Streamlined Deployments: Triggering CodePipeline from CodeCommit Merge Requests

Continuous integration and continuous delivery (CI/CD) pipelines automate deployments. However, triggering builds and deployments only when necessary is crucial for efficiency. This article explores setting up AWS CodePipeline to trigger deployments upon code merges to the main branch in an AWS CodeCommit repository. We'll leverage CodeCommit branch protection rules and configure CodePipeline to react to merge requests, automating deployments for approved code changes.

1. Enforcing Guardrails: Branch Protection Rules in CodeCommit

• Navigate to the AWS CodeCommit console and select the repository containing your code.
• In the navigation pane, click "Settings."
• Locate the "Branch permissions" section and click "Manage branch permissions."

Creating Branch Protection Rules:

• Click "Create branch protection rule."
• Provide a descriptive name for the rule (e.g., "Main Branch Protections").
• Under "Patterns," choose "Branch name" and specify the main branch name (e.g., "main").

Enforcing Merge Requirements:

Here's how to configure rules to enforce code review before merging:

• Enable "Require at least one approval before merging."
• Choose "Approval pool" and select the users or groups who can approve pull requests (e.g., a development team).

Optional: Restricting Direct Pushes:

For additional control, you can prevent direct pushes to the main branch:

• Disable "Allow direct pushes to this branch."

These rules ensure that only approved merge requests (following a review process) can be merged into the main branch, triggering the automated deployment pipeline.

2. Connecting the Pipeline: Triggering on Merge Requests

• Navigate to the AWS CodePipeline console and select the pipeline you want to modify.

Trigger Configuration:

• Within the pipeline details, locate the "Source" stage.
• Click the edit icon next to the source provider configuration.

Specifying Merge Request Trigger:

Here's how to configure the pipeline to trigger on merge requests:

• Under "Trigger," choose "Merge request."
• Select the CodeCommit repository containing your code.
• Optionally, filter branches by selecting "Branch name" and specifying the main branch name (e.g., "main").

Understanding Merge Request Trigger:

This configuration instructs the pipeline to listen for merge requests targeting the main branch in the specified CodeCommit repository. Upon a successful merge (meeting the branch protection rules), the pipeline execution will automatically trigger.

3. Deployment Automation: Continuous Delivery from Merges

Ensure your pipeline stages are configured to handle the entire deployment process, including building, testing (if applicable), and deployment to your chosen environment (e.g., using CodeDeploy or AWS Elastic Beanstalk).

Automatic Deployments:

With the pipeline trigger configured, the following workflow emerges:

1. A developer creates a pull request in the CodeCommit repository.
2. The pull request undergoes code review and potentially additional checks (depending on branch protection rules).
3. Once approved, the pull request is merged into the main branch.
4. CodePipeline detects the merge event due to the configured trigger.
5. The pipeline execution automatically starts, initiating the build, testing, and deployment process for the merged code changes.

By leveraging CodeCommit branch protection rules and CodePipeline triggers, you establish a controlled and automated deployment workflow. Code changes are reviewed and approved before merging, and the pipeline efficiently handles deployments for validated code.

Additional Considerations:

• You can configure pipeline notifications to alert developers upon successful deployments triggered by merge requests.
• For advanced scenarios, consider integrating CodeBuild with CodeCommit for pre-build checks before code reaches the main branch, further enhancing code quality.

This approach streamlines deployments, reduces manual intervention, and enforces code review practices, leading to a more robust and efficient CI/CD pipeline.