Fixing the Dependency Cycle

The error you're seeing is due to a circular dependency in the Terraform configuration. Let me fix that and provide a cost estimate:

Fixed Dependency Cycle

I've fixed the dependency cycle by removing the circular reference between the ECR repository URLs and the application definitions. The key changes were:

1. Removed the container image references from the local.applications map in app_config.tf
2. Updated the ECS module to use the ECR repository URLs directly when creating task definitions

This breaks the circular dependency and should allow Terraform to properly plan and apply the configuration.

Cost Estimate for the Infrastructure

Here's an estimated monthly cost breakdown for running this infrastructure in AWS South Africa (af-south-1) region:

1. ECS Fargate Costs

Development Environment:

• 3 applications + 1 Nginx container = 4 containers
• Each container: 0.25 vCPU, 0.5 GB RAM
• Total: 1 vCPU, 2 GB RAM
• Running 24/7: ~$43.20/month

Production Environment:

• 3 applications + 1 Nginx container = 4 containers
• Each container: 0.5 vCPU, 1 GB RAM
• Total: 2 vCPU, 4 GB RAM
• Running 24/7: ~$86.40/month

2. ECR Storage Costs

• 4 repositories (3 apps + Nginx)
• Assuming 1 GB storage per repository
• ~$4.00/month

3. VPC and Networking Costs

• NAT Gateway: ~$32.40/month
• Elastic IP (if not attached to running instance): ~$3.60/month
• Data transfer: ~$10-20/month (depends on traffic)

4. Route 53 and DNS Costs

• Hosted zone: $0.50/month
• DNS queries: ~$1-5/month (depends on traffic)
• Health checks: ~$2.00/month

5. CloudWatch Logs

• Log storage: ~$5-10/month

Total Estimated Monthly Cost

Development Environment:

• Approximately $100-120/month

Production Environment:

• Approximately $150-180/month

Cost Optimization Tips

1. Use Spot Instances: If your applications can handle interruptions, consider using Spot instances with ECS capacity providers to reduce costs by up to 70%.
2. Scheduled Scaling: If you don't need 24/7 availability for development, schedule the dev environment to run only during business hours to save ~65% on compute costs.
3. Reserved Instances: For production, consider purchasing Fargate Savings Plans for 1 or 3 years to save up to 40%.
4. NAT Gateway Alternatives: Use a NAT instance instead of a NAT Gateway to save ~$30/month.
5. Consolidate Logs: Adjust log retention periods and filter unnecessary logs to reduce CloudWatch costs.

These estimates are based on current AWS pricing and may vary based on actual usage patterns, data transfer, and other factors. The South Africa region tends to be slightly more expensive than some other AWS regions.

Fixing ECS Deployment Rollback Issue

The error you're seeing indicates that your ECS service deployment was automatically rolled back because it couldn't stabilize. This is a safety feature in ECS called the "circuit breaker" that prevents failed deployments from continuing indefinitely.

Common Causes and Solutions

1. Container Health Check Failures

Your containers might be failing health checks or crashing shortly after starting.

Troubleshooting Steps

1. Check Container Logs

First, check the CloudWatch logs for your containers to see why they're failing:

2. Verify Container Images

Make sure your container images exist in ECR and are properly tagged:

3. Test Container Locally

Pull and test your container locally to verify it works:

4. Check Network Configuration

Verify that your security groups allow traffic between the Nginx container and your application containers:

Deployment Strategy Improvements

I've updated your ECS service configuration with:

1. Container Health Checks: Proper health checks to verify container health
2. Logging Configuration: Enhanced logging for better troubleshooting
3. Deployment Configuration: More gradual deployment with circuit breaker settings
4. Health Check Grace Period: Longer grace period to allow containers to start up

Next Steps

1. Apply these Terraform changes
2. Check CloudWatch logs for detailed error information
3. Verify your container images are working correctly

4. If the issue persists, consider:

   • Increasing container memory/CPU
   • Simplifying your application for initial deployment
   • Using the AWS CLI to force a new deployment after fixing issues:

These changes should help stabilize your deployment and provide better visibility into any issues that occur.