blue-green-deployments

## What I do - Implement blue-green deployment strategies for zero-downtime releases - Manage parallel production environments (blue = active, green = standby) - Coordinate traffic switching between environments - Design rollback mechanisms for rapid recovery - Automate the entire blue-green deployment workflow - Monitor both environments during and after deployment ## When to use me - When you need zero-downtime deployments for critical applications - When you want to validate new releases in production-like environments - When rapid rollback capability is a requirement - When deploying applications that can't tolerate rolling updates - When you need to test infrastructure changes alongside application changes - When compliance requires production-like testing before full rollout ## Key Concepts ### Architecture Overview ``` ┌─────────────────┐ ┌─────────────────┐ │ Load Balancer │ │ Load Balancer │ │ (Active Blue) │ │ (Standby Green)│ └────────┬────────┘ └────────┬────────┘ │ │ ┌────▼────┐ ┌────▼────┐ │ Blue │ │ Green │ │ v1.0 │ │ v1.1 │ │ (Live) │◄──Switch───►│ (Test) │ └─────────┘ └─────────┘ ``` ### Implementation with Docker Compose ```yaml # docker-compose.blue.yml services: app: image: myapp:blue ports: - "8080:8080" # docker-compose.green.yml services: app: image: myapp:green ports: - "8081:8080" ``` ### Traffic Switching Script ```bash #!/bin/bash # Switch traffic from blue to green # Health check green environment if curl -sf http://green.example.com/health > /dev/null; then # Update load balancer to point to green aws elbv2 modify-listener \ --listener-arn $LISTENER_ARN \ --default-actions Type=forward,TargetGroupArn=$GREEN_TARGET_GROUP echo "Traffic switched to green environment" # Keep blue running for rollback echo "Blue environment preserved for rollback" else echo "Green environment health check failed" exit 1 fi ``` ### Key Benefits - **Instant Rollback**: Switch back to previous version in seconds - **Zero Downtime**: Users experience no interruption during deployment - **Full Testing**: Validate new version in production before full rollout - **Environment Parity**: Both environments use identical infrastructure - **Risk Mitigation**: Isolate deployment risks from users ### Important Considerations - Both environments must be fully provisioned and ready - Database schema changes require careful backward compatibility planning - Session state management must work across both environments - Consider cost implications of running two complete environments - Implement proper health checks before and after switching traffic