A High-Availability Web App (Udagram) Deployment Using AWS CloudFormation

Deployment Info:

• The create.sh and update.sh scripts create and update the cloudformation stacks respectively.
• The .yaml files contain the cloudformation code, while the correspondingly named .json files contain the template parameters for each stack
• First: udagram-infra* creates the network components for the Udagram web app, including VPC, subnets, gateways, and routing
• Next: udagram-servers* creates the dependent server components, including necessary IAM role and instance profile, Security groups, load balancers, autoscaling group, and servers
• A public S3 bucket containing web files has been configured for static website hosting via the AWS console. The IAM role created in the udagramservers stack permits the private servers to GET S3 objects.
• For debugging purposes, the bastionhost.* files create a bastion host through which an Admin can SSH into the servers in the private subnets.

Deployment Steps:

This assumes that the awscli has been installed and configured with permissions to access an AWS account.

1. Run ./create.sh udagraminfra udagram-infra.yaml udagram-infra-params.json to create a stack named udagraminfra holding the underlying network components.
2. Run ./create.sh udagramservers udagram-servers.yaml udagram-servers-params.json to creata a stack named udagramservers holding the server components.
3. Optionally, run ./create.sh bastionhost bastionhost.yaml bastionhost-params.json to create a stack named bastionhost holding the bastion host server for debugging purposes only. It should be destroyed afterwards.

• Accessing the private servers through the bastion host would require updating the WebServerSecGroup resource in udagram-servers.yaml to allow ingress on port 22 (SSH). In that case, add the following code under SecurityGroupIngress::

  
      - IpProtocol: tcp
        FromPort: 22
        ToPort: 22
        CidrIp: 0.0.0.0/0
  
  

• Save the changes and update the udagramservers stack with: ./update.sh udagramservers udagram-servers.yaml udagram-servers-params.json
• Other stacks can be updated similarly: ./update.sh ...
• After debugging, remove this code from udagram-servers.yaml for security purposes.

Destroying the Deployed Infrastucture

Stacks must be destroyed in reverse order. Wait for the stack deletion to be complete before deleting the underlying stack. Note that stack resources with dependencies cannot be deleted.

1. Run aws cloudformation delete-stack --stack-name bastionhost
2. Run aws cloudformation delete-stack --stack-name udagramservers
3. Run aws cloudformation delete-stack --stack-name udagraminfra