Orchestrating Seamless Rollouts: Blue/Green Deployments with CodePipeline and CodeDeploy

Blue/green deployments are a popular strategy for minimizing downtime during application updates. This article explores implementing blue/green deployments using AWS CodePipeline and AWS CodeDeploy. We'll delve into setting up identical environments, leveraging CodeDeploy for traffic routing, and configuring CodePipeline to automate the blue/green deployment process.

1. Building the Foundation: Identical Blue and Green Environments

• Provision two identical environments within your AWS infrastructure (e.g., using AWS CloudFormation or Infrastructure as Code tools like Terraform).
• These environments will be referred to as "blue" (currently active) and "green" (the new deployment target).
• Ensure both environments have identical configurations, including:
  • EC2 instances or serverless functions running your application.
  • Load balancers distributing traffic to the instances or functions.
  • Database connections and other configuration settings.

Load Balancer Configuration:

Crucially, configure your load balancer to initially route all traffic to the instances or functions within the blue environment. This ensures the blue environment serves production traffic.

2. Leveraging CodeDeploy: Traffic Routing and Deployments

• For each environment (blue and green), create a dedicated CodeDeploy application and deployment group.
• The CodeDeploy application serves as a logical container for your deployments.
• The deployment group defines the specific instances or functions where CodeDeploy will deploy your application code.

Traffic Routing with CodeDeploy:

CodeDeploy offers functionalities for traffic routing during deployments. We'll utilize this feature to seamlessly switch traffic between the blue and green environments.

3. Building the Pipeline: Automating Blue/Green Deployments

• Navigate to the AWS CodePipeline console and click "Create pipeline" to define a new pipeline.
• Provide a descriptive name for your pipeline (e.g., "blue-green-deployment").
• Choose "New service role" to allow CodePipeline to create a role with necessary permissions.

Connecting to CodeCommit:

• In the "Source provider" section, select "AWS CodeCommit."
• Choose the CodeCommit repository containing your application code.
• Click "Next" to proceed with configuring the pipeline stages.

Creating Stages:

We'll establish three stages within the pipeline:

1. Build: This stage utilizes a build provider like AWS CodeBuild to build and potentially test your application code.
2. Deploy to Green: This stage deploys the newly built code to the green environment using CodeDeploy.
3. Swap Environments: This stage utilizes CodePipeline to automate the traffic routing between blue and green environments after a successful deployment.

Configuring the "Deploy to Green" Stage:

• Within the "Deploy to Green" stage configuration, choose "AWS CodeDeploy" as the deployment provider.
• Select the CodeDeploy application and deployment group associated with the green environment.

4. The Swap Stage: Orchestrating Traffic Routing

• Navigate to the "Swap Environments" stage configuration within your pipeline.
• Click the "Actions" tab and choose "AWS CodeBuild" as the action type. This might seem counterintuitive, but we'll use CodeBuild to execute a script for traffic routing.

CodeBuild Script for Traffic Routing:

Here's a basic example script for a CodeBuild project within the "Swap Environments" stage (replace placeholders with your actual details):

version: 0.2

phases:
  build:
    commands:
      - aws elbv2 modify-target-groups --target-group-arn <blue-target-group-arn> --deregister-target-ids <green-instance-id>
      - aws elbv2 modify-target-groups --target-group-arn <green-target-group-arn> --register-target-ids <green-instance-id>

post_build:
  commands:
    - echo "Traffic successfully routed to the green environment."

Explanation:

• This script leverages the AWS CLI to interact with AWS Elastic Load Balancing v2 (ELBv2).
• It deregisters the green instance from the blue target group, effectively removing it from receiving traffic.
• Conversely, it registers the green instance with the green target group, directing traffic to the newly deployed code.

Permissions and Security:

Ensure the IAM role associated with the CodeBuild project used in the "Swap Environments" stage has the necessary permissions to perform the ELBv2 actions within the script.