cf-macro-jsonet

Evaluate arbitrary jsonnet code in your CloudFormation templates.

Basic Usage

Place jsonnet code as a text block anywhere in your template, the text block will be replaced with its evaluation.

The following bindings are added to the snippet scope:

• templateParams: the top-level template parameters
• template: the entire template
• accountId: AWS account ID
• region: AWS Region

AWSTemplateFormatVersion: "2010-09-09"
Transform: [Jsonnet]
Resources:
  S3Bucket:
    Type: "AWS::S3::Bucket"
    Properties:
      Tags: |
        #!jsonnet
        local tags = {
          Project: 'take-over-the-world',
          Stage: 'testing'
        };
        [{ Key: k, Value: tags[k] } for k in std.objectFields(tags)]

Using a library

The template parameter JsonnetLibraryUri can be used to provide an URI to a zip-file that will act as a search path for jsonnet imports.

Example:

• Upload to S3 a Zip file containing a file utils.jsonnet with the following content:

  {
    toEntries(obj): [{ Key: k, Value: obj[k] } for k in std.objectFields(obj)]
  }
  

• Now you can use toEntries like the following

  AWSTemplateFormatVersion: "2010-09-09"
  Transform: [Jsonnet]
  JsonnetLibraryUri: s3://path/to/zip/file/above
  Resources:
    S3Bucket:
      Type: "AWS::S3::Bucket"
      Properties:
        Tags: |
          #!jsonnet
          local utils = import "utils.jsonnet";
          utils.toEntries({
            Project: 'take-over-the-world',
            Stage: 'testing'
          })

Development

• Compile the Python jsonnet bindings into a replica of the lambda environemnt

  $ docker run -it --rm -v $PWD/src:/var/task lambci/lambda:build-python3.6 pip install -t . jsonnet
  

• Use the SAM cli to tests the code locally

  $ sam local invoke --event ./examples/event.json
  

• Deploy to AWS Lambda

  $ sam package --template-file template.yml --s3-bucket ${BUCKET_NAME} --output-template /tmp/template.yml
  $ sam deploy --template-file /tmp/template.yml --stack-name cf-macro-jsonnet --capabilities CAPABILITY_IAM
  

TODO

• more meaningful examples
• proper testing

License

MIT License

Author

Andrea Bedini, KZN Group