AWSTemplateFormatVersion: '2010-09-09'
Description: 'Bottlerocket ECS updater automation & resources'
Parameters:
  ClusterName:
    Description: 'Name of ECS cluster to manage Bottlerocket instances in'
    Type: String
  Subnets:
    Description: 'List of VPC Subnet IDs where the updater should run. The subnets must have a route to the Internet via an Internet Gateway.'
    Type: List<AWS::EC2::Subnet::Id>
  UpdaterImage:
    Description: 'Bottlerocket updater container image'
    Type: String
    Default: 'public.ecr.aws/bottlerocket/bottlerocket-ecs-updater:v0.2.2'
  LogGroupName:
    Description: 'Log group name for Bottlerocket updater logs'
    Type: String
  ScheduleState:
    Description: 'Schedule events rule state; allows disabling of scheduling'
    Type: String
    Default: 'ENABLED'
Resources:
  ExecutionRole:
    Type: 'AWS::IAM::Role'
    Properties:
      AssumeRolePolicyDocument:
        Version: '2012-10-17'
        Statement:
          - Effect: Allow
            Principal:
              Service:
                - 'ecs-tasks.amazonaws.com'
            Action:
              - 'sts:AssumeRole'
      Policies:
        - PolicyName: CreateLogGroupPolicy
          PolicyDocument:
            Version: '2012-10-17'
            Statement:
              # Allows creating log group if it does not exist
              - Effect: Allow
                Action:
                  - 'logs:CreateLogGroup'
                Resource:
                  - 'arn:aws:logs:*:*:*'
      Path: !Sub /${AWS::StackName}/
      ManagedPolicyArns:
        - !Sub 'arn:${AWS::Partition}:iam::aws:policy/service-role/AmazonECSTaskExecutionRolePolicy'
  TaskRole:
    Type: AWS::IAM::Role
    Properties:
      Description: 'Role allowing the Bottlerocket ECS Updater to manage Bottlerocket instances'
      Path: !Sub '/${AWS::StackName}/'
      AssumeRolePolicyDocument:
        Version: 2012-10-17
        Statement:
          - Effect: Allow
            Principal:
              Service: 'ecs-tasks.amazonaws.com'
            Action:
              - 'sts:AssumeRole'
      Policies:
        - PolicyName: 'BottlerocketEcsUpdaterPolicy'
          PolicyDocument:
            Version: 2012-10-17
            Statement:
              # Allows listing all container instances in a cluster
              - Effect: Allow
                Action:
                  - 'ecs:ListContainerInstances'
                Resource:
                  - !Sub 'arn:${AWS::Partition}:ecs:${AWS::Region}:${AWS::AccountId}:cluster/${ClusterName}'
              # Allows describe container instances to get ec2 instance ID and ecs attributes to filter Bottlerocket instances
              # Allows list tasks to filter instances running standalone tasks
              # Allows update container instance state for draining
              # Allows describe tasks to identify tasks not started by service
              - Effect: Allow
                Action:
                  - 'ecs:DescribeContainerInstances'
                  - 'ecs:ListTasks'
                  - 'ecs:UpdateContainerInstancesState'
                  - 'ecs:DescribeTasks'
                Resource: '*'
                Condition:
                  ArnEquals:
                    ecs:cluster: !Sub 'arn:${AWS::Partition}:ecs:${AWS::Region}:${AWS::AccountId}:cluster/${ClusterName}'
              # Allows ssm send command to make Bottlerocket update API calls
              - Effect: Allow
                Action:
                  - 'ssm:SendCommand'
                Resource:
                  - !Sub "arn:${AWS::Partition}:ssm:${AWS::Region}:${AWS::AccountId}:document/${UpdateCheckCommand}"
                  - !Sub "arn:${AWS::Partition}:ssm:${AWS::Region}:${AWS::AccountId}:document/${UpdateApplyCommand}"
                  - !Sub "arn:${AWS::Partition}:ssm:${AWS::Region}:${AWS::AccountId}:document/${RebootCommand}"
                  - !Sub "arn:${AWS::Partition}:ec2:${AWS::Region}:${AWS::AccountId}:instance/*"
              # Allows get command invocation to get Bottlerocket API calls output
              - Effect: Allow
                Action:
                  - 'ssm:GetCommandInvocation'
                Resource:
                  - !Sub "arn:${AWS::Partition}:ssm:${AWS::Region}:${AWS::AccountId}:*"
              # Allows checking the EC2 instance state after an update occurs
              - Effect: Allow
                Action:
                  - 'ec2:DescribeInstanceStatus'
                Resource: '*'
  UpdaterTaskDefinition:
    Type: AWS::ECS::TaskDefinition
    Properties:
      NetworkMode: awsvpc
      RequiresCompatibilities:
        - FARGATE
      Cpu: "256"
      Memory: "0.5GB"
      ExecutionRoleArn: !GetAtt ExecutionRole.Arn
      TaskRoleArn: !GetAtt TaskRole.Arn
      ContainerDefinitions:
        - Name: BottlerocketEcsUpdaterService
          Image: !Ref UpdaterImage
          Command:
            - -cluster
            - !Ref ClusterName
            - -region
            - !Ref AWS::Region
            - -check-document
            - !Ref UpdateCheckCommand
            - -apply-document
            - !Ref UpdateApplyCommand
            - -reboot-document
            - !Ref RebootCommand
          LogConfiguration:
            LogDriver: awslogs
            Options:
              awslogs-create-group: 'true'
              awslogs-region: !Ref AWS::Region
              awslogs-group: !Ref LogGroupName
              awslogs-stream-prefix: !Sub '/ecs/bottlerocket-updater/${ClusterName}'
  BottlerocketUpdaterSchedule:
    Type: AWS::Events::Rule
    Properties:
      Description: "Check for Bottlerocket updates on a schedule"
      # Run Task every 12 hours
      ScheduleExpression: "rate(12 hours)"
      State: !Ref ScheduleState
      Targets:
        - Id: ecs-updater-fargate-task
          RoleArn: !GetAtt CronRole.Arn
          Arn: !Sub 'arn:${AWS::Partition}:ecs:${AWS::Region}:${AWS::AccountId}:cluster/${ClusterName}'
          Input:
             !Sub |
              {
                  "containerOverrides": [
                      {
                         "name": "BottlerocketEcsUpdaterService",
                         "environment": [
                             {
                                 "name" : "TASK_DEFINITION_ARN",
                                 "value": "${UpdaterTaskDefinition}"
                             }
                         ]
                      }
                  ]
              }
          EcsParameters:
            LaunchType: FARGATE
            TaskCount: 1
            TaskDefinitionArn: !Ref UpdaterTaskDefinition
            NetworkConfiguration:
              AwsVpcConfiguration:
                # The Bottlerocket ECS Updater does not need a public IP for its operations. The public IP
                # is only required to pull images from ECR as a Fargate task
                AssignPublicIp: ENABLED
                Subnets: !Ref Subnets
  CronRole:
    Type: AWS::IAM::Role
    Properties:
      AssumeRolePolicyDocument:
        Version: "2012-10-17"
        Statement:
          - Effect: "Allow"
            Principal:
              Service:
                - "events.amazonaws.com"
            Action:
              - "sts:AssumeRole"
      Path: !Sub '/${AWS::StackName}/'
      Policies:
        - PolicyName: "BottlerocketEcsUpdaterSchedulerPolicy"
          PolicyDocument:
            Statement:
              - Effect: "Allow"
                Condition:
                  ArnEquals:
                    ecs:cluster: !Sub 'arn:${AWS::Partition}:ecs:${AWS::Region}:${AWS::AccountId}:cluster/${ClusterName}'
                Action: "ecs:RunTask"
                Resource:
                  - !Ref UpdaterTaskDefinition
              - Effect: "Allow"
                Condition:
                  ArnEquals:
                    ecs:cluster: !Sub 'arn:${AWS::Partition}:ecs:${AWS::Region}:${AWS::AccountId}:cluster/${ClusterName}'
                Action:
                  - "iam:PassRole"
                Resource:
                  - !GetAtt TaskRole.Arn
                  - !GetAtt ExecutionRole.Arn
  UpdateCheckCommand:
    Type: AWS::SSM::Document
    Properties:
      DocumentType: Command
      Content:
        schemaVersion: "2.2"
        description: "Bottlerocket - Check available updates"
        mainSteps:
          - action: "aws:runShellScript"
            name: "CheckUpdate"
            precondition:
              StringEquals:
                - platformType
                - Linux
            inputs:
              timeoutSeconds: '1800'
              runCommand:
                - "apiclient update check"
  UpdateApplyCommand:
    Type: AWS::SSM::Document
    Properties:
      DocumentType: Command
      Content:
        schemaVersion: "2.2"
        description: "Bottlerocket - Apply update"
        mainSteps:
          - action: "aws:runShellScript"
            name: "ApplyUpdate"
            precondition:
              StringEquals:
                - platformType
                - Linux
            inputs:
              timeoutSeconds: '1800'
              runCommand:
                - "apiclient update apply"
  RebootCommand:
    Type: AWS::SSM::Document
    Properties:
      DocumentType: Command
      Content:
        schemaVersion: "2.2"
        description: "Bottlerocket - Reboot"
        mainSteps:
          - action: "aws:runShellScript"
            name: "Reboot"
            precondition:
              StringEquals:
                - platformType
                - Linux
            inputs:
              timeoutSeconds: '1800'
              runCommand:
                - "apiclient reboot"
Outputs:
  UpdaterTaskDefinitionArn:
    Description: 'Updater task definition ARN'
    Value: !Ref UpdaterTaskDefinition
    Export:
      Name: !Sub "${AWS::StackName}:UpdaterTaskDefinition"