Working Alarm template with cloudformation Fn::ForEach

cloudformation-language-extensions-fn-foreach.yaml

AWSTemplateFormatVersion: 2010-09-09
Transform: AWS::LanguageExtensions

Parameters:
  AlarmLambdaPairs:
    Type: CommaDelimitedList
    Description: |
      Comma-separated "prefix:lambdaName" pairs. Example: "PrefixA:MyLambdaA,PrefixB:MyLambdaB"
    Default: PrefixA:MyLambdaA,PrefixB:MyLambdaB

Resources:
  # This special resource logical ID "Fn::ForEach::CreateAlarms"
  # triggers the loop expansion in Language Extensions.
  Fn::ForEach::CreateAlarms:
    # The array below must have exactly three items:
    # 1) The iteration variable name (Pair),
    # 2) The list to iterate over (AlarmLambdaPairs),
    # 3) A map of resource definitions keyed by a name that references the iteration variable.
    - Pair
    - !Ref AlarmLambdaPairs
    # The &{} syntax allows non-alphanumeric characters in the Collection to be used in OutputKey parameter
    - MyAlarm&{Pair}:
        Type: AWS::CloudWatch::Alarm
        Properties:
          AlarmName: !Sub
            - ${Value0}-${Value1}
            - Value0: !Select [0, !Split [':', !Ref Pair]]
              Value1: !Select [1, !Split [':', !Ref Pair]]

          MetricName: Errors
          Namespace: AWS/Lambda
          Dimensions:
            - Name: FunctionName
              Value: !Select [1, !Split [':', !Ref Pair]]

          Statistic: Sum
          Period: 60
          EvaluationPeriods: 1
          Threshold: 1
          ComparisonOperator: GreaterThanOrEqualToThreshold

          AlarmDescription: !Sub
            - 'Alarm for Lambda: ${LambdaName}'
            - LambdaName: !Select [1, !Split [':', !Ref Pair]]