AWS Nested Stack Project

A sample project that deploys an AWS lambda function and a DynamoDb table using nested stacks in SAM. All resources are deployed using a nested stack. The nested stack is split into two resources;

Stack 1 -> The DynamoDb resource.
Stack 2 -> The Lambda resource.

Take a look at the parent stack found under the CloudFormation folder-> application-stack.yml.

This file look something like this..

AWSTemplateFormatVersion: '2010-09-09'
Transform: AWS::Serverless-2016-10-31
Description: aws nested stack example

Resources:
  DynamoDbStack:
    Type: AWS::CloudFormation::Stack
    Properties:
      TemplateURL: ./Resources/nested-stack-dynamodb.yml

  LambdaStack:
    Type: AWS::CloudFormation::Stack
    Properties:
      TemplateURL: ./Resources/nested-stack-lambda.yml
      Parameters:
        DynamoDbTable: !GetAtt DynamoDbStack.Outputs.TableName
    DependsOn: DynamoDbStack
    
 Outputs:
  LambdaFunctionName:
    Description: The name of the Lambda function
    Value: !GetAtt LambdaStack.Outputs.LambdaFunctionArn

Install using AWS SAM CLI:

Once you have edited your template and code you can deploy your application using the AWS SAM CLI Tool from the command line.

Install AWS SAM CLI if not already installed.

    https://docs.aws.amazon.com/serverless-application-model/latest/developerguide/install-sam-cli.html

If already installed check if new version is available.

    Follow steps to update cli version
    https://docs.aws.amazon.com/serverless-application-model/latest/developerguide/install-sam-cli.html

    Verify the installation.
    $ sam --version

Build & Deploy resources to AWS

    navigate to the CloudFormation folder in command prompt
    $ cd "AWS.Nested.Stacks/CloudFormation"

    Build package
    $ sam build -t application-stack.yml

    Deploy package
    Note: Once the package has been built... you will need to navigate to the newly created build folder, found in ./.aws-sam/build

    $ cd .aws-sam\build
    The exit deployment into CloudFormation in AWS... running either statement.

    $ sam deploy -t template.yaml --stack-name nested-stack-poc-jono --capabilities CAPABILITY_IAM CAPABILITY_AUTO_EXPAND

    OR 

    $ sam deploy -t template.yaml -g --capabilities CAPABILITY_IAM CAPABILITY_AUTO_EXPAND

Install using Azure DevOps Pipelines:

Below are the following steps you will need to deploy via CICD pipeline using Azure DevOps Pipelines

Step 1:

Update the codeUri field in the nested-stack-lambda.yml file to the following value. This is for the CICD pipeline to find the code location, in order to build the Lambda project. In the Release pipeline we will add a step to replace the #{System.DefaultWorkingDirectory}# token.

CodeUri: '#{System.DefaultWorkingDirectory}#/_AWS.Nested.Stacks/AWS.Nested.Stacks'

Step 2:

You will need to add your code to a repository in Azure Devops. Your repository should look like this;

Next create a new Pipeline where you will publish the project artefacts. See example below;

trigger:
- master

pool:
  vmImage: ubuntu-latest

steps:
- checkout: self

- task: PublishBuildArtifacts@1
  displayName: Publish AWS.Nested.Stacks Project
  condition: succeededOrFailed()
  inputs:
    PathtoPublish: 'AWS.Nested.Stacks'
    ArtifactName: 'AWS.Nested.Stacks'
    publishLocation: 'Container'

- task: PublishBuildArtifacts@1
  displayName: Publish Cloudformation
  condition: succeededOrFailed()
  inputs:
    PathtoPublish: 'CloudFormation'
    ArtifactName: 'CloudFormation'
    publishLocation: 'Container'

Step 3:

Create the Release pipeline. We need to add 3 tasks to our pipeline and should look like this when you finished;

Replace token in nested-stack-lambda.yml mentioned in Step 1, with the yaml looking something like this;

steps:
- task: qetza.replacetokens.replacetokens-task.replacetokens@5
  displayName: 'Replace tokens in nested-stack-lambda.yml'
  inputs:
    rootDirectory: '$(System.DefaultWorkingDirectory)/_AWS.Nested.Stacks/CloudFormation/Resources'
    targetFiles: 'nested-stack-lambda.yml'

Next step is to build the package using the AWS Shell Script task and point it to the parent application stack template application-stack.yml.

steps:
- task: AmazonWebServices.aws-vsts-tools.AWSShellScript.AWSShellScript@1
  displayName: 'AWS Shell Script - SAM Build Package'
  inputs:
    awsCredentials: 'AWS Credentials'
    regionName: 'AWS Region'
    scriptType: inline
    inlineScript: |
     sam.cmd build -t application-stack.yml
     
    disableAutoCwd: true
    workingDirectory: '$(System.DefaultWorkingDirectory)/_AWS.Nested.Stacks/CloudFormation'

The final step is to deploy the package also using the AWS Shell Script task. This time pointing it to the newly packaged template file template.yaml that will created under the .\CloudFormation\.aws-sam\build folder.