AWSTemplateFormatVersion: 2010-09-09
Description: >-
  AWS CloudFormation Sample Template. Create a multi-az, load balanced and auto-scaled 
  sample web site running on an Apache Web Server. The application is configured to span all Availability Zones in
  the region and is auto-scaled based on the CPU utilization of the web servers.
  Notifications will be sent to the operator email address on scaling events.
  The instances are load balanced with a simple health check against the default
  web page. **WARNING** This template creates one or more Amazon EC2 instances
  and an Elastic Load Balancer. You will be billed for the AWS resources used if
  you create a stack from this template.

Resources:
  NotificationTopic:
    Type: 'AWS::SNS::Topic'
    Properties:
      Subscription:
        - Endpoint: !Ref OperatorEMail
          Protocol: email
  WebServerGroup:
    Type: 'AWS::AutoScaling::AutoScalingGroup'
    Properties:
      VPCZoneIdentifier:
        - !Ref PrivateSubnet1ID
        - !Ref PrivateSubnet2ID
      LaunchConfigurationName: !Ref LaunchConfig
      MinSize: '1'
      MaxSize: '3'
      LoadBalancerNames:
        - !Ref ElasticLoadBalancer
      NotificationConfiguration:
        TopicARN: !Ref NotificationTopic
        NotificationTypes:
          - 'autoscaling:EC2_INSTANCE_LAUNCH'
          - 'autoscaling:EC2_INSTANCE_LAUNCH_ERROR'
          - 'autoscaling:EC2_INSTANCE_TERMINATE'
          - 'autoscaling:EC2_INSTANCE_TERMINATE_ERROR'
    CreationPolicy:
      ResourceSignal:
        Timeout: PT15M
        Count: '1'
    UpdatePolicy:
      AutoScalingRollingUpdate:
        MinInstancesInService: '1'
        MaxBatchSize: '1'
        PauseTime: PT15M
        WaitOnResourceSignals: 'true'
  LaunchConfig:
    Type: 'AWS::AutoScaling::LaunchConfiguration'
    Metadata:
      Comment: Install a simple application
      'AWS::CloudFormation::Init':
        config:
          packages:
            yum:
              httpd: []
          files:
            /var/www/html/index.html:
              content: !Join 
                - |+

                - - >-
                    <h1>Congratulations, you have successfully launched the AWS
                    CloudFormation sample.</h1>
              mode: '000644'
              owner: root
              group: root
            /etc/cfn/cfn-hup.conf:
              content: !Join 
                - ''
                - - |
                    [main]
                  - stack=
                  - !Ref 'AWS::StackId'
                  - |+

                  - region=
                  - !Ref 'AWS::Region'
                  - |+

              mode: '000400'
              owner: root
              group: root
            /etc/cfn/hooks.d/cfn-auto-reloader.conf:
              content: !Join 
                - ''
                - - |
                    [cfn-auto-reloader-hook]
                  - |
                    triggers=post.update
                  - >
                    path=Resources.LaunchConfig.Metadata.AWS::CloudFormation::Init
                  - 'action=/opt/aws/bin/cfn-init -v '
                  - '         --stack '
                  - !Ref 'AWS::StackName'
                  - '         --resource LaunchConfig '
                  - '         --region '
                  - !Ref 'AWS::Region'
                  - |+

                  - |
                    runas=root
          services:
            sysvinit:
              httpd:
                enabled: 'true'
                ensureRunning: 'true'
              cfn-hup:
                enabled: 'true'
                ensureRunning: 'true'
                files:
                  - /etc/cfn/cfn-hup.conf
                  - /etc/cfn/hooks.d/cfn-auto-reloader.conf
    Properties:
      KeyName: !Ref KeyName
      ImageId: !FindInMap 
        - AWSRegionArch2AMI
        - !Ref 'AWS::Region'
        - !FindInMap 
          - AWSInstanceType2Arch
          - !Ref InstanceType
          - Arch
      SecurityGroups:
        - !GetAtt InstanceSecurityGroup.GroupId
      InstanceType: !Ref InstanceType
      UserData: !Base64 
        'Fn::Join':
          - ''
          - - |
              #!/bin/bash -xe
            - |
              yum update -y aws-cfn-bootstrap
            - '/opt/aws/bin/cfn-init -v '
            - '         --stack '
            - !Ref 'AWS::StackName'
            - '         --resource LaunchConfig '
            - '         --region '
            - !Ref 'AWS::Region'
            - |+

            - '/opt/aws/bin/cfn-signal -e $? '
            - '         --stack '
            - !Ref 'AWS::StackName'
            - '         --resource WebServerGroup '
            - '         --region '
            - !Ref 'AWS::Region'
            - |+

  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'
  CPUAlarmHigh:
    Type: 'AWS::CloudWatch::Alarm'
    Properties:
      AlarmDescription: Scale-up if CPU > 90% for 10 minutes
      MetricName: CPUUtilization
      Namespace: AWS/EC2
      Statistic: Average
      Period: '300'
      EvaluationPeriods: '2'
      Threshold: '90'
      AlarmActions:
        - !Ref WebServerScaleUpPolicy
      Dimensions:
        - Name: AutoScalingGroupName
          Value: !Ref WebServerGroup
      ComparisonOperator: GreaterThanThreshold
  CPUAlarmLow:
    Type: 'AWS::CloudWatch::Alarm'
    Properties:
      AlarmDescription: Scale-down if CPU < 70% for 10 minutes
      MetricName: CPUUtilization
      Namespace: AWS/EC2
      Statistic: Average
      Period: '300'
      EvaluationPeriods: '2'
      Threshold: '70'
      AlarmActions:
        - !Ref WebServerScaleDownPolicy
      Dimensions:
        - Name: AutoScalingGroupName
          Value: !Ref WebServerGroup
      ComparisonOperator: LessThanThreshold
  ElasticLoadBalancer:
    Type: 'AWS::ElasticLoadBalancing::LoadBalancer'
    Properties:
      Subnets:
        - !Ref PublicSubnet1ID
        - !Ref PublicSubnet2ID
      CrossZone: 'true'
      Listeners:
        - LoadBalancerPort: '80'
          InstancePort: '80'
          Protocol: HTTP
      HealthCheck:
        Target: 'HTTP:80/'
        HealthyThreshold: '3'
        UnhealthyThreshold: '5'
        Interval: '30'
        Timeout: '5'
      SecurityGroups:
        - !GetAtt LoadBalancerSecurityGroup.GroupId
  InstanceSecurityGroup:
    Type: 'AWS::EC2::SecurityGroup'
    Properties:
      GroupDescription: Enable SSH access and HTTP from the load balancer only
      SecurityGroupIngress:
        - IpProtocol: tcp
          FromPort: 22
          ToPort: 22
          CidrIp: !Ref SSHLocation
        - IpProtocol: tcp
          FromPort: 80
          ToPort: 80
          SourceSecurityGroupId: !GetAtt LoadBalancerSecurityGroup.GroupId
      VpcId: !Ref VPCID
  LoadBalancerSecurityGroup:
    Type: 'AWS::EC2::SecurityGroup'
    Properties:
      GroupDescription: Enable HTTP from the world
      SecurityGroupIngress:
        - IpProtocol: tcp
          FromPort: 80
          ToPort: 80
          CidrIp: 0.0.0.0/0
      VpcId: !Ref VPCID