faheem556 / aws-blue-green-tomcat

Scenario: Update Java application (WAR) on Tomcat servers with zero downtime on AWS

Solution Highlights:

1. A sample Java WAR application with /health endpoint
2. A bash script to upload java web archives to S3 bucket
3. Terraform script to deploy and upgrade the application on VMs in AWS
4. Zero-downtime upgrades using weighted forwarding in target groups
5. Application health check validation for readiness and liveliness
6. Blue/green launch configs and auto-scalling groups to demonstrate immutable infra
7. Automated ASG scaling based on canary/BG deployment style

Sample App

Run Locally

cd app
# Build and run WAR setup (tomcat+war)

docker build -t funfact:java-war-1.0 -f Dockerfile.tomcat .
docker run -d -p 8080:8080 funfact:java-war-1.0

# Test runnging app
open http://localhost:8080
curl http://localhost:8080/health

Build

cd app
mvn package -Pwar

# No tests
mvn package -Pwar -Dmaven.test.skip=true -Dcheckstyle.skip=true -Dmaven.javadoc.skip=true --fail-never

Upload

./scripts/upload.sh \
  -b bucket \
  -w ./app/target/FunfactApplication.war \
  -v 1.1.0 \
  -n funfact.war

Terraform

Setup Infra

cd terraform
terraform init -backend-config=./backend.tfvars
terraform validate
terraform plan -var "traffic_distribution=blue" -out tfplan
terraform apply tfplan

The script should spit out the public DNS. Validate app comes up correctly with 100% traffic going to the blue environment.

Upgrade the app

1. Update terraform.tfvars blue/green archive values as needed.

2. Apply terraform scripts for gradual roll-out (pipeline-steps)

cd terraform
terraform init -backend-config=./backend.tfvars
terraform plan -var "traffic_distribution=blue-90" -out tfplan
terraform apply tfplan

# Validate that 10% traffic is going to the new app

terraform plan -var "traffic_distribution=split" -out tfplan
terraform apply tfplan

# Validate that 50% traffic is going to the new app

terraform plan -var "traffic_distribution=green" -out tfplan
terraform apply tfplan

# Validate that 100% traffic is going to the new app

3. Flip the blue/green variable values in the next upgrade cycle