{
  "AWSTemplateFormatVersion" : "2010-09-09",

  "Description" : "AWS CloudFormation Sample Template",

  "Parameters" : {

    "KeyName" : {
      "Description" : "Name of an existing EC2 KeyPair to enable SSH access to the instances",
      "Type" : "String"
    },

    "InstanceType" : {
      "Description" : "WebServer EC2 instance type",
      "Type" : "String",
      "Default" : "m1.small",
      "AllowedValues" : [ "t1.micro","m1.small","m1.medium","m1.large"],
      "ConstraintDescription" : "must be a valid EC2 instance type."
    },

    "DBName": {
      "Default": "wordpress",
      "Description" : "The WordPress database name",
      "Type": "String",
      "MinLength": "1",
      "MaxLength": "64",
      "AllowedPattern" : "[a-zA-Z][a-zA-Z0-9]*",
      "ConstraintDescription" : "must begin with a letter and contain only alphanumeric characters."
    },

    "DBUsername": {
      "Default": "admin",
      "NoEcho": "true",
      "Description" : "The WordPress database admin account username",
      "Type": "String",
      "MinLength": "1",
      "MaxLength": "16",
      "AllowedPattern" : "[a-zA-Z][a-zA-Z0-9]*",
      "ConstraintDescription" : "must begin with a letter and contain only alphanumeric characters."
    },

    "DBPassword": {
      "Default": "admin",
      "NoEcho": "true",
      "Description" : "The WordPress database admin account password",
      "Type": "String",
      "MinLength": "1",
      "MaxLength": "41",
      "AllowedPattern" : "[a-zA-Z0-9]*",
      "ConstraintDescription" : "must contain only alphanumeric characters."
    },

    "DBRootPassword": {
      "Default": "admin",
      "NoEcho": "true",
      "Description" : "Root password for MySQL",
      "Type": "String",
      "MinLength": "1",
      "MaxLength": "41",
      "AllowedPattern" : "[a-zA-Z0-9]*",
      "ConstraintDescription" : "must contain only alphanumeric characters."
    }
  },

  "Resources" : {
    "WebServerGroup" : {
      "Type" : "AWS::AutoScaling::AutoScalingGroup",
      "Properties" : {
        "AvailabilityZones" : { "Fn::GetAZs" : ""},
        "LaunchConfigurationName" : { "Ref" : "LaunchConfig" },
        "MinSize" : "1",
        "MaxSize" : "3",
        "LoadBalancerNames" : [ { "Ref" : "ElasticLoadBalancer" } ]
      }
    },

    "WebServerScaleUpPolicy" : {
      "Type" : "AWS::AutoScaling::ScalingPolicy",
      "Properties" : {
        "AdjustmentType" : "ChangeInCapacity",
        "AutoScalingGroupName" : { "Ref" : "WebServerGroup" },
        "Cooldown" : "60",
        "ScalingAdjustment" : "1"
      }
    },

    "WebServerScaleDownPolicy" : {
      "Type" : "AWS::AutoScaling::ScalingPolicy",
      "Properties" : {
        "AdjustmentType" : "ChangeInCapacity",
        "AutoScalingGroupName" : { "Ref" : "WebServerGroup" },
        "Cooldown" : "60",
        "ScalingAdjustment" : "-1"
      }
    },

    "MEMAlarmHigh": {
     "Type": "AWS::CloudWatch::Alarm",
     "Properties": {
        "AlarmDescription": "Scale-up if MEM > 90% for 10 minutes",
        "MetricName": "MemoryUtilization",
        "Namespace": "system/linux",
        "Statistic": "Average",
        "Period": "60",
        "EvaluationPeriods": "1",
        "Threshold": "50",
        "AlarmActions": [ { "Ref": "WebServerScaleUpPolicy" } ],
        "Dimensions": [
          {
            "Name": "AutoScalingGroupName",
            "Value": { "Ref": "WebServerGroup" }
          }
        ],
        "ComparisonOperator": "GreaterThanThreshold"
      }
    },
    "MEMAlarmLow": {
     "Type": "AWS::CloudWatch::Alarm",
     "Properties": {
        "AlarmDescription": "Scale-down if MEM < 70% for 10 minutes",
        "MetricName": "MemoryUtilization",
        "Namespace": "system/linux",
        "Statistic": "Average",
        "Period": "60",
        "EvaluationPeriods": "1",
        "Threshold": "15",
        "AlarmActions": [ { "Ref": "WebServerScaleDownPolicy" } ],
        "Dimensions": [
          {
            "Name": "AutoScalingGroupName",
            "Value": { "Ref": "WebServerGroup" }
          }
        ],
        "ComparisonOperator": "LessThanThreshold"
      }
    },

    "ElasticLoadBalancer" : {
      "Type" : "AWS::ElasticLoadBalancing::LoadBalancer",
      "Properties" : {
        "AvailabilityZones" : { "Fn::GetAZs" : "" },
        "Listeners" : [ {
          "LoadBalancerPort" : "80",
          "InstancePort" : "80",
          "Protocol" : "HTTP"
        } ],
        "HealthCheck" : {
          "Target" : "HTTP:80/",
          "HealthyThreshold" : "3",
          "UnhealthyThreshold" : "5",
          "Interval" : "30",
          "Timeout" : "5"
        }
      }
    },

    "LaunchConfig" : {
      "Type" : "AWS::AutoScaling::LaunchConfiguration",
      "Metadata" : {
        "AWS::CloudFormation::Init" : {
          "config" : {
            "files" : {
              "/tmp/setup.mysql" : {
                "content" : { "Fn::Join" : ["", [
                "CREATE DATABASE ", { "Ref" : "DBName" }, ";\n",
                "GRANT ALL PRIVILEGES ON ", { "Ref" : "DBName" },
                ".* TO '", { "Ref" : "DBUsername" }, "'@'localhost'\n",
                "IDENTIFIED BY '", { "Ref" : "DBPassword" }, "';\n",
                "FLUSH PRIVILEGES;\n",
                "EXIT\n"
                  ]]},
                "mode"  : "000644",
                "owner" : "root",
                "group" : "root"
              },
              "/tmp/stats-crontab.txt" : {
                "content" : { "Fn::Join" : ["", [
                "MAIL=\"\"\n",
                "\n",
                "* * * * * /opt/aws/bin/cfn-push-stats --watch ",
                { "Ref" : "MEMAlarmHigh" }, " --mem-util\n",
                "* * * * * /opt/aws/bin/cfn-push-stats --watch ",
                { "Ref" : "MEMAlarmLow" }, " --mem-util\n"
                ]]},
                "mode"    : "000600",
                "owner"   : "root",
                "group"   : "root"
              }
            },
            "packages" : {
              "yum" : {
                "python-psutil": [],
                "cronie"       : [],
                "mysql"        : [],
                "mysql-server" : [],
                "httpd"        : [],
                "wordpress"    : []
              }
            },
            "services" : {
              "systemd" : {
                "mysqld"   : { "enabled" : "true", "ensureRunning" : "true" },
                "httpd"    : { "enabled" : "true", "ensureRunning" : "true" },
                "crond"    : { "enabled" : "true", "ensureRunning" : "true" }
              }
            }
          }
        }
      },
      "Properties": {
        "ImageId" : "F16-x86_64-cfntools",
        "InstanceType"   : { "Ref" : "InstanceType" },
        "KeyName"        : { "Ref" : "KeyName" },
        "UserData"       : { "Fn::Base64" : { "Fn::Join" : ["", [
          "#!/bin/bash -v\n",
          "/opt/aws/bin/cfn-init -s ", { "Ref" : "AWS::StackName" },
          " -r LaunchConfig ",
          " --region ", { "Ref" : "AWS::Region" }, "\n",

          "# Setup MySQL root password and create a user\n",
          "mysqladmin -u root password '", { "Ref" : "DBRootPassword" }, "'\n",

          "mysql -u root --password='", { "Ref" : "DBRootPassword" },
          "' < /tmp/setup.mysql\n",

          "sed --in-place --e s/database_name_here/", { "Ref" : "DBName" },
          "/ --e s/username_here/", { "Ref" : "DBUsername" },
          "/ --e s/password_here/", { "Ref" : "DBPassword" },
          "/ /usr/share/wordpress/wp-config.php\n",

          "# install crontab\n",
          "crontab /tmp/stats-crontab.txt\n"
        ]]}}
      }
    }
  },

  "Outputs" : {
    "URL" : {
      "Description" : "The URL of the website",
      "Value" :  { "Fn::Join" : [ "", [ "http://", { "Fn::GetAtt" : [ "ElasticLoadBalancer", "DNSName" ]}]]}
    }
  }
}