Multiple conditions in cloud formation resource creation

Question

I'm using a platform condition to control the type of environment that gets spun up on AWS. There are plenty of shared resources, but I need certain EC2 instances with pre-baked AMIs depending on a number conditions.

"Parameters": {
"Platform": {
  "Description": "Select platform type - linux or windows",
  "Default": "linux",
  "Type": "String",
  "AllowedValues": [ "linux", "windows", "both" ],
  "ConstraintDescription": "Must enter either linux, windows, or both"
},

Then I set the conditions.

"Conditions" : {
  "LinuxPlatform" : {"Fn::Equals" : [{"Ref" : "Platform"}, "linux"]},
  "WindowsPlatform" : {"Fn::Equals" : [{"Ref" : "Platform"}, "windows"]},
  "BothPlatform" : {"Fn::Equals" : [{"Ref" : "Platform"}, "both"]}
},

In a resource I'd like to use either linux or windows to trigger a Windows or Linux Ec2 creation, or use both to deploy every ec2 resource declared.

I've tried the following using fn:or in a few ways.

"Fn::Or": [{"Condition": "LinuxPlatform"}, {"Condition": "BothPlatform" }],

and...

"Condition" : {
   "Fn::Or" : [
      {"Condition" : "LinuxPlatform"},
      {"Condition" : "BothPlatform"}
   ]
}

I keep getting the following error when trying to deploying and validating using the aws cli.

aws cloudformation validate-template --template-body       file://./cloudformation/deploy.json

A client error (ValidationError) occurred when calling the ValidateTemplate operation: Template format error: Every Condition member must be a string.

Is it possible to evaluate multiple conditions to control resource creation? If not are there any alternatives I could try?

Solution 1

Try adding

"MyCondition": {"Fn::Or": [{"Condition": "LinuxPlatform"}, {"Condition": "BothPlatform" }]}

to the bottom of your Conditions like that:

    "Conditions" : {
        "LinuxPlatform" : {"Fn::Equals" : [{"Ref" : "Platform"}, "linux"]},
        "WindowsPlatform" : {"Fn::Equals" : [{"Ref" : "Platform"}, "windows"]},
        "BothPlatform" : {"Fn::Equals" : [{"Ref" : "Platform"}, "both"]},
        "MyCondition": {"Fn::Or": [{"Condition": "LinuxPlatform"}, {"Condition": "BothPlatform" }]}
    },

Solution 2

I was looking for the same thing with different scenarios in the YAML format. Below is the YAML format for the reference.

CreateResources: !Or [!Equals [!Ref "Environment", prod], !Equals [!Ref "Environment", dev], !Equals [!Ref "Environment", preprod], !Equals [!Ref "Environment", test]]

example

---
AWSTemplateFormatVersion: 2010-09-09
Description: 'AWS cloudformation template bucket. '
Parameters:
  Environment:
    Description: Enter the environmet name from allowed values
    Type: String
    AllowedValues:
      - qa
      - dev
      - prod
      - stage
Conditions:
    Prod: !Equals [ !Ref Environment, production]
    dev: !Equals [ !Ref Environment, dev]
    stage: !Equals [ !Ref Environment, stage]
    qa: !Equals [ !Ref Environment, qa]
    CreateResources: !Or [!Equals [!Ref "Environment", prod], !Equals [!Ref "Environment", dev], !Equals [!Ref "Environment", preprod], !Equals [!Ref "Environment", test]]

Resources:
  RenderEngineEFSSG:
    Type: AWS::EC2::SecurityGroup
    Condition: CreateResources
    Properties:
      GroupDescription:  test SG. 
      GroupName: !Join [ "-", [ !Ref Environment, sgname ] ]
      VpcId: vpc-0e4d5cad992b8d65b
      SecurityGroupIngress:
        - IpProtocol: tcp
          FromPort: 2049
          ToPort: 2049
          CidrIp: 0.0.0.0/0
          Description: Ingress Rule for Lambda to access EFS.
      SecurityGroupEgress: []

Comments

[Joe Gardiner]

Thanks, I'll try that shortly. The structure is that if I select windows from the drop down during stack creation it will create 50% of the EC2 resources in the template. If I select linux it's the other 50%. I want to be able to select both to have all the instances deployed, mainly for dev and test purposes. Would using the above allow me to do that, or would I need to add windows to the fn::or?

[Efren]

How is the proposed addition different to the one in the question?

[lznt]

@Efren It seems the "Condition" in the error message means the “Condition” under a “Resource”, which must be a SINGLE string.

[MD. RAKIB HASAN]

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