CloudFormation Joining List of Strings with FindInMap - amazon-web-services

Question

I am facing issue with Cloudformation on joining a list of strings after getting it from a map.
Error caused is Security Group expects a list of string.
"123456":
us-east-1:
#VPC1
VpcId: vpc-xxxx
VpcCidr: 10.78.160.0/20
SecurityGroups: sg-123
AvailabilityZones: us-east-1a,us-east-1b,us-east-1c
"123457":
us-east-1:
#VPC
VpcId: vpc-xxxx
VpcCidr: 10.78.160.0/20
SecurityGroups: sg-123,sg-124
AvailabilityZones: us-east-1a,us-east-1b,us-east-1c
LaunchConfig:
Type: AWS::AutoScaling::LaunchConfiguration
Metadata:
AWS::CloudFormation::Init:
config:
Properties:
InstanceType:
Ref: InstanceType
SecurityGroups: !Join [ ",", [!FindInMap [!Ref "AWS::AccountId", !Ref "AWS::Region", SecurityGroups], !Ref EC2SG ]]
IamInstanceProfile:
please let me know how to get the list for securitygroups and adding it to another resource
Solved by using this question
How do I use nested lists or append to a list in Cloudformation?

Answer 1

Lets take mappings:
Mappings:
"111222333444":
us-east-1:
SecurityGroups:
- sg-abc
- sg-xyz
us-west-2:
SecurityGroups:
- sg-1234
- sg-3456
Security groups can be referred as
SecurityGroupIds:
"Fn::FindInMap":
[!Ref AWS::AccountId, !Ref AWS::Region, SecurityGroups]
Define as array in mappings and pass the full array, this way we can avoid splitting and joining.
Full Template , tested on a Lambda
AWSTemplateFormatVersion: "2010-09-09"
Description: "Test"
Mappings:
"111222333444":
us-east-1:
SecurityGroups:
- sg-abc
- sg-xyz
us-west-2:
SecurityGroups:
- sg-1234
- sg-3456
Resources:
TestLambda:
Type: "AWS::Lambda::Function"
Properties:
Handler: com.test.MainClass::handleRequest
Runtime: java8
FunctionName: "Test-Lambda"
Code:
S3Bucket: code-bucket
S3Key: !Sub "artifacts/test.jar"
Description: "Test Lambda"
MemorySize: 512
Timeout: 60
Role: !Ref my-role-arn
VpcConfig:
SecurityGroupIds:
"Fn::FindInMap":
[!Ref AWS::AccountId, !Ref AWS::Region, SecurityGroups]
SubnetIds:
- subnet-1
- subnet-2