AWS::CloudWatch::Alarm.Period >= 60 for metrics in the AWS/ namespace

[irvingpop]

cfn-lint version: (cfn-lint --version)

cfn-lint 0.22.3

Description of issue.

AWS won't let you set AWS::CloudWatch::Alarm.Period less than 60, it would be neat if cfn-lint flagged that.

Please provide as much information as possible:

The following resource should get flagged because the Period property is invalid, but doesn't:

  ELB5XXExceeded:
    Type: AWS::CloudWatch::Alarm
    Properties:
      AlarmName: !Sub AppELB_5XX_Exceeded-${AWS::StackName}
      AlarmDescription: Alarms when an 5xx requests exceed a specified threshold.
      AlarmActions: [!Ref AlertNotificationTopic]
      MetricName: HTTPCode_ELB_5XX_Count
      Namespace: AWS/ApplicationELB
      ComparisonOperator: GreaterThanOrEqualToThreshold
      EvaluationPeriods: 2
      Period: 30
      Statistic: Sum
      Threshold: 10
      Dimensions:
        - Name: LoadBalancer
          Value: !GetAtt ChefALB.LoadBalancerFullName

Cfn-lint uses the CloudFormation Resource Specifications as the base to do validation. These files are included as part of the application version. Please update to the latest version of cfn-lint or update the spec files manually (cfn-lint -u)

[PatMyron]

Good catch, reproduced:

Period (30) not supported for namespaces with the following prefix: AWS/ (Service: AmazonCloudWatch; Status Code: 400; Error Code: ValidationError; Request ID: )

Resources:
  Alarm:
    Type: AWS::CloudWatch::Alarm
    Properties:
      ComparisonOperator: GreaterThanOrEqualToThreshold
      EvaluationPeriods: 2
      Period: 30
      MetricName: HTTPCode_ELB_5XX_Count
      Namespace: AWS/ApplicationELB

Wondering if that limitation is specific to the AWS/ prefix from that error message and if it lines up with any of our existing concise constraint formats