ecs-cluster.yaml

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

  ECSAutoScalingGroup:
    Type: AWS::AutoScaling::AutoScalingGroup
    Properties: 
      VPCZoneIdentifier: !Ref Subnets
      LaunchConfigurationName: !Ref ECSLaunchConfiguration
      MinSize: !Ref MinSize
      MaxSize: !Ref MaxSize
      DesiredCapacity: !Ref ClusterSize
      Tags: 
        - Key: Name
          Value: !Sub ${EnvironmentName} ECS host
          PropagateAtLaunch: true
    CreationPolicy:
      ResourceSignal: 
        Timeout: PT15M
    UpdatePolicy:
      AutoScalingRollingUpdate:
        MinInstancesInService: !Ref RollingUpdateMinInstInService
        MaxBatchSize: !Ref RollingUpdateMaxBatchSize
        PauseTime: PT15M
        WaitOnResourceSignals: true
  
  ECSScaleUpPolicy:
    Type: AWS::AutoScaling::ScalingPolicy
    Properties:
      AdjustmentType: ChangeInCapacity
      AutoScalingGroupName: !Ref ECSAutoScalingGroup
      Cooldown: '180'
      ScalingAdjustment: '1'

  MemoryAlarmHigh:
    Type: AWS::CloudWatch::Alarm
    Properties:
      EvaluationPeriods: '1'
      Statistic: Sum
      Threshold: '70'
      AlarmDescription: Alarm if cluster is holding less memory than scaleable
      Period: '60'
      AlarmActions:
      - Ref: ECSScaleUpPolicy
      Namespace: AWS/ECS
      Dimensions:
      - Name: ClusterName
        Value:
          Ref: ECSCluster
      ComparisonOperator: GreaterThanThreshold
      MetricName: MemoryReservation