Software Engineering

How to Create CloudFormation with Multiple Files


To create a CloudFormation (CFN) stack with multiple files, you can follow these general steps:

  1. Organize your resources: Divide your resources into logical groups or services. For example, you might have separate files for networking, storage, compute, and so on.

  2. Create YAML or JSON templates: Create individual YAML or JSON templates for each group or service. Each template will define the resources specific to that group. For example, networking.yaml, storage.yaml, and compute.yaml.

  3. Define the dependencies: Determine the dependencies between the resources in different templates. For example, your compute resources might depend on networking resources.

  4. Create a main template: Create a main CFN template that serves as the entry point for creating the stack. This template will reference the individual templates created in step 2.

  5. Reference the templates in the main template: In the main template, use the AWS::CloudFormation::NestedStack resource to reference the individual templates. Specify the path or S3 URL to the templates.

  6. Define the parameters: Define any necessary parameters in the main template or the individual templates. Parameters allow you to customize the stack during deployment.

  7. Deploy the stack: Use the AWS Management Console, AWS CLI, or AWS SDKs to deploy the CFN stack. Provide the main template file as input for the deployment.

  8. Validate the stack: Validate the stack to ensure there are no syntax errors or resource conflicts. You can use the AWS CLI or AWS Management Console for validation.

  9. Monitor the stack creation: Monitor the stack creation process to track the progress and identify any errors or issues. You can view the CloudFormation events or logs for troubleshooting.

By following these steps, you can create a CloudFormation stack that consists of multiple files, allowing you to manage and organize your infrastructure resources effectively.

How do you run it once created?

Once you have created a CloudFormation stack, you can run it by executing an update or create operation. The specific command or action you need to take depends on whether the stack is already created or if you are updating an existing stack.

Here are the steps to run a CloudFormation stack:

  1. Determine the stack’s current status: Use the AWS Management Console, AWS CLI, or AWS SDKs to check the current status of the stack. This step is optional but can help you understand the stack’s current state and whether it needs to be created or updated.

  2. Update the stack (if it already exists): If the stack already exists, you can update it by making changes to the CloudFormation template or its parameters. Use the appropriate command or action based on the AWS service you are using:

  • AWS Management Console: Go to the CloudFormation service, select the stack, and click on “Update Stack.” Upload the updated template file if necessary and provide any updated parameters.

  • AWS CLI: Use the aws cloudformation update-stack command, providing the stack name, updated template file if necessary (--template-body or --template-url), and any updated parameters (--parameters).

  1. Create the stack (if it doesn’t exist): If the stack doesn’t exist yet, you can create it by running the CFN template. Again, use the appropriate command or action based on the AWS service you are using:
  • AWS Management Console: Go to the CloudFormation service, click on “Create Stack,” and upload the CFN template. Provide any necessary parameters for the stack.

  • AWS CLI: Use the aws cloudformation create-stack command, providing the stack name, template file (--template-body or --template-url), and any required parameters (--parameters).

  1. Monitor the stack creation/update: Monitor the progress of the stack creation or update process. You can check the CloudFormation events or logs to track the progress and identify any errors or issues.

  2. Wait for the stack to complete: Depending on the complexity of the stack, it may take some time to create or update. You can use the AWS Management Console, AWS CLI, or AWS SDKs to periodically check the stack status until it reaches a stable state (e.g., CREATE_COMPLETE, UPDATE_COMPLETE).

Once the stack creation or update is complete, your resources should be provisioned or modified according to the CloudFormation template. You can then proceed to use or manage those resources as needed.

Show me some code!

Here’s an example of how you can use the AWS CLI to create and update a CloudFormation stack with multiple files:

  1. Create a main template file (main-template.yaml) that references the individual templates:
Resources:
  NetworkingStack:
    Type: AWS::CloudFormation::NestedStack
    Properties:
      TemplateURL: s3://bucket-name/networking.yaml

  StorageStack:
    Type: AWS::CloudFormation::NestedStack
    Properties:
      TemplateURL: s3://bucket-name/storage.yaml

  ComputeStack:
    Type: AWS::CloudFormation::NestedStack
    Properties:
      TemplateURL: s3://bucket-name/compute.yaml
  1. Create individual templates for networking, storage, and compute. Here’s an example of the networking.yaml file:
Resources:
  VPC:
    Type: AWS::EC2::VPC
    Properties:
      ...
  Subnet:
    Type: AWS::EC2::Subnet
    Properties:
      ...
  ...
  1. Upload the individual template files (networking.yaml, storage.yaml, compute.yaml) to an S3 bucket. Replace “bucket-name” with your actual S3 bucket name in the main template.

  2. Use the AWS CLI to create or update the stack. Open your terminal or command prompt and execute the following command:

# To create a stack
aws cloudformation create-stack --stack-name my-stack --template-body file://main-template.yaml

# To update a stack
aws cloudformation update-stack --stack-name my-stack --template-body file://main-template.yaml

Make sure to replace “my-stack” with the desired stack name and adjust the file path to the location of your main-template.yaml file.

Note: If your templates are already located in an S3 bucket, you can use --template-url instead of --template-body in the CLI commands, providing the S3 URL of the main template.

That’s a basic example of how you can create and update a CloudFormation stack with multiple files using the AWS CLI. Remember to adapt the templates and commands to your specific use case and file locations.