Mockup for a DSL to generate Amazon CloudFormation configurations

cfn_dsl_mockup.rb

# Based on half of https://s3.amazonaws.com/cloudformation-templates-us-east-1/WordPress-1.0.0.template
# Methods beginning with a lowercase letter are 'native' and have special behaviour.
# Methods beginning with an uppercase letter get literally transformed into JSON

templates do
  Alarm do
    EvaluationPeriods 1
    Statistic 'Average'
    Period 60
    AlarmActions: ref('AlarmTopic')
    Namespace "AWS/EC2"
    InsufficientDataActions ref('AlarmTopic')
  end    
end

cloud_formation do
  Description "WordPress is web software you can use to create a beautiful website or blog. This template creates a scalable WordPress installation using an Auto Scaling group behind an Elastic Load Balancer along with an Amazon Relational Database Service database instance to store the content."
  
  parameters do
    KeyName "Name of an existing EC2 KeyPair to enable SSH access into the WordPress web server"
    WordPressDBName "The WordPress database name", 'wordpress'
    WordPressUser "The WordPress database admin account user", "admin", :noecho => true
    WordPressPwd "The WordPress database admin account password", "admin", :noecho => true
    GroupSize "The initial number of EC2 instances for the WordPress web server", '1'
    InstanceType "The type of EC2 instances used for the WordPress web server", 'm1.small'
    OperatorEmail "Email address to notify if there are any operational issues", "nobody@amazon.com"
    WordPressDBPort "TCP/IP port for the WordPress database", '8443'
    WebServerPort "TCP/IP port for the WordPress web server", '8443'
  end
  
  resources do
    CPUAlarmHigh 'AWS::CloudWatch::Alarm' do
      merge Alarm
      Threshhold 10
      AlarmDescription "Alarm if CPU too high or metric disappears indicating instance is down"
      Dimensions :name => 'AutoScalingGroupName', :value => ref('WebServerGroup')
      ComparisonOperator "GreaterThanThreshold"
      MetricName "CPUUtilization"
    end
    
    TooManyUnhealthyHostsAlarm 'AWS::CloudWatch::Alarm' do
      merge Alarm
      Threshold "0"
      Dimensions :name => "LoadBalancerName", :value => ref('ElasticLoadBalancer')
      ComparisonOperator "GreaterThanThreshold"
      MetricName "UnHealthyHostCount"
    end
    
    EC2SecurityGroup 'AWS::EC2::SecurityGroup' do
      SecurityGroupIngress [
        {:FromPort => 22, :CidrIp => '0.0.0.0/0', :ToPort => 22, :IpProtocol => 'tcp'},
        {:FromPort => ref('WebServerPort'), :CidrIp => '0.0.0.0/0', :ToPort => ref('WebServerPort'), :IpProtocol => 'tcp'},
      ]
      GroupDescription "HTTP and SSH access"
    end
      
    RequestLatencyAlarmHigh 'AWS::CloudWatch::Alarm' do
      merge Alarm
      Threshold 1
      AlarmDescription "Alarm if there aren't any requests coming through."
      Dimensions :name => "LoadBalancerName", :value => ref('ElasticLoadBalancer')
      ComparisonOperator "GreaterThanThreshold"
      MetricName "Latency"
    end
    
    ElasticLoadBalancer 'AWS::ElasticLoadBalancing::LoadBalancer' do
      Listeners [
        lambda do
          InstancePort ref('WebServerPort')
          PolicyNames ['p1']
          Protocol 'HTTP'
          LoadBalancerPort '80'
        end
      ]
      HealthCheck do
        HealthyThreshold 2
        Timeout 5
        Interval 10
        UnhealthyThreshold 5
        Target ['HTTP://', ref('WebServerPort'), '/wp-admin/install.php'].fn_join('')
      end
      AvailabilityZones fn_GetAZs(ref('AWS::Region'))
      LBCookieSticknessPolicy [
        lambda do
          CookieExpirationPeriod 30
          PolicyName 'p1'
        end
      ]
    end
  end
end