AWSTemplateFormatVersion: '2010-09-09'
Parameters:
  DMSReplicationInstanceName:
    Description: DMS Replication Instance name that you want to enable autoscaling
    Type: String
    Default: ""
  NotificationSNSTopic:
    Description: SNS Topic ARN that will be used for notifying autoscaling events
    Type: String
    Default: ""
  BucketName:
    Description: Name of the s3 bucket that holds configuration file
    Type: String
    Default: aws-database-blog
  S3KeyName:
    Description: Name of the configuration file
    Type: String
    Default: artifacts/auto_scale_DMS_replication_instance/instance_types.json
  Timeout:
    Description: Total timeout value after which lambda function notifies the user that replication instance modification timed out
    Type: String
    Default: artifacts/auto_scale_DMS_replication_instance/instance_types.json
Resources:
  iamRole:
    Type: AWS::IAM::Role
    Properties:
      AssumeRolePolicfyDocument:
        Version: '2012-10-17'
        Statement:
        - Effect: Allow
          Principal:
            Service:
            - lambda.amazonaws.com
          Action:
          - sts:AssumeRole
      Policies:
      - PolicyName: dmsautoscaler
        PolicyDocument:
          Version: '2012-10-17'
          Statement:
          - Sid: Stmt1528434137827
            Action:
            - s3:GetObject
            Effect: Allow
            Resource: "*"
          - Sid: Stmt1528434233173
            Action:
            - dms:DescribeReplicationInstances
            - dms:DescribeReplicationTasks
            - dms:ModifyReplicationInstance
            Effect: Allow
            Resource: "*"
          - Sid: Stmt1528473909949
            Action:
            - logs:CreateLogGroup
            - logs:CreateLogStream
            - logs:PutLogEvents
            Effect: Allow
            Resource: arn:aws:logs:*:*:*
          - Sid: Stmt1528473909943
            Action:
            - cloudwatch:DeleteAlarms
            - cloudwatch:EnableAlarmActions
            - cloudwatch:GetMetricData
            - cloudwatch:PutMetricAlarm
            Effect: Allow
            Resource: ["arn:aws:cloudwatch:::alarm:dms_cpu_high", "arn:aws:cloudwatch:::alarm:dms_cpu_low"]
          - Sid: Stmt1528473949712
            Action:
            - events:DeleteRule
            - events:EnableRule
            - events:PutRule
            - events:PutTargets
            - events:RemoveTargets
            Effect: Allow
            Resource: "arn:aws:events::107995894928:rule/dms-scheduled-event*"
          - Sid: Stmt1528474058666
            Action:
            - lambda:AddPermission
            - lambda:RemovePermission
            Effect: Allow
            Resource: arn:aws:lambda:*:*:function:dms_autoscaler_cf
          - Sid: Stmt1528474139639
            Action:
            - sns:Publish
            Effect: Allow
            Resource: "*"
      RoleName: dmsautoscalerrole
  lambdaFunction:
    Type: AWS::Lambda::Function
    Properties:
      Code:
        S3Bucket: aws-database-blog
        S3Key: artifacts/auto_scale_DMS_replication_instance/dms.py.zip
      FunctionName: dms_autoscaler_cf
      Handler: dms.lambda_handler
      Environment:
        Variables:
          TOPIC_ARN:
            Ref: NotificationSNSTopic
          BUCKET_NAME:
            Ref: BucketName
          KEY_NAME:
            Ref: S3KeyName
          MODFICATION_TIMEOUT:
            Ref: Timeout
      Runtime: python3.7
      MemorySize: 128
      Timeout: 30
      Description: DMS Autoscaler
      Role:
        Fn::GetAtt:
        - iamRole
        - Arn
  lambdaPermission:
    Type: AWS::Lambda::Permission
    Properties:
      Action: lambda:InvokeFunction
      FunctionName: dms_autoscaler_cf
      Principal: sns.amazonaws.com
      SourceArn:
        Ref: snsTopic
  snsTopic:
    Type: AWS::SNS::Topic
    Properties:
      DisplayName: dmsautoscaler_cf
      Subscription:
      - Endpoint:
          Fn::GetAtt:
          - lambdaFunction
          - Arn
        Protocol: lambda
      TopicName: dmsautoscaler_cf
  cloudWatchHighCPUAlarm:
    Type: AWS::CloudWatch::Alarm
    Properties:
      MetricName: CPUUtilization
      Namespace: AWS/DMS
      ComparisonOperator: GreaterThanOrEqualToThreshold
      EvaluationPeriods: '1'
      Period: '60'
      Statistic: Average
      Threshold: '80'
      ActionsEnabled: 'true'
      AlarmActions:
      - Ref: snsTopic
      Dimensions:
      - Name: ReplicationInstanceIdentifier
        Value:
          Ref: DMSReplicationInstanceName
      AlarmDescription: High CPU usage by DMS instance.
      AlarmName: dms_cpu_high
  cloudWatchLowCPUAlarm:
    Type: AWS::CloudWatch::Alarm
    Properties:
      MetricName: CPUUtilization
      Namespace: AWS/DMS
      ComparisonOperator: LessThanOrEqualToThreshold
      EvaluationPeriods: '1'
      Period: '60'
      Statistic: Average
      Threshold: '30'
      ActionsEnabled: 'true'
      AlarmActions:
      - Ref: snsTopic
      Dimensions:
      - Name: ReplicationInstanceIdentifier
        Value:
          Ref: DMSReplicationInstanceName
      AlarmDescription: Low CPU usage by DMS instance.
      AlarmName: dms_cpu_low
Outputs:
  IAMRole:
    Description: IAM Role for the lambda function
    Value:
      Fn::GetAtt:
      - iamRole
      - Arn
  LambdaFunction:
    Description: DMS Autoscaler lambda function
    Value:
      Fn::GetAtt:
      - lambdaFunction
      - Arn
  SNSTopic:
    Description: SNS Topic that will act as bridge between cloudwatch alarm and lambda
      function
    Value:
      Ref: snsTopic