CloudFormation Template with Reference or TopLevel Fn::FindInMap

Question

I have the following mapping defined in my template

"Mappings": {
"TimeBasedAutoScale"  : {
  "days" : {
    "weekend" : {"0":"off","1":"off","2":"off","3":"off","4":"off","5":"off","6":"off","7":"off","8":"off","9":"off","10":"off","11":"off","12":"off","13":"off","14":"off","15":"off","16":"off","17":"off","18":"off","19":"off","20":"off","21":"off","22":"off","23":"off"},
    "weekday1" : {"0":"off","1":"off","2":"on","3":"on","4":"on","5":"on","6":"on","7":"on","8":"on","9":"on","10":"on","11":"on","12":"on","13":"on","14":"on","15":"on","16":"on","17":"on","18":"on","19":"on","20":"on","21":"on","22":"off","23":"off"},
    "weekday2" : {"0":"off","1":"off","2":"off","3":"on","4":"on","5":"on","6":"on","7":"on","8":"on","9":"on","10":"on","11":"on","12":"on","13":"on","14":"on","15":"on","16":"on","17":"on","18":"on","19":"on","20":"on","21":"on","22":"off","23":"off"}
  }
},
"TimeBasedSchedule": {
  "6AMTimeBasedSchedule" : {
    "schedule" : {
      "Monday" : { "Fn::FindInMap" : [ "TimeBasedAutoScale", "days", "weekday1"]},
      "Tuesday" : { "Fn::FindInMap" : [ "TimeBasedAutoScale", "days", "weekday1"]},
      "Wednesday" :{ "Fn::FindInMap" : [ "TimeBasedAutoScale", "days", "weekday1"]},
      "Thursday" : { "Fn::FindInMap" : [ "TimeBasedAutoScale", "days", "weekday1"]},
      "Friday" : { "Fn::FindInMap" : [ "TimeBasedAutoScale", "days", "weekday1"]},
      "Saturday" : { "Fn::FindInMap" : [ "TimeBasedAutoScale", "days", "weekend"]}, 
     "Sunday" : { "Fn::FindInMap" : [ "TimeBasedAutoScale", "days", "weekend"]}
  }
},
"7AMTimeBasedSchedule" : {
  "schedule" :  {
    "Monday" : { "Fn::FindInMap" : [ "TimeBasedAutoScale", "days", "weekday1"]},
    "Tuesday" : { "Fn::FindInMap" : [ "TimeBasedAutoScale", "days", "weekday1"]},
    "Wednesday" :{ "Fn::FindInMap" : [ "TimeBasedAutoScale", "days", "weekday1"]},
    "Thursday" : { "Fn::FindInMap" : [ "TimeBasedAutoScale", "days", "weekday1"]},
    "Friday" : { "Fn::FindInMap" : [ "TimeBasedAutoScale", "days", "weekday1"]},
    "Saturday" : { "Fn::FindInMap" : [ "TimeBasedAutoScale", "days", "weekend"]}, 
    "Sunday" : { "Fn::FindInMap" : [ "TimeBasedAutoScale", "days", "weekend"]}
  }
}}

However, validation fails and after looking at the docs I can see why. The mapping function wants a three tiered key and the value can only be a string or a list.

Is there anyway to do the above with a reference or better mapping?

Answer 1

To accomplish a multi-level mapping, apply your nested Fn::FindInMap intrinsic functions in the Resources or Outputs section directly.

Here's a complete working version of your example:

{
  "Description": "Return 'on' or 'off' according to the provided schedule, hour of day, and day of week.",
  "Mappings": {
    "TimeBasedAutoScale": {
      "weekend" : {"0":"off","1":"off","2":"off","3":"off","4":"off","5":"off","6":"off","7":"off","8":"off","9":"off","10":"off","11":"off","12":"off","13":"off","14":"off","15":"off","16":"off","17":"off","18":"off","19":"off","20":"off","21":"off","22":"off","23":"off"},
      "weekday1" : {"0":"off","1":"off","2":"on","3":"on","4":"on","5":"on","6":"on","7":"on","8":"on","9":"on","10":"on","11":"on","12":"on","13":"on","14":"on","15":"on","16":"on","17":"on","18":"on","19":"on","20":"on","21":"on","22":"off","23":"off"},
      "weekday2" : {"0":"off","1":"off","2":"off","3":"on","4":"on","5":"on","6":"on","7":"on","8":"on","9":"on","10":"on","11":"on","12":"on","13":"on","14":"on","15":"on","16":"on","17":"on","18":"on","19":"on","20":"on","21":"on","22":"off","23":"off"}
  },
    "TimeBasedSchedule": {
      "6AMTimeBasedSchedule": {
        "Monday": "weekday1",
        "Tuesday": "weekday1",
        "Wednesday": "weekday1",
        "Thursday": "weekday1",
        "Friday": "weekday1",
        "Saturday": "weekend",
        "Sunday": "weekend"
      },
      "7AMTimeBasedSchedule": {
        "Monday": "weekday2",
        "Tuesday": "weekday2",
        "Wednesday": "weekday2",
        "Thursday": "weekday2",
        "Friday": "weekday2",
        "Saturday": "weekend",
        "Sunday": "weekend"
      }
    }
  },
  "Parameters": {
    "Schedule": {
      "Description": "Selected schedule",
      "Type": "String",
      "AllowedValues" : [ "6AMTimeBasedSchedule", "7AMTimeBasedSchedule" ],
      "Default": "6AMTimeBasedSchedule"
    },
    "DayOfWeek": {
      "Description": "Day of week",
      "Type": "String",
      "AllowedValues" : [ "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday", "Sunday" ],
      "Default": "Monday"
    },
    "HourOfDay": {
      "Description": "Hour of Day",
      "Type": "Number",
      "MinValue": "0",
      "MaxValue": "23",
      "Default": "0"
    }
  },
  "Resources": {
    "Dummy": {
      "Type": "AWS::CloudFormation::WaitConditionHandle"
    }
  },
  "Outputs": {
    "Result": {
      "Value": {
        "Fn::FindInMap": [
          "TimeBasedAutoScale",
          {"Fn::FindInMap": ["TimeBasedSchedule", "6AMTimeBasedSchedule", {"Ref": "DayOfWeek"}]},
          {"Ref": "HourOfDay"}
        ]
      }
    }
  }
}