Confused about how to properly create nested cloudformation stacks - amazon-web-services

Question

Up until now, for my project, I had just a single cloudformation stack template. However, I recently encountered that limit for the number of bytes you can have in a stack template, which is why I've been looking into nested stacks. I'm having a bit of trouble wrapping my head around the formatting though, because I've seen a lot of differences in the examples provided.
Below is a snippet of the original (non-nested) stack template before hitting the limit.
---
AWSTemplateFormatVersion: "2010-09-09"
Description: "Template for wgs-pipeline"
Parameters:
CloudspanLambdaFuncS3BucketName:
Type: String
CloudspanLambdaFuncS3KeyName:
Default: 'sfn.deployable.zip'
Type: String
CloudspanLambdaFuncModuleName:
Default: 'cloudspan'
Type: String
Resources:
VPC:
Type: AWS::EC2::VPC
Properties:
CidrBlock: 10.0.0.0/16
InternetGateway:
Type: AWS::EC2::InternetGateway
RouteTable:
Type: AWS::EC2::RouteTable
Properties:
VpcId: !Ref 'VPC'
VPCGatewayAttachment:
Type: AWS::EC2::VPCGatewayAttachment
Properties:
VpcId: !Ref 'VPC'
InternetGatewayId: !Ref 'InternetGateway'
SecurityGroup:
Type: AWS::EC2::SecurityGroup
Properties:
GroupDescription: EC2 Security Group for instances launched in
the VPC by Batch
VpcId: !Ref 'VPC'
# Lambda Resources (the section I want to place in a separate stack)
CloudspanLambdaExecutionRole:
Type: "AWS::IAM::Role"
Properties:
AssumeRolePolicyDocument:
Version: "2012-10-17"
Statement:
- Effect: Allow
Principal:
Service: lambda.amazonaws.com
Action: "sts:AssumeRole"
Policies:
- PolicyName: CanListBuckets
PolicyDocument:
Version: "2012-10-17"
Statement:
- Effect: Allow
Action:
- "s3:GetBucketLocation"
- "s3:ListAllMyBuckets"
Resource: "arn:aws:s3:::*"
- PolicyName: CanLog
PolicyDocument:
Version: '2012-10-17'
Statement:
- Effect: Allow
Action:
- logs:*
Resource: arn:aws:logs:*:*:*
CloudspanLambdaFunction:
Type: "AWS::Lambda::Function"
Properties:
Handler:
Fn::Join: [ ".", [ Ref: CloudspanLambdaFuncModuleName, "handler"] ]
Role:
Fn::GetAtt: [ CloudspanLambdaExecutionRole, Arn ]
Code:
S3Bucket:
Ref: CloudspanLambdaFuncS3BucketName
S3Key:
Ref: CloudspanLambdaFuncS3KeyName
Runtime: "python3.6"
Timeout: "60"
What I want to do is isolate everything under the "Lambda resources" comment into a separate stack ("lambda stack") and then have this master stack call to that separate "lambda stack".
Below is my current set-up attempt, but I don't know if I'm doing it correctly:
Master template:
---
AWSTemplateFormatVersion: "2010-09-09"
Description: "Master template for wgs-pipeline. Contains network resources, lambda parameters, and batch
parameters"
Parameters:
CloudspanLambdaFuncS3BucketName:
Type: String
CloudspanLambdaFuncS3KeyName:
Default: 'sfn.deployable.zip'
Type: String
CloudspanLambdaFuncModuleName:
Default: 'cloudspan'
Type: String
Resources:
# The stuff that was already in the Resources section in the original stack
VPC:
Type: AWS::EC2::VPC
Properties:
CidrBlock: 10.0.0.0/16
InternetGateway:
Type: AWS::EC2::InternetGateway
RouteTable:
Type: AWS::EC2::RouteTable
Properties:
VpcId: !Ref 'VPC'
VPCGatewayAttachment:
Type: AWS::EC2::VPCGatewayAttachment
Properties:
VpcId: !Ref 'VPC'
InternetGatewayId: !Ref 'InternetGateway'
SecurityGroup:
Type: AWS::EC2::SecurityGroup
Properties:
GroupDescription: EC2 Security Group for instances launched in the VPC by Batch
VpcId: !Ref 'VPC'
# The section that is referencing a separate stack
LambdaStack:
Type: AWS::CloudFormation::Stack
Properties:
Parameters:
LambdaFunction:
# ref?
LambdaExecutionRole:
# ref?
TemplateURL: # URL to S3 location of lambda stack
TimeoutInMinutes: '60'
LambdaStack template:
---
AWSTEmplateFormatVersion: '2010-09-09'
Description: Lambda functions stack, contains lambda function and lambda function execution roles.
Parameters:
LambdaFunction:
Description: the lambda function.
LambdaExecutionRole:
Description: the lambda execution roles.
Resources:
Type: "AWS::Lambda::Function"
Properties:
Handler:
#
# Need to figure out how to reference these since they are parameters that exist in the master template
#
Fn::Join: [ ".", [ Ref: CloudspanLambdaFuncModuleName, "handler"] ]
Role:
Fn::GetAtt: [ CloudspanLambdaExecutionRole, Arn ]
Code:
S3Bucket:
Ref: CloudspanLambdaFuncS3BucketName
S3Key:
Ref: CloudspanLambdaFuncS3KeyName
Runtime: "python3.6"
Timeout: "60" # This will be included in the master stack?
Outputs:
LambdaStack:
Description: Lambda stack ID.
Value:
Ref: LambdaFunction
Export:
Name:
Fn::Sub: "${AWS::StackName}-LambdaFunction"
LambdaExecutionRoleStack:
Description: Lambda execution role stack ID.
Value:
Ref: LambdaExecutionRole
Export:
Name:
Fn::Sub: "${AWS::StackName}-LambdaExecutionRole"
Have I formatted the LambdaStack template and master template correctly so far? An in terms of the CloudspanLambdaFunction and CloudspanLambdaExecutionRole parameters that were in the original (un-nested) stack, how exactly do I format those in the LambdaStack (nested) template? Would it be just adding the two parameters under the resources section of the LambdaStack yaml?