Abstract

• Continue the previous post Hands-on Amazon ECS for Blue-Green Deployments With CDK Typescript which uses EC2 to host the ECS container service and manually operate blue-green deployments. In this blog post, I use AWS Fargate as a container of ECS service and codedeploy to operate blue-green deployment automatically.

Table Of Contents

• Solution overview
• Source code structure
• Process flow
• Cleanup
• Conclusion

🚀 Solution overview

• The whole AWS resources are created using CDK pipeline except the pipeline itself.
• The ECS cluster is placed in private subnet as well as the fargate service. We create ECS service with task definition that has desired count of 3 and use FARGATE as requiresCompatibilities
• The ECS service is registered to ECS deployment controller with the type CODE_DEPLOY for handling blue-green deployment. It sticks the application load balancer to the replacement target group when deploying successfully.
• A container image is built with codepipeline and codebuild which store images to ECR.
• Here is the stacks relationship

🚀 Source code structure

• We have two Git repositories (codecommit) one for application project app-project directory and others for CDK infrastructure cdk-infra directory

 ➜ ecs-blue-green-deployments tree -L 1
 .
 ├── README.md
 ├── app-project
 ├── cdk-infra
 └── images
 3 directories, 1 file

• We create the codecommit repositories through CDK

  • Go to cdk-infra and run cdk ls

  cdk ls
  simflexcloud-ecs-blue-green-deployments-pipeline
  simflexcloud-ecs-blue-green-deployments-pipeline/master-sin/EcsBlueGreenDeploymentsStack
  

  • Deploy simflexcloud-ecs-blue-green-deployments-pipeline it will create the repository of cdk-infra. Note: replace CDK_DEFAULT_ACCOUNT and CDK_DEFAULT_REGION in cdk-infra/src/shared/constants.ts with expected ones.

  cdk deploy simflexcloud-ecs-blue-green-deployments-pipeline
  

  • Add the remote Git repository to cdk-infra (Note: Replace the priv-acc with yours)

  git remote add origin ssh://priv-acc/v1/repos/ecs-blue-green-deployments-infra
  

  • Create branch master and push source code to the repo, it will trigger CDK pipeline to create all stacks which also include the repository and pipeline for app-proj
  • After the pipeline is completed successfully, go to app-proj directory and add Git remote repository, then create the branches testgreen and testblue and push them to codecommit

  git remote add origin ssh://priv-acc/v1/repos/simflexcloud-ecs-blue-green-deployments
  

🚀 Process flow

1. Build project

• Use AWS CodeBuild to create Docker images and store them in Amazon ECR. This process is powered by codepipeline to handle CICD.

2. Create ECS cluster

• Create an Amazon ECS cluster using fargate.

  

3. Application load balancer

• We have two rules:

  • Port 80: the main rule

  

  • Port 8080: testing rule

  

• The ALB is currently stuck to the target group of green

  

4. CodeDeploy application and deployment group

• A CodeDeploy deployment group that orchestrates ECS blue-green deployments.

  

🚀 Test the blue-green deployments

• Test the blue service by loading ALB DNS

• Now we change the color to red in app-proj/index.html and push the commit to CodeCommit. It triggers the pipeline to build and then deploy a new change

• The deploy stage creates codedeploy deployment ID to perform the deployment process and handle the Traffic shifting progress strategy with rule LINEAR_10PERCENT_EVERY_1MINUTES (CodeDeploy predefined deployment configuration that shifts 10 percent of traffic every minute until all traffic is shifted)

• ECS run new tasks with new image version on the ECS service

• After the new tasks are in healthy state, the deployment starts rerouting production traffic to replacement task set gradually following the rule LINEAR_10PERCENT_EVERY_1MINUTES

• Use port 8080 for testing and compare with current version

• Complete the replacement and start terminating the original task set

• ECS remove the tasks with old revision

• The final result

🚀 Cleanup

• To cleanup all resources in this project, we first need to delete the ECR image as they were not created by CDK and prevent CDK to destroy the ECR repository.
• Go to cloudformation and delete stacks.

🚀 Conclusion

• Now that you know how to launch tasks into your Amazon ECS cluster using CDK pipeline with the required type EC2 or Fargate.
• The approach of a blue-green deployment involves utilizing two identical production environments as a means of reducing downtime. Various cutover strategies may be employed, but typically only one of the environments should be actively serving production traffic.

References:

• BLUE/GREEN DEPLOYMENTS ON ECS FARGATE