Zero Downtime Deployment with Terraform: Implementing Blue-Green Strategy on AWS

Scenario: Imagine you need to deploy a new version of an application on AWS with zero downtime using Terraform. How would you implement a blue-green deployment strategy to accomplish this?

When updating applications on AWS, ensuring zero downtime is crucial for maintaining a seamless user experience. In this guide, we delve into the implementation of a blue-green deployment strategy using Terraform to achieve this goal.

Here’s how it might look conceptually:

1. Initial Setup:
   • Define two environments, “blue” and “green,” each with its own set of AWS resources, such as EC2 instances, configured identically.
   • Use Terraform to provision both environments, but route traffic only to the “blue” environment initially.
     
     We start by defining two identical environments named “blue” and “green.” Each has its AWS resources, like EC2 instances, set up identically. Initially, the “blue” environment handles all live traffic.
     
2. Deployment:
   • When a new version of your application is ready, update the “green” environment with the new version using Terraform.
   • Perform all necessary tests on the “green” environment to ensure the new version is ready for production.
     
     Upon preparing a new application version, we apply the update to the “green” environment using Terraform. Thorough testing in the “green” environment ensures that the application is ready for production.
     
3. Traffic Switching:
   • After testing, modify the load balancer settings using Terraform to route traffic from the “blue” environment to the “green” environment.
   • Monitor the “green” environment to ensure it handles the traffic as expected.
     
     Successful testing leads to the crucial step of traffic switching. This is where we modify the load balancer settings through Terraform to redirect traffic from “blue” to “green.”
     
4. Clean Up:
   • Once you’re confident that the “green” environment is stable, the “blue” environment can be either destroyed, kept on standby for the next deployment, or updated to the new version in preparation for the next switch.
     
     After the transition, we focus on the clean-up process. The “green” environment now becomes the primary, and the “blue” environment is either decommissioned, put on standby, or updated to serve as the next staging area.

A Real-World UseCase

Creating a complete Terraform template for a blue-green deployment involves several AWS services and a careful orchestration of resources. Below, I’ll provide a simplified but comprehensive Terraform example that includes:

• An Elastic Load Balancer (ELB) to manage incoming traffic.
• Two Auto Scaling Groups (ASGs), representing the blue and green environments.
• Launch Configurations for each ASG, which define the EC2 instances’ properties.

Please note: This is a conceptual example and might require adjustments to fit specific use cases. For instance, your application’s architecture, VPC settings, security groups, IAM roles, and health check configurations will need to be tailored to your environment.

Explore the Terraform Manifest

To help visualize this process, I’ve created a detailed Terraform template, which includes an Elastic Load Balancer (ELB) and two Auto Scaling Groups (ASGs) for both environments. Each ASG has its corresponding Launch Configurations that define the EC2 instances’ specifics.
For those looking to implement this strategy, I’ve shared a comprehensive Terraform manifest on my GitHub repository. This manifest serves as a practical reference for setting up a blue-green deployment.

Visit the GitHub❤️ExamNative Repository for the Complete Terraform Manifest

I encourage you to explore this manifest and tailor it to your specific needs. If you find the resources valuable, please consider starring the repository and sharing it with others who might benefit from it.