CDK PR 2 Pipeline

There are times when feature-based development with git is preferred.

According to Atlassian: "The core idea behind the Feature Branch Workflow is that all feature development should take place in a dedicated branch instead of the main branch. This encapsulation makes it easy for multiple developers to work on a particular feature without disturbing the main codebase. It also means the main branch will never contain broken code, which is a huge advantage for continuous integration environments."

Currently, AWS CodePipeline does not natively support constructing a stack when a PR is created in GitHub. This construct enables this functionality.

Setup

• add your github token to AWS Secrets Manager with the key named github-token
  • this can be changed in example/pipeline-stack.ts where the sourceAction is defined
• alter the github info in example/example-app.ts for your project
• from the root directory run npm install to fetch the dependencies
• ensure you have bootstrapped cdk for your account
• npm run deploy to deploy into your account

Try It

• in your AWS web console, browse to CloudFormation
  • you should see a deployment for the main branch
• browse to CodePieline and you should see a pipeline for main
• browse to CodeBuild and you should see a Project for PR2Pipeline
• in github, make a new branch and generate a pull request
• this should have triggered PR2Pipeline project, which in turn will deploy a new stack for the branch in CloudFormation
  • you will have to manually approve deployment
• in github, close the pull request
  • you should now see the stack being deleted

How it works

• A custom Codebuild project is made that listens for specific webhook events from github, PULL_REQUEST_CREATED, PULL_REQUEST_REOPENED, and PULL_REQUEST_MERGED.
  • If the event is PULL_REQUEST_CREATED and PULL_REQUEST_REOPENED, then it builds a new stack for that branch
  • If it is PULL_REQUEST_MERGED, then it deletes the stack for that branch
• Everything else is a standard codepipeline that is listening to the main branch

Example

An example of how to integrate into cdk.pipelines is provided in example/pipeline-stack.ts. In particular, note how it is checking the branch name to determine if it should do the normal pipeline actions for test/prod/etc, or if it should deploy into dev account the stack based on the feature branch identified in the webhook. A generic representative application is provided in the example.

Notes about the example

• the github token has been stored in Secrets Manager
• the pr-to-pipeline construct is only deployed when the branch is main, not for any feature branch, since it is what stands up the feature branch stack
• any s3 buckets created by this example will have to be manually deleted