Amazon ECS Farget with Blue-Green Deployments by CDK Typescript - Part 2

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

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🚀 Solution overview

• The whole AWS resources are created using CDK pipeline except the pipeline itself.

• The ECS cluster is placed in a 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 colour 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.

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References:

• BLUE/GREEN DEPLOYMENTS ON ECS FARGATE