Packaging¶

cfnrain adds features to the CloudFormation template language. CloudFormation does not know these features, so cfnrain turns them into a plain template before it sends the template to AWS. This step is packaging.

Packaging processes:

• Template directives, such as !Rain::Embed and !Rain::S3
• Constants
• Modules, including ForEach, conditions and the extra intrinsic functions
• Implicit uploads: local paths in resource properties that take an S3 location

Files that packaging uploads go to the artifact bucket.

Which commands package¶

These commands package the template before they use it: pkg, deploy, forecast, stackset deploy and cc deploy.

cfnrain pkg packages a template and prints the result. Use it to see what CloudFormation gets:

cfnrain pkg app.yaml -o app.packaged.yaml

Run linters such as cfn-lint on the packaged template, because they do not know the cfnrain features.

Paths¶

A path in a template is relative to the directory of the template file that contains it. It is not relative to the directory where you run cfnrain. In an included file or a module, paths are relative to that file.

Templates can run code¶

Two features run programs from your computer:

• Run in !Rain::S3 runs a script when cfnrain packages the template.
• RunBefore and RunAfter in S3 bucket metadata run commands when cfnrain deploys the template.

Run works without --experimental. Only package and deploy templates that you trust.