Cloudformation stack with nested resources fails to create - amazon-web-services

Question

I'm trying to define some common resources (specifically, a couple of IAM roles) that will be shared between two environments, via a nested stack. The first environment to use the nested stack's resources creates ok, but the second one fails when trying to run the nested stack. Am I not understanding something about how nested stacks work, or am I just doing something wrong?
My nested stack is defined as:
AWSTemplateFormatVersion: '2010-09-09'
Description: Defines common resources shared between environments.
Parameters:
ParentStage:
Type: String
Description: The Stage or environment name.
Default: ""
ParentVpcId:
Type: "AWS::EC2::VPC::Id"
Description: VpcId of your existing Virtual Private Cloud (VPC)
Default: ""
Resources:
LambdaFunctionSG:
Type: AWS::EC2::SecurityGroup
Properties:
GroupDescription: Identifies Lamdba functions to VPC resources
GroupName: BBA-KTDO-SG-LambdaFunction
VpcId: !Ref ParentVpcId
RdsAccessSG:
Type: AWS::EC2::SecurityGroup
Properties:
GroupDescription: Allows Lambda functions access to RDS instances
GroupName: BBA-KTDO-SG-RDS
SecurityGroupIngress:
- IpProtocol: tcp
FromPort: 3306
ToPort: 3306
SourceSecurityGroupId: !Ref LambdaFunctionSG
VpcId: !Ref ParentVpcId
I've uploaded that YAML file to an S3 bucket, and I'm then trying to use it in two separate stack files (i.e. app_dev.yaml and app_prod.yaml) as:
Resources:
CommonResources:
Type: 'AWS::CloudFormation::Stack'
Properties:
TemplateURL: "https://my-buildbucket.s3-eu-west-1.amazonaws.com/common/common.yaml"
Parameters:
ParentStage: !Ref Stage
ParentVpcId: !Ref VpcId
And referring to its outputs as (e.g):
VpcConfig:
SecurityGroupIds:
- !GetAtt [ CommonResources, Outputs.LambdaFunctionSGId ]
The first environment creates fine, including the nested resources. When I try to run the second environment, it fails with error:
Embedded stack
arn:aws:cloudformation:eu-west-1:238165151424:stack/my-prod-stack-CommonResources-L94ZCIP0UD9W/f9d06dd0-994d-11eb-9802-02554f144c21
was not successfully created: The following resource(s) failed to
create: [LambdaExecuteRole, LambdaFunctionSG].
Is it not possible to share a single resource definition between two separate stacks like this, or have I just missed something in the implementation?

Answer 1

As #jasonwadsworth mentioned that's correct names of the stacks are always amended with a random string at the end AWS::CloudFormation::Stack check the return values. Use GetAtt to get the name of the stack and construct the output. How do I pass values between nested stacks within the same parent stack in AWS CloudFormation?
Plus use aws cloudformation package command for packaging the nested stacks, no need to manually upload them to s3 bucket.
someting like
aws cloudformation package \
--template-file /path_to_template/template.json \
--s3-bucket bucket-name \
--output-template-file packaged-template.json
Take a look on the cloudformation output exports as well in case you are curious Difference between an Output & an Export