NGINX reverse proxy sidecar for a web container hosted with Amazon ECS and AWS Fargate

AWSTemplateFormatVersion: '2010-09-09'
Description: Empty ECS cluster that has no EC2 instances. It is designed
             to be used with AWS Fargate serverless capacity

Resources:
  # Cluster that keeps track of container deployments
  ECSCluster:
    Type: AWS::ECS::Cluster
    Properties:
      ClusterSettings:
        - Name: containerInsights
          Value: enabled

  # This is a role which is used within Fargate to allow the Fargate agent
  # to download images, and upload logs.
  ECSTaskExecutionRole:
    Type: AWS::IAM::Role
    Properties:
      AssumeRolePolicyDocument:
        Statement:
          - Effect: Allow
            Principal:
              Service: [ecs-tasks.amazonaws.com]
            Action: ['sts:AssumeRole']
            Condition:
              ArnLike:
                aws:SourceArn: !Sub arn:aws:ecs:${AWS::Region}:${AWS::AccountId}:*
              StringEquals:
                aws:SourceAccount: !Ref AWS::AccountId
      Path: /

      # This role enables basic features of ECS. See reference:
      # https://docs.aws.amazon.com/AmazonECS/latest/developerguide/security-iam-awsmanpol.html#security-iam-awsmanpol-AmazonECSTaskExecutionRolePolicy
      ManagedPolicyArns:
        - arn:aws:iam::aws:policy/service-role/AmazonECSTaskExecutionRolePolicy

Outputs:
  ClusterName:
    Description: The ECS cluster into which to launch resources
    Value: !Ref ECSCluster
  ECSTaskExecutionRole:
    Description: The role used to start up a task
    Value: !Ref ECSTaskExecutionRole

AWSTemplateFormatVersion: '2010-09-09'
Description: An example service that deploys in AWS VPC networking mode
             on AWS Fargate. Service runs with networking in public
             subnets and public IP addresses

Parameters:
  VpcId:
    Type: String
    Description: The VPC that the service is running inside of
  PublicSubnetIds:
    Type: List<AWS::EC2::Subnet::Id>
    Description: List of public subnet ID's to put the load balancer and tasks in
  ClusterName:
    Type: String
    Description: The name of the ECS cluster into which to launch capacity.
  ECSTaskExecutionRole:
    Type: String
    Description: The role used to start up an ECS task
  ServiceName:
    Type: String
    Default: web
    Description: A name for the service
  AppImageUrl:
    Type: String
    Description: The url of a docker image that contains the application process that
                 will handle the traffic for this service
  NginxImageUrl:
    Type: String
    Description: The url of a docker image that provides the NGINX reverse proxy
  ContainerCpu:
    Type: Number
    Default: 1024
    Description: How much CPU to give the container. 1024 is 1 CPU
  ContainerMemory:
    Type: Number
    Default: 2048
    Description: How much memory in megabytes to give the container
  ContainerPort:
    Type: Number
    Default: 80
    Description: What port that the application expects traffic on
  DesiredCount:
    Type: Number
    Default: 2
    Description: How many copies of the service task to run

Resources:

  # The task definition. This is a simple metadata description of what
  # container(s) to run, and what resource requirements the task has
  TaskDefinition:
    Type: AWS::ECS::TaskDefinition
    Properties:
      Family: !Ref ServiceName
      Cpu: !Ref ContainerCpu
      Memory: !Ref ContainerMemory
      NetworkMode: awsvpc
      RequiresCompatibilities:
        - FARGATE
      ExecutionRoleArn: !Ref ECSTaskExecutionRole
      ContainerDefinitions:
        # NGINX sidecar for the task
        - Name: nginx
          Image: !Ref NginxImageUrl
          PortMappings:
            - ContainerPort: !Ref ContainerPort
              HostPort: !Ref ContainerPort
          LogConfiguration:
            LogDriver: 'awslogs'
            Options:
              mode: non-blocking
              max-buffer-size: 25m
              awslogs-group: !Ref NginxLogGroup
              awslogs-region: !Ref AWS::Region
              awslogs-stream-prefix: !Sub "${ServiceName}/nginx"
        # Application container
        - Name: app
          Image: !Ref AppImageUrl
          LogConfiguration:
            LogDriver: 'awslogs'
            Options:
              mode: non-blocking
              max-buffer-size: 25m
              awslogs-group: !Ref AppLogGroup
              awslogs-region: !Ref AWS::Region
              awslogs-stream-prefix: !Sub "${ServiceName}/app"

  # The service. The service is a resource which allows you to run multiple
  # copies of a type of task, and gather up their logs and metrics, as well
  # as monitor the number of running tasks and replace any that have crashed
  Service:
    Type: AWS::ECS::Service
    # Avoid race condition between ECS service creation and associating
    # the target group with the LB
    DependsOn: PublicLoadBalancerListener
    Properties:
      ServiceName: !Ref ServiceName
      Cluster: !Ref ClusterName
      LaunchType: FARGATE
      NetworkConfiguration:
        AwsvpcConfiguration:
          AssignPublicIp: ENABLED
          SecurityGroups:
            - !Ref ServiceSecurityGroup
          Subnets: !Ref PublicSubnetIds
      DeploymentConfiguration:
        MaximumPercent: 200
        MinimumHealthyPercent: 75
      DesiredCount: !Ref DesiredCount
      TaskDefinition: !Ref TaskDefinition
      LoadBalancers:
        - ContainerName: nginx
          ContainerPort: !Ref ContainerPort
          TargetGroupArn: !Ref ServiceTargetGroup

  # Security group that limits network access
  # to the task
  ServiceSecurityGroup:
    Type: AWS::EC2::SecurityGroup
    Properties:
      GroupDescription: Security group for service
      VpcId: !Ref VpcId

  # Keeps track of the list of tasks for the service
  ServiceTargetGroup:
    Type: AWS::ElasticLoadBalancingV2::TargetGroup
    Properties:
      HealthCheckIntervalSeconds: 6
      HealthCheckPath: /
      HealthCheckProtocol: HTTP
      HealthCheckTimeoutSeconds: 5
      HealthyThresholdCount: 2
      TargetType: ip
      Port: !Ref ContainerPort
      Protocol: HTTP
      UnhealthyThresholdCount: 10
      VpcId: !Ref VpcId
      TargetGroupAttributes:
        - Key: deregistration_delay.timeout_seconds
          Value: 0

  # A public facing load balancer, this is used as ingress for
  # public facing internet traffic.
  PublicLoadBalancerSG:
    Type: AWS::EC2::SecurityGroup
    Properties:
      GroupDescription: Access to the public facing load balancer
      VpcId: !Ref VpcId
      SecurityGroupIngress:
        # Allow access to public facing ALB from any IP address
        - CidrIp: 0.0.0.0/0
          IpProtocol: -1
  PublicLoadBalancer:
    Type: AWS::ElasticLoadBalancingV2::LoadBalancer
    Properties:
      Scheme: internet-facing
      LoadBalancerAttributes:
      - Key: idle_timeout.timeout_seconds
        Value: '30'
      Subnets: !Ref PublicSubnetIds
      SecurityGroups:
        - !Ref PublicLoadBalancerSG
  PublicLoadBalancerListener:
    Type: AWS::ElasticLoadBalancingV2::Listener
    Properties:
      DefaultActions:
        - Type: 'forward'
          ForwardConfig:
            TargetGroups:
              - TargetGroupArn: !Ref ServiceTargetGroup
                Weight: 100
      LoadBalancerArn: !Ref 'PublicLoadBalancer'
      Port: 80
      Protocol: HTTP

  # Open up the service's security group to traffic originating
  # from the security group of the load balancer.
  ServiceIngressfromLoadBalancer:
    Type: AWS::EC2::SecurityGroupIngress
    Properties:
      Description: Ingress from the public ALB
      GroupId: !Ref ServiceSecurityGroup
      IpProtocol: -1
      SourceSecurityGroupId: !Ref 'PublicLoadBalancerSG'

  # This log group stores the stdout logs from the app
  AppLogGroup:
    Type: AWS::Logs::LogGroup

  # This log group stores the access logs from NGINX
  NginxLogGroup:
    Type: AWS::Logs::LogGroup

AWSTemplateFormatVersion: "2010-09-09"
Transform: AWS::Serverless-2016-10-31
Description: Parent stack that deploys a serverless AWS Fargate web service.
             The service tasks use an NGINX reverse proxy in front of the application.
Parameters:
  AppImageUrl:
    Type: String
    Description: The url of a docker image that contains the application process that
                 will handle the traffic for this service
  NginxImageUrl:
    Type: String
    Description: The url of a docker image that provides the NGINX reverse proxy

Resources:

  # The networking configuration. This creates an isolated
  # network specific to this particular environment
  VpcStack:
    Type: AWS::Serverless::Application
    Properties:
      Location: vpc.yml

  # This stack contains the Amazon ECS cluster itself
  ClusterStack:
    Type: AWS::Serverless::Application
    Properties:
      Location: cluster.yml

  # This stack contains the container deployment
  ServiceStack:
    Type: AWS::Serverless::Application
    Properties:
      Location: service.yml
      Parameters:
        VpcId: !GetAtt VpcStack.Outputs.VpcId
        PublicSubnetIds: !GetAtt VpcStack.Outputs.PublicSubnetIds
        ClusterName: !GetAtt ClusterStack.Outputs.ClusterName
        ECSTaskExecutionRole: !GetAtt ClusterStack.Outputs.ECSTaskExecutionRole
        AppImageUrl: !Ref AppImageUrl
        NginxImageUrl: !Ref NginxImageUrl