AWSTemplateFormatVersion: '2010-09-09'
Description: EC2 ECS cluster running containers in a private subnet. Supports
             public facing load balancers, private internal load balancers, and
             both internal and external service discovery namespaces. Two AZs.
Parameters:
  EnvironmentName:
    Type: String
    Description: "A friendly environment name that will be used for namespacing all cluster resources. Example: staging, qa, or production"
  InstanceType:
    Description: EC2 instance type
    Type: String
    Default: t3.medium
    Description: Class of EC2 instance used to host containers. Choose t3 for testing, m5 for general purpose, c5 for CPU intensive services, and r5 for memory intensive services
    AllowedValues: [ t3.micro, t3.small, t3.medium, t3.large, t3.xlarge, t3.2xlarge,
     m5.large, m5.xlarge, m5.2large, m5.4xlarge, m5.12xlarge, m5.24large,
     c5.large, c5.xlarge, c5.2xlarge, c5.4xlarge, c5.9xlarge, c5.18xlarge,
     r5.large, r5.xlarge, r5.2xlarge, r5.4xlarge, r5.12xlarge, r5.24xlarge ]
    ConstraintDescription: Please choose a valid instance type.
  DesiredCapacity:
    Type: Number
    Default: '2'
    Description: Number of EC2 instances to launch in your ECS cluster.
  MaxSize:
    Type: Number
    Default: '6'
    Description: Maximum number of EC2 instances that can be launched in your ECS cluster.
  ECSAMI:
    Description: AMI ID
    Type: AWS::SSM::Parameter::Value<AWS::EC2::Image::Id>
    Default: /aws/service/ecs/optimized-ami/amazon-linux-2/recommended/image_id
    Description: The Amazon Machine Image ID used for the cluster, leave it as the default value to get the latest AMI

Mappings:
  # Hard values for the subnet masks. These masks define
  # the range of internal IP addresses that can be assigned.
  # The VPC can have all IP's from 10.0.0.0 to 10.0.255.255
  # There are four subnets which cover the ranges:
  #
  # 10.0.0.0 - 10.0.0.255
  # 10.0.1.0 - 10.0.1.255
  # 10.0.2.0 - 10.0.2.255
  # 10.0.3.0 - 10.0.3.255
  #
  # If you need more IP addresses (perhaps you have so many
  # instances that you run out) then you can customize these
  # ranges to add more
  SubnetConfig:
    VPC:
      CIDR: '10.0.0.0/16'
    PublicOne:
      CIDR: '10.0.0.0/24'
    PublicTwo:
      CIDR: '10.0.1.0/24'
    PrivateOne:
      CIDR: '10.0.100.0/24'
    PrivateTwo:
      CIDR: '10.0.101.0/24'
Resources:
  # VPC in which containers will be networked.
  # It has two public subnets, and two private subnets.
  # We distribute the subnets across the first two available subnets
  # for the region, for high availability.
  VPC:
    Type: AWS::EC2::VPC
    Properties:
      EnableDnsSupport: true
      EnableDnsHostnames: true
      CidrBlock: !FindInMap ['SubnetConfig', 'VPC', 'CIDR']
      Tags:
        - Key: Name
          Value: !Ref EnvironmentName

  # Two public subnets, where containers can have public IP addresses
  PublicSubnetOne:
    Type: AWS::EC2::Subnet
    Properties:
      AvailabilityZone: !Select
        - 0
        - Fn::GetAZs: !Ref 'AWS::Region'
      VpcId: !Ref 'VPC'
      CidrBlock: !FindInMap ['SubnetConfig', 'PublicOne', 'CIDR']
      MapPublicIpOnLaunch: true
  PublicSubnetTwo:
    Type: AWS::EC2::Subnet
    Properties:
      AvailabilityZone: !Select
        - 1
        - Fn::GetAZs: !Ref 'AWS::Region'
      VpcId: !Ref 'VPC'
      CidrBlock: !FindInMap ['SubnetConfig', 'PublicTwo', 'CIDR']
      MapPublicIpOnLaunch: true

  # Two private subnets where containers will only have private
  # IP addresses, and will only be reachable by other members of the
  # VPC
  PrivateSubnetOne:
    Type: AWS::EC2::Subnet
    Properties:
      AvailabilityZone: !Select
        - 0
        - Fn::GetAZs: !Ref 'AWS::Region'
      VpcId: !Ref 'VPC'
      CidrBlock: !FindInMap ['SubnetConfig', 'PrivateOne', 'CIDR']
  PrivateSubnetTwo:
    Type: AWS::EC2::Subnet
    Properties:
      AvailabilityZone: !Select
        - 1
        - Fn::GetAZs: !Ref 'AWS::Region'
      VpcId: !Ref 'VPC'
      CidrBlock: !FindInMap ['SubnetConfig', 'PrivateTwo', 'CIDR']

  # Setup networking resources for the public subnets. Containers
  # in the public subnets have public IP addresses and the routing table
  # sends network traffic via the internet gateway.
  InternetGateway:
    Type: AWS::EC2::InternetGateway
  GatewayAttachment:
    Type: AWS::EC2::VPCGatewayAttachment
    Properties:
      VpcId: !Ref 'VPC'
      InternetGatewayId: !Ref 'InternetGateway'
  PublicRouteTable:
    Type: AWS::EC2::RouteTable
    Properties:
      VpcId: !Ref 'VPC'
  PublicRoute:
    Type: AWS::EC2::Route
    DependsOn: GatewayAttachment
    Properties:
      RouteTableId: !Ref 'PublicRouteTable'
      DestinationCidrBlock: '0.0.0.0/0'
      GatewayId: !Ref 'InternetGateway'
  PublicSubnetOneRouteTableAssociation:
    Type: AWS::EC2::SubnetRouteTableAssociation
    Properties:
      SubnetId: !Ref PublicSubnetOne
      RouteTableId: !Ref PublicRouteTable
  PublicSubnetTwoRouteTableAssociation:
    Type: AWS::EC2::SubnetRouteTableAssociation
    Properties:
      SubnetId: !Ref PublicSubnetTwo
      RouteTableId: !Ref PublicRouteTable

  # Setup networking resources for the private subnets. Containers
  # in these subnets have only private IP addresses, and must use a NAT
  # gateway to talk to the internet. We launch two NAT gateways, one for
  # each private subnet.
  NatGatewayOneAttachment:
    Type: AWS::EC2::EIP
    DependsOn: GatewayAttachment
    Properties:
        Domain: vpc
  NatGatewayTwoAttachment:
    Type: AWS::EC2::EIP
    DependsOn: GatewayAttachment
    Properties:
        Domain: vpc
  NatGatewayOne:
    Type: AWS::EC2::NatGateway
    Properties:
      AllocationId: !GetAtt NatGatewayOneAttachment.AllocationId
      SubnetId: !Ref PublicSubnetOne
  NatGatewayTwo:
    Type: AWS::EC2::NatGateway
    Properties:
      AllocationId: !GetAtt NatGatewayTwoAttachment.AllocationId
      SubnetId: !Ref PublicSubnetTwo
  PrivateRouteTableOne:
    Type: AWS::EC2::RouteTable
    Properties:
      VpcId: !Ref 'VPC'
  PrivateRouteOne:
    Type: AWS::EC2::Route
    Properties:
      RouteTableId: !Ref PrivateRouteTableOne
      DestinationCidrBlock: 0.0.0.0/0
      NatGatewayId: !Ref NatGatewayOne
  PrivateRouteTableOneAssociation:
    Type: AWS::EC2::SubnetRouteTableAssociation
    Properties:
      RouteTableId: !Ref PrivateRouteTableOne
      SubnetId: !Ref PrivateSubnetOne
  PrivateRouteTableTwo:
    Type: AWS::EC2::RouteTable
    Properties:
      VpcId: !Ref 'VPC'
  PrivateRouteTwo:
    Type: AWS::EC2::Route
    Properties:
      RouteTableId: !Ref PrivateRouteTableTwo
      DestinationCidrBlock: 0.0.0.0/0
      NatGatewayId: !Ref NatGatewayTwo
  PrivateRouteTableTwoAssociation:
    Type: AWS::EC2::SubnetRouteTableAssociation
    Properties:
      RouteTableId: !Ref PrivateRouteTableTwo
      SubnetId: !Ref PrivateSubnetTwo


  # ECS Resources
  ECSCluster:
    Type: AWS::ECS::Cluster
    Properties:
      ClusterName: !Ref EnvironmentName

  # A security group for the containers we will run in ECS.
  # Rules are added to this security group based on what ingress you
  # add for the cluster.
  ContainerSecurityGroup:
    Type: AWS::EC2::SecurityGroup
    Properties:
      GroupDescription: Access to the ECS hosts that run containers
      VpcId: !Ref 'VPC'

  ContainerSecurityGroupIngressFromSelf:
    Type: AWS::EC2::SecurityGroupIngress
    Properties:
      Description: Ingress from other memebers of the same SG
      GroupId: !Ref ContainerSecurityGroup
      IpProtocol: -1
      SourceSecurityGroupId: !Ref ContainerSecurityGroup

  # Autoscaling group. This launches the actual EC2 instances that will register
  # themselves as members of the cluster, and run the docker containers.
  ECSAutoScalingGroup:
    Type: AWS::AutoScaling::AutoScalingGroup
    Properties:
      VPCZoneIdentifier:
        - !Ref PrivateSubnetOne
        - !Ref PrivateSubnetTwo
      LaunchConfigurationName: !Ref 'ContainerInstances'
      MinSize: '1'
      MaxSize: !Ref 'MaxSize'
      DesiredCapacity: !Ref 'DesiredCapacity'
    CreationPolicy:
      ResourceSignal:
        Timeout: PT15M
    UpdatePolicy:
      AutoScalingReplacingUpdate:
        WillReplace: 'true'
  ContainerInstances:
    Type: AWS::AutoScaling::LaunchConfiguration
    Properties:
      ImageId: !Ref 'ECSAMI'
      SecurityGroups: [!Ref 'ContainerSecurityGroup']
      InstanceType: !Ref 'InstanceType'
      IamInstanceProfile: !Ref 'EC2InstanceProfile'
      UserData:
        Fn::Base64: !Sub |
          #!/bin/bash -xe
          echo ECS_CLUSTER=${ECSCluster} >> /etc/ecs/ecs.config
          yum install -y aws-cfn-bootstrap
          /opt/aws/bin/cfn-signal -e $? --stack ${AWS::StackName} --resource ECSAutoScalingGroup --region ${AWS::Region}
  EC2InstanceProfile:
    Type: AWS::IAM::InstanceProfile
    Properties:
      Path: /
      Roles: [!Ref 'EC2Role']

  # A role used to allow AWS Autoscaling to inspect stats and adjust scalable targets
  # on your AWS account
  AutoscalingRole:
    Type: AWS::IAM::Role
    Properties:
      AssumeRolePolicyDocument:
        Statement:
        - Effect: Allow
          Principal:
            Service: [application-autoscaling.amazonaws.com]
          Action: ['sts:AssumeRole']
      Path: /
      Policies:
      - PolicyName: service-autoscaling
        PolicyDocument:
          Statement:
          - Effect: Allow
            Action:
              - 'application-autoscaling:*'
              - 'cloudwatch:DescribeAlarms'
              - 'cloudwatch:PutMetricAlarm'
              - 'ecs:DescribeServices'
              - 'ecs:UpdateService'
            Resource: '*'

  # Role for the EC2 hosts. This allows the ECS agent on the EC2 hosts
  # to communicate with the ECS control plane, as well as download the docker
  # images from ECR to run on your host.
  EC2Role:
    Type: AWS::IAM::Role
    Properties:
      AssumeRolePolicyDocument:
        Statement:
        - Effect: Allow
          Principal:
            Service: [ec2.amazonaws.com]
          Action: ['sts:AssumeRole']
      Path: /
      Policies:
      - PolicyName: ecs-service
        PolicyDocument:
          Statement:
          - Effect: Allow
            Action:
              - 'ecs:CreateCluster'
              - 'ecs:DeregisterContainerInstance'
              - 'ecs:DiscoverPollEndpoint'
              - 'ecs:Poll'
              - 'ecs:RegisterContainerInstance'
              - 'ecs:StartTelemetrySession'
              - 'ecs:Submit*'
              - 'logs:CreateLogStream'
              - 'logs:PutLogEvents'
              - 'ecr:GetAuthorizationToken'
              - 'ecr:BatchGetImage'
              - 'ecr:GetDownloadUrlForLayer'
            Resource: '*'


# These are the values output by the CloudFormation template. Be careful
# about changing any of them, because of them are exported with specific
# names so that the other task related CF templates can use them.
Outputs:
  ClusterName:
    Description: The name of the ECS cluster
    Value: !Ref 'ECSCluster'
    Export:
      Name: !Sub ${EnvironmentName}:ClusterName
  AutoscalingRole:
    Description: The ARN of the role used for autoscaling
    Value: !GetAtt 'AutoscalingRole.Arn'
    Export:
      Name: !Sub ${EnvironmentName}:AutoscalingRole
  VpcId:
    Description: The ID of the VPC that this stack is deployed in
    Value: !Ref 'VPC'
    Export:
      Name: !Sub ${EnvironmentName}:VpcId
  PublicSubnetOne:
    Description: Public subnet one
    Value: !Ref 'PublicSubnetOne'
    Export:
      Name: !Sub ${EnvironmentName}:PublicSubnetOne
  PublicSubnetTwo:
    Description: Public subnet two
    Value: !Ref 'PublicSubnetTwo'
    Export:
      Name: !Sub ${EnvironmentName}:PublicSubnetTwo
  PrivateSubnetOne:
    Description: Private subnet one
    Value: !Ref 'PrivateSubnetOne'
    Export:
      Name: !Sub ${EnvironmentName}:PrivateSubnetOne
  PrivateSubnetTwo:
    Description: Private subnet two
    Value: !Ref 'PrivateSubnetTwo'
    Export:
      Name: !Sub ${EnvironmentName}:PrivateSubnetTwo
  ContainerSecurityGroup:
    Description: A security group used to allow containers to receive traffic
    Value: !Ref 'ContainerSecurityGroup'
    Export:
      Name: !Sub ${EnvironmentName}:ContainerSecurityGroup