Parameters, conditions resources and outputs.

ecsfs_parameters.yaml

Parameters:
  HostedZoneName:
    Type: String
    Description:
      (Optional) If you have a domain available registered with Route 53 you
      can type it (e.g. 'foo.com.'; do not miss the final dot!). Then a DNS
      record gets created on subdomain ecsfs.foo.com which will route to the
      load balancer (the entry point of this application).
Conditions:
  HasHostedZoneName: !Not [ !Equals [ !Ref HostedZoneName, '']]
Resources:
  # Subsequent yaml snippets will fall under this category.
Outputs:
  LoadBalancerDNSName:
    Description: Copy and paste this value into your browser to access the app.
    Value: !GetAtt LoadBalancer.DNSName