carlnordenfelt / aws-cloudformation-simple-cli Goto Github PK

I would love to have the ability to load placeholders from a file as opposed to having to pass them on the command line.

I find I like to use the same .config file for multiple environments (e.g. dev, prod) and just make minor tweaks to some values (e.g. prepending stack names and tag names with the environment name, or changing the first two octets of VPC and subnet CIDRs which are passed as parameters, etc.). When you have multiple environments with multiple placeholders, this gets cumbersome.

An alternative is writing an all new .config for each environment, but in complicated .config files this makes things much less DRY. I often have very flexible CFN templates which use a lot of parameters. Those parameters don't change much between environments of the same project, (but may change a lot between projects) so it'd be nice to use the same .config for each environment in a project, with an additional file (.placeholders?) to hold small differences between environments.

A couple examples of how this could be implemented: adding a placeholder-file option, or extending the existing placeholder option to be similar to how the AWS CLI --parameters flag works, where it can take a shorthand syntax or file://... as a value.

Deploying two different environments for the same project may look like:

dev.placeholders:

{
  "{Namespace}": "Dev",
  "{CidrPrefix}": "10.0"
}

prod.placeholders:

{
  "{Namespace}": "Prod",
  "{CidrPrefix}": "10.1"
}

Shell commands to create stacks DevVpc and ProdVpc:

$ aws-cfn create --config-file project.config --environment vpc --placeholder-file dev.placeholders
$ aws-cfn create --config-file project.config --environment vpc --placeholder-file prod.placeholders

If you think this is an idea that you'd like to incorporate into the main project, I could take a first crack at implementing it and make a PR.