[![Unit tests](https://github.com/aws-cloudformation/rain/actions/workflows/test.yml/badge.svg)](https://github.com/aws-cloudformation/rain/actions/workflows/test.yml) [![Mentioned in Awesome CloudFormation](https://awesome.re/mentioned-badge-flat.svg)](https://github.com/aws-cloudformation/awesome-cloudformation) # Rain * Documentation: > Rain is what happens when you have a lot of CloudFormation Rain is also a command line tool for working with [AWS CloudFormation](https://aws.amazon.com/cloudformation/) templates and stacks. [![Make it Rain](./docs/rain.svg)](https://asciinema.org/a/vtbAXkriC0zg0T2UzP0t63G4S?autoplay=1) ## Discord Join us on Discord to discuss rain and all things CloudFormation! Connect and interact with CloudFormation developers and experts, find channels to discuss rain, the CloudFormation registry, StackSets, cfn-lint, Guard and more: [![Join our Discord](https://discordapp.com/api/guilds/981586120448020580/widget.png?style=banner3)](https://discord.gg/9zpd7TTRwq) ## Key features * **Interactive deployments**: With `rain deploy`, rain packages your CloudFormation templates using [`aws cloudformation package`](https://awscli.amazonaws.com/v2/documentation/api/latest/reference/cloudformation/package.html), prompts you for any parameters that have not yet been defined, shows you a summary of the changes that will be made, and then displays real-time updates as your stack is being deployed. Once finished, you get a summary of the outcome along with any error messages collected along the way - including errors messages for stacks that have been rolled back and no longer exist. * **Consistent formatting of CloudFormation templates**: Using `rain fmt`, you can format your CloudFormation templates to a consistent standard or reformat a template from JSON to YAML (or YAML to JSON if you prefer). Rain preserves your comments when using YAML and switches use of [intrinsic functions](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/intrinsic-function-reference.html) to use the short syntax where possible. * **Combined logs for nested stacks with sensible filtering**: When you run `rain log`, you will see a combined stream of logs from the stack you specified along with any nested stack associated with it. Rain also filters out uninteresting log messages by default so you just see the errors that require attention. * **Build new CloudFormation templates**: `rain build` generates new CloudFormation templates containing skeleton resources that you specify. This saves you having to look up which properties are available and which are required vs. optional. * **Manipulate CloudFormation stack sets**: `rain stackset deploy` creates a new stackset, updates an existing one or adds a stack instance(s) to an existing stack set. You can list stack sets using `rain stackset ls`, review stack set details with `rain stackset ls ` and delete stack set and\or its instances with `rain stackset rm ` * **Predict deployment failures** (EXPERIMENTAL): `rain forecast` analyzes a template and the target deployment account to predict things that might go wrong when you attempt to create, update, or delete a stack. This command speeds up development by giving you advanced notice for issues like missing permissions, resources that already exist, and a variety of other common resource-specific deployment blockers. * **Modules** (EXPERIMENTAL): `rain pkg` supports client-side module development with the `!Rain::Module` directive. Rain modules are partial templates that are inserted into the parent template, with some extra functionality added to enable extending existing resource types. _Note that in order to use experimental commands, you have to add `--experimental` or `-x` as an argument._ ## Getting started If you have [homebrew](https://brew.sh/) installed, `brew install rain` Or you can download the appropriate binary for your system from [the releases page](https://github.com/aws-cloudformation/rain/releases). Or if you're a [Gopher](https://blog.golang.org/gopher), you can `GO111MODULE=on go install github.com/aws-cloudformation/rain/cmd/rain` ``` Usage: rain [command] Stack commands: cat Get the CloudFormation template from a running stack deploy Deploy a CloudFormation stack from a local template logs Show the event log for the named stack ls List running CloudFormation stacks rm Delete a running CloudFormation stack stackset This command manipulates stack sets. watch Display an updating view of a CloudFormation stack Template commands: bootstrap Creates the artifacts bucket build Create CloudFormation templates diff Compare CloudFormation templates fmt Format CloudFormation templates forecast Predict deployment failures merge Merge two or more CloudFormation templates pkg Package local artifacts into a template tree Find dependencies of Resources and Outputs in a local template Other Commands: console Login to the AWS console help Help about any command info Show your current configuration ``` You can find shell completion scripts in [docs/bash_completion.sh](./docs/bash_completion.sh) and [docs/zsh_completion.sh](./docs/zsh_completion.sh). ## Contributing Rain is written in [Go](https://golang.org/) and uses the [AWS SDK for Go v2](https://github.com/aws/aws-sdk-go-v2). To contribute a change to Rain, [fork this repository](https://github.com/aws-cloudformation/rain/fork), make your changes, and submit a Pull Request. ### Go Generate The `README.md`, documentation in `docs/`, the auto completion scripts and a copy of the cloudformation specification in `cft/spec/cfn.go` are generated through `go generate`. ## License Rain is licensed under the Apache 2.0 License. ## Example Usage ### Packaging The `rain pkg` command can be used as a replacement for the `aws cloudformation package` CLI command. When packaging a template, `rain` looks for specific directives to appear in resources. #### Embed The `!Rain::Embed` directive simply inserts the contents of a file into the template as a string. The template: ```yaml Resources: Test: Type: AWS::CloudFormation:WaitHandle Metadata: Comment: !Rain::Embed embed.txt ``` The contents of `embed.txt`, which is in the same directory as the template: ```txt This is a test ``` The resulting packaged template: ```yaml Resources: Test: Type: AWS::CloudFormation:WaitHandle Metadata: Comment: This is a test ``` #### Include The `!Rain::Include` directive parses a YAML or JSON file and inserts the object into the template. The template: ```yaml Resources: Test: !Rain::Include include-file.yaml ``` The file to be included: ```yaml Type: AWS::S3::Bucket Properties: BucketName: test ``` The resulting packaged template: ```yaml Resources: Test: Type: AWS::S3::Bucket Properties: BucketName: test ``` #### Env The `!Rain::Env` directive reads environment variables and inserts them into the template as strings. The template: ```yaml Resources: Test: Type: AWS::S3::Bucket Properties: BucketName: !Rain::Env BUCKET_NAME ``` The resulting packaged template, if you have exported an environment variable named `BUCKET_NAME` with value `abc`: ```yaml Resources: Test: Type: AWS::S3::Bucket Properties: BucketName: abc ``` #### S3Http The `!Rain::S3Http` directive uploads a file or directory to S3 and inserts the HTTPS URL into the template as a string. The template: ```yaml Resources: Test: Type: A::B::C Properties: TheS3URL: !Rain::S3Http s3http.txt ``` If you have a file called `s3http.txt` in the same directory as the template, rain will use your current default profile to upload the file to the artifact bucket that rain creates as a part of bootstrapping. If the path provided is a directory and not a file, the directory will be zipped first. ```yaml Resources: Test: Type: A::B::C Properties: TheS3URL: https://rain-artifacts-012345678912-us-east-1.s3.us-east-1.amazonaws.com/a84b588aa54068ed4b027b6e06e5e0bb283f83cf0d5a6720002d36af2225dfc3 ``` #### S3 The `!Rain::S3` directive is basically the same as `S3Http`, but it inserts the S3 URI instead of an HTTPS URL. The template: ```yaml Resources: Test: Type: A::B::C Properties: TheS3URI: !Rain::S3 s3.txt ``` If you have a file called `s3.txt` in the same directory as the template, rain will use your current default profile to upload the file to the artifact bucket that rain creates as a part of bootstrapping. If the path provided is a directory and not a file, the directory will be zipped first. ```yaml Resources: Test: Type: A::B::C Properties: TheS3URI: s3://rain-artifacts-755952356119-us-east-1/a84b588aa54068ed4b027b6e06e5e0bb283f83cf0d5a6720002d36af2225dfc3 ``` If instead of providing a path to a file, you supply an object with properties, you can exercise more control over how the object is uploaded to S3. The following example is a common pattern for uploading Lambda function code. ```yaml Resources: MyFunction: Type: AWS::Lambda::Function Properties: Code: !Rain::S3 Path: lambda-src Zip: true BucketProperty: S3Bucket KeyProperty: S3Key ``` The packaged template: ```yaml Resources: MyFunction: Type: AWS::Lambda::Function Properties: Code: S3Bucket: rain-artifacts-012345678912-us-east-1 S3Key: 1b4844dacc843f09941c11c94f80981d3be8ae7578952c71e875ef7add37b1a7 ``` #### Module The `!Rain::Module` directive is an experimental feature that allows you to create local modules of reuseable code that can be inserted into templates. A rain module is similar in some ways to a CDK construct, in that a module can extend an existing resource, allowing the user of the module to override properties. For example, your module could extend an S3 bucket to provide a default implementation that passes static security scans. Users of the module would inherit these best practices by default, but they would still have the ability to configure any of the original properties on `AWS::S3::Bucket`, in addition to the properties defined as module parameters. In order to use this feature, you have to acknowledge that it's experimental by adding a flag on the command line: `rain pkg -x my-template.yaml` Keep in mind that with new versions of rain, this functionality could change, so use caution if you decide to use this feature for production applications. The `rain pkg` command does not actually deploy any resources if the template does not upload any objects to S3, so you always have a chance to review the packaged template. It's recommended to run linters and scanners on the packaged template, rather than a pre-processed template that makes use of these advanced directives. A sample module: ```yaml Description: | This module extends AWS::S3::Bucket Parameters: LogBucketName: Type: String Resources: ModuleExtension: Metadata: Extends: AWS::S3::Bucket Properties: LoggingConfiguration: DestinationBucketName: !Ref LogBucket BucketEncryption: ServerSideEncryptionConfiguration: - ServerSideEncryptionByDefault: SSEAlgorithm: AES256 PublicAccessBlockConfiguration: BlockPublicAcls: true BlockPublicPolicy: true IgnorePublicAcls: true RestrictPublicBuckets: true Tags: - Key: test-tag Value: test-value1 LogBucket: Type: AWS::S3::Bucket DeletionPolicy: Retain Properties: BucketName: !Ref LogBucketName BucketEncryption: ServerSideEncryptionConfiguration: - ServerSideEncryptionByDefault: SSEAlgorithm: AES256 VersioningConfiguration: Status: Enabled PublicAccessBlockConfiguration: BlockPublicAcls: true BlockPublicPolicy: true IgnorePublicAcls: true RestrictPublicBuckets: true ``` A module must include a resource called `ModuleExtension`, and it must indicate which resource it is extending with a Metadata entry called `Extends`. Note that we defined a single parameter to the module called `LogBucketName`. In the module, we create an additional bucket to hold logs, and we apply the name to that bucket. In the template that uses the module, we specify that name as a property. This shows how we have extended the basic behavior of a bucket to add something new. A template that uses the module: ```yaml Resources: ModuleExample: Type: !Rain::Module "./bucket-module.yaml" UpdateReplacePolicy: Delete Properties: LogBucketName: test-module-log-bucket VersioningConfiguration: Status: Enabled Tags: - Key: test-tag Value: test-value2 ``` Note that in addition to supplying the expected `LogBucketName` property, we have also decided to override a few of the properties on the underlying `AWS::S3::Bucket` resource, which shows the flexibility of the inheritance model. The resulting template after running `rain pkg`: ```yaml Resources: ModuleExample: Type: AWS::S3::Bucket Properties: LoggingConfiguration: DestinationBucketName: !Ref ModuleExampleLogBucket BucketEncryption: ServerSideEncryptionConfiguration: - ServerSideEncryptionByDefault: SSEAlgorithm: AES256 PublicAccessBlockConfiguration: BlockPublicAcls: true BlockPublicPolicy: true IgnorePublicAcls: true RestrictPublicBuckets: true Tags: - Key: test-tag Value: test-value2 VersioningConfiguration: Status: Enabled ModuleExampleLogBucket: DeletionPolicy: Retain Type: AWS::S3::Bucket Properties: BucketName: test-module-log-bucket BucketEncryption: ServerSideEncryptionConfiguration: - ServerSideEncryptionByDefault: SSEAlgorithm: AES256 VersioningConfiguration: Status: Enabled PublicAccessBlockConfiguration: BlockPublicAcls: true BlockPublicPolicy: true IgnorePublicAcls: true RestrictPublicBuckets: true ``` ## Other CloudFormation tools * [cfn-lint](https://github.com/aws-cloudformation/cfn-python-lint) Validate CloudFormation yaml/json templates against the CloudFormation spec and additional checks. Includes checking valid values for resource properties and best practices. * [cfn-guard](https://docs.aws.amazon.com/cfn-guard/latest/ug/what-is-guard.html) Guard is a policy evaluation tool that allows you to build your own rules with a custom DSL. You can also pull rules from the [guard registry](https://github.com/aws-cloudformation/aws-guard-rules-registry) to scan your templates for resources that don't comply with common best practices. * [taskcat](https://github.com/aws-quickstart/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.