AWS cloudformation condition for creating a resource

Question

How to use a condition for AWS Child resource type

I wanted to create an AWS backup plan with 2 backup rules with a condition (example, if I set create2backup rule as "true", it should create the rule 1 and rule 2, if the condition is false, it should ignore creating the second rule and it should create the rule 1.

Condition - create rule is true --- Creates Rule 1 and Rule 2

Condition - create rule is false --- Creates Rule1 and should ignore creating rule 2 and exit

whatever thee condition is it should create the Rule 1, the condition should only apply to Rule 2.

Try1 :
BackupPlan:
    Type: AWS::Backup::BackupPlan
    Properties:
      BackupPlan: 
        BackupPlanName: backupplan
        BackupPlanRule:
          -  
            RuleName: !Ref RuleName   
          - <Some condition>
            RuleName: !Ref RuleName2



Try2:
StorageBackupPlan:
    Type: AWS::Backup::BackupPlan
   # DependsOn: StorageBackupVault
    Properties:
      BackupPlan: 
        BackupPlanName: !Ref BackupPlanName
        BackupPlanRule:
          !If
            - Createbackuprule2
            - 
              RuleName: !Ref RuleName
              
            - 
              RuleName: !Ref RuleName2
              

Error for try 2 - Properties validation failed for resource StorageBackupPlan with message: #/BackupPlan/BackupPlanRule: expected type: JSONArray, found: JSONObject

Try 3 : worked but not as I expected, if condition is true it creates rule 1 if the condition is false it creates rule 2 - got this from below answer

StorageBackupPlan:
    Type: AWS::Backup::BackupPlan
   # DependsOn: StorageBackupVault
    Properties:
      BackupPlan: 
        BackupPlanName: !Ref BackupPlanName
        BackupPlanRule:
          !If
            - Createbackuprule2 
            -
              - RuleName: !Ref RuleName1
            -
              - RuleName: !Ref RuleName2

"I couldn't use the condition there, it thrown error" - what error exactly? What did you actually try? — Marcin, Oct 26 '21 at 06:26
I used the condition there and it thrown error saying "Condition: CreateNewRole" property is not expected here — user9488542, Oct 26 '21 at 19:56

Dunedan · Answer 1 · 2021-10-27T10:58:05.293

1

You should be able to achieve the desired result by using the intrinsic Fn:If condition function like that:

Parameters:
  CreateNewRole:
    Type: String
    AllowedValues:
      - yes
      - no
  RuleName:
    Type: String
  RuleName2:
    Type: String

Conditions:
  CreateNewRoleCondition:
    !Equals
      - !Ref CreateNewRole
      - yes

Resources:
  MyBackupPlan:
    Type: AWS::Backup::BackupPlan
    Properties:
      BackupPlan:
        BackupPlanName: backupplan
        BackupPlanRule:
          !If
            - CreateNewRoleCondition
            -
              - RuleName: !Ref RuleName
              - RuleName: !Ref RuleName2
            -
              - RuleName: !Ref RuleName

edited Oct 27 '21 at 10:58

answered Oct 26 '21 at 20:13

Dunedan

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That given below error ```Properties validation failed for resource StorageBackupPlan with message: #/BackupPlan/BackupPlanRule: expected type: JSONArray, found: JSONObject``` – user9488542 Oct 27 '21 at 03:29
Are you sure you're using the same syntax as in my example? Mind the nested lists in the if condition. – Dunedan Oct 27 '21 at 05:22
Actually that worked @Dunedan, thank you. but sorry I haven't asked my question right. Update my requirement above. – user9488542 Oct 27 '21 at 06:37
I updated the answer now to reflect your new requirements. – Dunedan Oct 27 '21 at 10:58
Thank you, much appreciated. It worked. – user9488542 Oct 27 '21 at 15:43

AWS cloudformation condition for creating a resource

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