app.json

{
    "AWSTemplateFormatVersion" : "2010-09-09",
    "Description": "VPC cloudformation template",
    "Outputs": {
        "LoadBalancerDNSName": {
            "Description" : "ELB DNS Name",
            "Value": { "Fn::GetAtt" : [ "MyAppServerELB", "DNSName" ] }
        }
    },
    "Parameters": {
        "Stage": {
            "Type": "String",
            "AllowedValues" : [ "CODE", "PROD" ],
            "Default" : "CODE"
        },
        "CidrA": {
            "Type": "String"
        },
        "CidrB": {
            "Type": "String"
        },
        "CidrC": {
            "Type": "String"
        },
        "SubnetA": {
            "Type": "String"
        },
        "SubnetB": {
            "Type": "String"
        },
        "SubnetC": {
            "Type": "String"
        },
        "DefaultSecGroup": {
            "Type": "String"
        },
        "AppPort": {
            "Type": "Number"
        },
        "InstanceType": {
            "Type": "String",
            "Default": "m1.small"
        },
    },
    "Resources": {
        "MyAppServerELB" : {
            "Type": "AWS::ElasticLoadBalancing::LoadBalancer",
            "Properties": {
                "AvailabilityZones" :  { "Fn::GetAZs" : ""},
            }
        },
        "MyAppServerSecurityGroup" : {
            "Type" : "AWS::EC2::SecurityGroup",
            "Properties" : {
                "GroupDescription" : "Monkey",
                "SecurityGroupIngress" : [
                {
                    "IpProtocol" : "tcp", 
                    "FromPort" : { "Ref": "AppPort" },
                    "ToPort" : { "Ref": "AppPort" },
                    "SourceSecurityGroupOwnerId" : {"Fn::GetAtt" : ["MyAppServerELB", "SourceSecurityGroup.OwnerAlias"]},
                    "SourceSecurityGroupName" : {"Fn::GetAtt" : ["MyAppServerELB", "SourceSecurityGroup.GroupName"]}

                } ]
            }
        },
        "MyAppServerLaunchConfig" : {
            "Type" : "AWS::AutoScaling::LaunchConfiguration",
            "Properties" : {
                "ImageId" : "ami-6411e20d",
                "SecurityGroups" : [ { "Ref" : "MyAppServerSecurityGroup" }, { "Ref": "DefaultSecGroup" } ],
                "InstanceType" : { "Ref": "InstanceType" }
            }
        },
        "MyAppServerGroup" : {
            "Type" : "AWS::AutoScaling::AutoScalingGroup",
            "Properties" : {
                "AvailabilityZones" : { "Fn::GetAZs" : ""},
                "LaunchConfigurationName" : { "Ref" : "MyAppServerLaunchConfig" },
                "MinSize" : "1",
                "MaxSize" : "3",
                "LoadBalancerNames" : [ { "Ref" : "MyAppServerELB" } ]
            }
        }
    }
}