rain

Rain

Rain is a development workflow tool for working with AWS CloudFormation.

Rain is currently in preview and shouldn't yet be considered stable enough for production use. Please report any bugs you find through GitHub issues.

Rain is also what happens when you have a lot of CloudFormation

Here's what it looks like:

Installing

You can download the appropriate binary for your system from the releases page.

Alternatively, if you have Go (v1.12 or higher) installed:

GO111MODULE=on go get github.com/aws-cloudformation/rain

License

Rain is licensed under the Apache 2.0 License.

Usage

You will need to make sure you have installed and configured the AWS CLI as rain uses the same credentials and configuration.

Rain is composed of a number of sub-commands. Invoke a command like this:

rain [command] [arguments...]

The following commands are available:

cat         Get the CloudFormation template from a running stack
check       Show your current configuration
deploy      Deploy a CloudFormation stack from a local template
diff        Compare CloudFormation templates
logs        Show the event log for the named stack
ls          List running CloudFormation stacks
rm          Delete a running CloudFormation stack

You can get additional information about any command by running:

rain help [command]

Design Principles

Rain is designed with the following principles in mind:

Do the most obvious and useful thing by default

The default behaviour for every feature of rain should:

• do what you would expect from the name
• output only the most pertinent information
• have a high signal to noise ratio

Examples:

• ls lists stacks in the current region, showing only the stack name and status

Have consistent options available for non-default behaviour

While the default behaviour should stick to the obvious, every command should offer options for other use cases.

Examples:

• -a | --all shows information that would otherwise be filtered:

  • ls -a lists stacks in all regions
  • logs -a shows uninteresting logs

• -l | --long shows more detailed information:

  • logs -l shows all available log details

Be human-friendly

Output should:

• be easy to read, making good use of white-space while taking up the minimum of space needed to convey the important information
• use colour to highlight things the user needs to be aware of
• use colour to differentiate different kinds of information
• show progress so that the user knows we haven't crashed

Examples:

• All commands colourise the stack/resource status
• logs colours the message field so that it stands out
• deploy shows a "spinner" while working

Be machine-friendly

Output should:

• be consumable by other processes; use YAML where possible
• strip special formatting when it is part of a pipe

Examples:

• All commands (except ls for now) output in YAML-compatible output
• All commands strip formatting if stdout is not connected to a terminal

Other CloudFormation tools

In alphabetical order:

• cfn-flip

  cfn-flip converts AWS CloudFormation templates between JSON and YAML formats, making use of the YAML format's short function syntax where possible.

• cfn-format

  cfn-format reads in an existing AWS CloudFormation template and outputs a cleanly-formatted, easy-to-read copy of the same template adhering to standards as used in AWS documentation. cfn-format can output either YAML or JSON as desired.

• cfn-lint

  Validate CloudFormation yaml/json templates against the CloudFormation spec and additional checks. Includes checking valid values for resource properties and best practices.

• cfn-skeleton

  cfn-skeleton that consumes the published CloudFormation specification and generates skeleton CloudFormation templates with mandatory and optional parameters of chosen resource types pre-filled with placeholder values.

• taskcat

  taskcat is a tool that tests AWS CloudFormation templates. It deploys your AWS CloudFormation template in multiple AWS Regions and generates a report with a pass/fail grade for each region. You can specify the regions and number of Availability Zones you want to include in the test, and pass in parameter values from your AWS CloudFormation template. taskcat is implemented as a Python class that you import, instantiate, and run.

Are we missing an excellent tool? Let us know via a GitHub issue.