Blog Post- Programmatic Cloudformation Template

https://blog.awsmeter.io/programmatic-cloudformation-template/

run following cli to generate cloudformation yml in project root folder.

cd template
sh build.sh

Fragment management

In some case, one AWS resource is used in multiple environments. We can use EJS include features. DEV,QA,PROD cloudformation template can include same resources.

Resources:
<% include ./partials/resources.yml %>
  ...

Variable interpolation

We can interpolate variable from options.json through <%= %> in EJS.

apiTaskDefinition:
   Type: AWS::ECS::TaskDefinition
   DependsOn: ECSTaskRole
   Properties:
     ContainerDefinitions:
     - Name: api
       Essential: true
       Image: <%= container_path %>/api
       Memory: <%= container.api.memory %>
       Environment:
       - Name: REGION
         Value: !Ref "AWS::Region"
     TaskRoleArn: !Ref 'ECSTaskRole'

Loop over list

There is a case we need to loop over all defined instances type(15+ instances) to create spot fleet instance launch configuration.

Properties:
    SpotFleetRequestConfigData:
      IamFleetRole: !GetAtt iamFleetRole.Arn
      SpotPrice: !Ref 'ECSSpotPrice'
      TargetCapacity: !Ref 'DesiredCapacity'
      TerminateInstancesWithExpiration: false
      AllocationStrategy: lowestPrice
      LaunchSpecifications:
      <% for(var i in instancesTypes) {%>
      <% include ./partials/instance-launch-specification.yml %>
      <% } %>