:

# hooks.makefile

post-build:
  sed -i.bak -e "s/MyBucket/$$BUCKET_NAME/" $(ARTIFACT)

Running the build target will indicate that a post-build hook was found and will execute it:

BUCKET_NAME=mynewbucket make build
running post-build hook
sed -i.bak -e "s/MyBucket/$$BUCKET_NAME/" .build/mystack.config.yml.json