#source: https://github.com/awslabs/aws-cloudformation-templates/tree/master/aws/services/ECS
AWSTemplateFormatVersion: '2010-09-09'
Description: This stack deploys a Fargate cluster that is in a VPC with both
             public and private subnets. Containers can be deployed into either
             the public subnets or the private subnets, and there are two load
             balancers. One is inside the public subnet, which can be used to
             send traffic to the containers in the private subnet, and one in
             the private subnet, which can be used for private internal traffic
             between internal services. (fdp-1qj64b304)
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: '10.0.2.0/24'
    PrivateTwo:
      CIDR: '10.0.3.0/24'
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: "FargateClusterVPC"

  # VPC flow logs that that enables you to capture information about
  # the IP traffic going to and from network interfaces in your VPC
  VPCFlowLogs:
    Type: AWS::EC2::FlowLog
    Properties: 
      DeliverLogsPermissionArn: !GetAtt FlowLogsRole.Arn
      LogGroupName: !Ref FlowLogGroup
      ResourceId: !Ref VPC
      ResourceType: VPC
      TrafficType: ALL

  # VPC flow logs can publish data to CloudWatch logs
  FlowLogGroup:
      Type: AWS::Logs::LogGroup
      Properties:
        RetentionInDays: '30'
  # Two public subnets, where containers can have public IP addresses
  PublicSubnetOne:
    Type: AWS::EC2::Subnet
    Properties:
      AvailabilityZone:
         Fn::Select:
         - 0
         - Fn::GetAZs: {Ref: 'AWS::Region'}
      VpcId: !Ref 'VPC'
      CidrBlock: !FindInMap ['SubnetConfig', 'PublicOne', 'CIDR']
      MapPublicIpOnLaunch: true
      Tags:
        - 
          Key: "Name"
          Value: "PublicSubnetOne"
  PublicSubnetTwo:
    Type: AWS::EC2::Subnet
    Properties:
      AvailabilityZone:
         Fn::Select:
         - 1
         - Fn::GetAZs: {Ref: 'AWS::Region'}
      VpcId: !Ref 'VPC'
      CidrBlock: !FindInMap ['SubnetConfig', 'PublicTwo', 'CIDR']
      MapPublicIpOnLaunch: true
      Tags:
        - 
          Key: "Name"
          Value: "PublicSubnetTwo"

  # 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:
         Fn::Select:
         - 0
         - Fn::GetAZs: {Ref: 'AWS::Region'}
      VpcId: !Ref 'VPC'
      CidrBlock: !FindInMap ['SubnetConfig', 'PrivateOne', 'CIDR']
      Tags:
        - 
          Key: "Name"
          Value: "PrivateSubnetOne"
  PrivateSubnetTwo:
    Type: AWS::EC2::Subnet
    Properties:
      AvailabilityZone:
         Fn::Select:
         - 1
         - Fn::GetAZs: {Ref: 'AWS::Region'}
      VpcId: !Ref 'VPC'
      CidrBlock: !FindInMap ['SubnetConfig', 'PrivateTwo', 'CIDR']
      Tags:
        - 
          Key: "Name"
          Value: "PrivateSubnetTwo"

  # 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
  GatewayAttachement:
    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: GatewayAttachement
    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: GatewayAttachement
    Properties:
        Domain: vpc
  NatGatewayTwoAttachment:
    Type: AWS::EC2::EIP
    DependsOn: GatewayAttachement
    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

  # OPTIONAL: VPC Endpoint for DynamoDB
  # If a container needs to access DynamoDB this allows a container in the private subnet
  # to talk to DynamoDB directly without needing to go via the NAT gateway. This reduces
  # the amount of bandwidth through the gateway, meaning that the gateway is free to serve
  # your other traffic.
  DynamoDBEndpoint:
    Type: AWS::EC2::VPCEndpoint
    Properties:
      PolicyDocument:
        Version: "2012-10-17"
        Statement:
          - Effect: Allow
            Action: "*"
            Principal: "*"
            Resource: "*"
      RouteTableIds:
        - !Ref 'PrivateRouteTableOne'
        - !Ref 'PrivateRouteTableTwo'
      ServiceName: !Join [ "", [ "com.amazonaws.", { "Ref": "AWS::Region" }, ".dynamodb" ] ]
      VpcId: !Ref 'VPC'

  # ECS Resources
  ECSCluster:
    Type: AWS::ECS::Cluster

  # A security group for the containers we will run in Fargate.
  # Three rules, allowing network traffic from a public facing load
  # balancer, a private internal load balancer, and from other members
  # of the security group.
  #
  # Remove any of the following ingress rules that are not needed.
  FargateContainerSecurityGroup:
    Type: AWS::EC2::SecurityGroup
    Properties:
      GroupDescription: Fargate container security group. Use this for all tasks and services.
      VpcId: !Ref 'VPC'
      Tags:
        - 
          Key: "Name"
          Value: "FargateContainerSecurityGroup"
      
  EcsSecurityGroupIngressFromPublicALB:
    Type: AWS::EC2::SecurityGroupIngress
    Properties:
      Description: Ingress from the public ALB
      GroupId: !Ref 'FargateContainerSecurityGroup'
      IpProtocol: -1
      SourceSecurityGroupId: !Ref 'PublicLoadBalancerSG'
  EcsSecurityGroupIngressFromPrivateALB:
    Type: AWS::EC2::SecurityGroupIngress
    Properties:
      Description: Ingress from the private ALB
      GroupId: !Ref 'FargateContainerSecurityGroup'
      IpProtocol: -1
      SourceSecurityGroupId: !Ref 'PrivateLoadBalancerSG'
  EcsSecurityGroupIngressFromSelf:
    Type: AWS::EC2::SecurityGroupIngress
    Properties:
      Description: Ingress from other containers in the same security group
      GroupId: !Ref 'FargateContainerSecurityGroup'
      IpProtocol: -1
      SourceSecurityGroupId: !Ref 'FargateContainerSecurityGroup'

  # Load balancers for getting traffic to containers.
  # This sample template creates two load balancers:
  #
  # - One public load balancer, hosted in public subnets that is accessible
  #   to the public, and is intended to route traffic to one or more public
  #   facing services.
  # - One private load balancer, hosted in private subnets, that only
  #   accepts traffic from other containers in the Fargate cluster, and is
  #   intended for private services that should not be accessed directly
  #   by the public.

  # A public facing load balancer, this is used for accepting traffic from the public
  # internet and directing it to public facing microservices
  PublicLoadBalancerSG:
    Type: AWS::EC2::SecurityGroup
    Properties:
      GroupDescription: Public facing load balancer Security Group
      VpcId: !Ref 'VPC'
      SecurityGroupIngress:
          # Allow access to ALB from anywhere on the internet
          - CidrIp: 0.0.0.0/0
            IpProtocol: -1
  PublicLoadBalancer:
    Type: AWS::ElasticLoadBalancingV2::LoadBalancer
    DependsOn: GatewayAttachement
    Properties:
      Scheme: internet-facing
      LoadBalancerAttributes:
      - Key: idle_timeout.timeout_seconds
        Value: '30'
      Subnets:
        # The load balancer is placed into the public subnets, so that traffic
        # from the internet can reach the load balancer directly via the internet gateway
        - !Ref PublicSubnetOne
        - !Ref PublicSubnetTwo
      SecurityGroups: [!Ref 'PublicLoadBalancerSG']
  

  # An internal load balancer, this would be used for a service that is not
  # directly accessible to the public, but instead should only receive traffic
  # from your other services.
  PrivateLoadBalancerSG:
    Type: AWS::EC2::SecurityGroup
    Properties:
      GroupDescription: Internal load balancer security group
      VpcId: !Ref 'VPC'
  PrivateLoadBalancerIngressFromECS:
    Type: AWS::EC2::SecurityGroupIngress
    Properties:
      Description: Only accept traffic from a container in the fargate container security group
      GroupId: !Ref 'PrivateLoadBalancerSG'
      IpProtocol: -1
      SourceSecurityGroupId: !Ref 'FargateContainerSecurityGroup'
  PrivateLoadBalancer:
    Type: AWS::ElasticLoadBalancingV2::LoadBalancer
    Properties:
      Scheme: internal
      LoadBalancerAttributes:
      - Key: idle_timeout.timeout_seconds
        Value: '30'
      Subnets:
        # This load balancer is put into the private subnet, so that there is no
        # route for the public to even be able to access the private load balancer.
        - !Ref PrivateSubnetOne
        - !Ref PrivateSubnetTwo
      SecurityGroups: [!Ref 'PrivateLoadBalancerSG']
  

  # This is an IAM role which authorizes ECS to manage resources on your
  # account on your behalf, such as updating your load balancer with the
  # details of where your containers are, so that traffic can reach your
  # containers.
  ECSRole:
    Type: AWS::IAM::Role
    Properties:
      AssumeRolePolicyDocument:
        Statement:
        - Effect: Allow
          Principal:
            Service: [ecs.amazonaws.com]
          Action: ['sts:AssumeRole']
      Path: /
      Policies:
      - PolicyName: ecs-service
        PolicyDocument:
          Statement:
          - Effect: Allow
            Action:
              # Rules which allow ECS to attach network interfaces to instances
              # on your behalf in order for awsvpc networking mode to work right
              - 'ec2:AttachNetworkInterface'
              - 'ec2:CreateNetworkInterface'
              - 'ec2:CreateNetworkInterfacePermission'
              - 'ec2:DeleteNetworkInterface'
              - 'ec2:DeleteNetworkInterfacePermission'
              - 'ec2:Describe*'
              - 'ec2:DetachNetworkInterface'

              # Rules which allow ECS to update load balancers on your behalf
              # with the information sabout how to send traffic to your containers
              - 'elasticloadbalancing:DeregisterInstancesFromLoadBalancer'
              - 'elasticloadbalancing:DeregisterTargets'
              - 'elasticloadbalancing:Describe*'
              - 'elasticloadbalancing:RegisterInstancesWithLoadBalancer'
              - 'elasticloadbalancing:RegisterTargets'
            Resource: '*'

  # This is a role which is used by the ECS tasks themselves.
  ECSTaskExecutionRole:
    Type: AWS::IAM::Role
    Properties:
      AssumeRolePolicyDocument:
        Statement:
        - Effect: Allow
          Principal:
            Service: [ecs-tasks.amazonaws.com]
          Action: ['sts:AssumeRole']
      Path: /
      Policies:
        - PolicyName: AmazonECSTaskExecutionRolePolicy
          PolicyDocument:
            Statement:
            - Effect: Allow
              Action:
                # Allow the ECS Tasks to download images from ECR
                - 'ecr:GetAuthorizationToken'
                - 'ecr:BatchCheckLayerAvailability'
                - 'ecr:GetDownloadUrlForLayer'
                - 'ecr:BatchGetImage'

                # Allow the ECS tasks to upload logs to CloudWatch
                - 'logs:CreateLogStream'
                - 'logs:PutLogEvents'
                - 'logs:CreateLogGroup'
                - 'logs:DescribeLogStreams'                
              Resource: '*'

  # This is a role which is used to publish flow logs to the specified log group in CloudWatch Logs
  FlowLogsRole:
    Type: 'AWS::IAM::Role'
    Properties:
      AssumeRolePolicyDocument:
        Version: '2012-10-17'
        Statement:
        - Effect: Allow
          Principal:
            Service: 'vpc-flow-logs.amazonaws.com'
          Action: 'sts:AssumeRole'
      Policies:
      - PolicyName: 'flowlogs-policy'
        PolicyDocument:
          Version: '2012-10-17'
          Statement:
          - Effect: Allow
            Action:
            - 'logs:CreateLogStream'
            - 'logs:PutLogEvents'
            - 'logs:DescribeLogGroups'
            - 'logs:DescribeLogStreams'
            Resource: !GetAtt FlowLogGroup.Arn

# 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: 'FargateClusterName'
  InternalUrl:
    Description: The url of the internal load balancer
    Value: !Join ['', ['http://', !GetAtt 'PrivateLoadBalancer.DNSName']]
    Export:
      Name: !Join [ ':', [ !Ref 'AWS::StackName', 'InternalUrl' ] ]
  ExternalUrl:
    Description: The url of the external load balancer
    Value: !Join ['', ['http://', !GetAtt 'PublicLoadBalancer.DNSName']]
    Export:
      Name: !Join [ ':', [ !Ref 'AWS::StackName', 'ExternalUrl' ] ]
  ECSPublicLoadBalancer:
    Description: The ARN of the Public LoadBalancer
    Value: !Ref 'PublicLoadBalancer'
    Export:
      Name: 'ECSPublicLoadBalancer'
  ECSTaskExecutionRole:
    Description: The ARN of the ECS role
    Value: !GetAtt 'ECSTaskExecutionRole.Arn'
    Export:
      Name: 'ECSTaskExecutionRole'
  VPCId:
    Description: The ID of the VPC that this stack is deployed in
    Value: !Ref 'VPC'
    Export:
      Name: 'FargateClusterVPCId'
  PublicSubnetOne:
    Description: Public subnet one
    Value: !Ref 'PublicSubnetOne'
    Export:
      Name: !Join [ ':', [ !Ref 'AWS::StackName', 'PublicSubnetOne' ] ]
  PublicSubnetTwo:
    Description: Public subnet two
    Value: !Ref 'PublicSubnetTwo'
    Export:
      Name: !Join [ ':', [ !Ref 'AWS::StackName', 'PublicSubnetTwo' ] ]
  PrivateSubnetOne:
    Description: Private subnet one
    Value: !Ref 'PrivateSubnetOne'
    Export:
      Name: 'ECSPrivateSubnetOne'
  PrivateSubnetTwo:
    Description: Private subnet two
    Value: !Ref 'PrivateSubnetTwo'
    Export:
      Name: 'ECSPrivateSubnetTwo'
  FargateContainerSecurityGroup:
    Description: A security group for Fargate containers, tasks, and services
    Value: !Ref 'FargateContainerSecurityGroup'
    Export:
      Name: 'ECSFargateContainerSecurityGroup'