Using Python to Manage Third-party Resources in AWS CloudFormation.
Tags: aws, softwaredevelopment, product, webdev
Published: 2024-03-28 10:38:31

**Introduction**

Let’s begin with the question “what is AWS CloudFormation?”. In digital transformation and cloud computing, AWS CloudFormation is a powerful service that enables the management of infrastructure resources in the Amazon Web Services (AWS) Cloud. With AWS CloudFormation, you can describe and provision your entire cloud environment using JSON or YAML templates. While AWS CloudFormation offers a wide range of native resources, there are instances where you may need to manage third-party resources that are not natively supported. This is where Python and custom resources come into play.

In this comprehensive guide, we will explore how to use Python and AWS CloudFormation to manage third-party resources efficiently. We’ll delve into the intricacies of custom resources, resource types, and the crhelper framework. By leveraging these tools, you can extend the capabilities of AWS CloudFormation and integrate external services seamlessly into your infrastructure as code (IaC) deployments.

**Table Of Contents**

**1. Understanding the Need for Third-Party Resource Management in AWS CloudFormation**

- The Limitations of Native AWS Resources
- The Importance of Managing Third-Party Resources

**2. Introducing Custom Resources in AWS CloudFormation**

- The Role of Custom Resources
- Leveraging Lambda Functions for Custom Resource Logic
- Creating a Custom Resource with Python and Lambda

**3. Exploring Resource Types in AWS CloudFormation**

- The Advantages of Resource Types
- Developing Resource Types with the CloudFormation CLI
- Registering and Using Resource Types in Templates

**4. Simplifying Custom Resource Development with crhelper**

- Introducing crhelper: A Framework for Custom Resources
- Installing and Setting Up crhelper
- Writing Custom Resources with crhelper

**5. Managing Third-Party Resources: A Step-by-Step Guide**

- Setting Up the Development Environment
- Initializing the Custom Resource Provider
- Defining the Resource Schema
- Implementing the Custom Resource Handlers
- Testing and Deploying the Custom Resource

**6. Best Practices for Custom Resource and Resource Type Development**

- Ensuring Idempotency and Handling Updates
- Implementing Error Handling and Rollbacks
- Optimal Use of Permissions and IAM Roles

**7. Real-World Use Cases for Custom Resources and Resource Types**

- Managing GitHub Repositories with AWS CloudFormation
- Provisioning Third-Party Website Monitors
- Looking Up Amazon Machine Images (AMIs) Dynamically

**8. Comparing Custom Resources and Resource Types**

- Schema Definition and Visibility
- Language Support and Execution Location
- Development Workflow and Tooling

**9. Overcoming Security Risks with Terraform and AWS CloudFormation**

- Protecting Against Infrastructure as Code (IaC) Drift
- Securing Multi-Region Deployments with Terraform

**10. Conclusion**

- Unlocking the Power of Python and AWS CloudFormation
- Streamlining Third-Party Resource Management
- Achieving Efficiency and Security in IaC Deployments

**11. Additional Resources**

- Further Reading and Documentation
- GitHub Repositories and Examples

**12. Glossary**

- Key Terms and Definitions

**Understanding The Need For Third-Party Resource Management In AWS CloudFormation**

**The Limitations of Native AWS Resources**

AWS CloudFormation offers a vast array of native resources that allow you to provision and manage various AWS services. These resources cover a wide range of use cases, from creating EC2 instances to configuring S3 buckets. However, there are instances where you may require additional resources that are not natively supported by AWS CloudFormation.

For example, you might want to integrate a third-party software-as-a-service (SaaS) product into your infrastructure or provision on-premises resources in a hybrid environment. In such cases, relying solely on native AWS resources would be limiting and prevent you from fully leveraging the capabilities of AWS CloudFormation.


![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/grky2l5egp2k84aap3v5.jpg)

**The Importance of Managing Third-Party Resources**

Effectively managing third-party resources within your AWS CloudFormation deployments offers several benefits. Firstly, it allows you to maintain a unified infrastructure as code approach, where all resources, whether native or third-party, are defined and provisioned through AWS CloudFormation. This improves consistency, simplifies management, and enhances deployment automation.

Furthermore, managing third-party resources through AWS CloudFormation enables you to take advantage of the built-in benefits of AWS CloudFormation, such as rollback functionality in case of deployment failures. By treating third-party resources as integral parts of your infrastructure, you ensure that they are managed, versioned, and controlled alongside your native AWS resources.

**Introducing Custom Resources In AWS CloudFormation**

**The Role of Custom Resources**

Custom resources provide a mechanism to extend AWS CloudFormation beyond native resource types and provision any resource using custom logic. With custom resources, you can leverage AWS Lambda functions or Amazon Simple Notification Service (SNS) topics to implement the provisioning, updating, and deletion of third-party resources.

By utilizing custom resources, you can integrate external services, manage non-AWS resources, and perform any necessary configuration or setup within your AWS CloudFormation deployments. This flexibility expands the capabilities of AWS CloudFormation and allows you to create comprehensive, end-to-end infrastructure as code solutions.

**Leveraging Lambda Functions for Custom Resource Logic**

One of the key components in implementing custom resources is AWS Lambda. Lambda functions provide the necessary compute power to execute custom resource logic, making them a natural fit for custom resource development within AWS CloudFormation.

With Lambda, you can write code in various languages, including Python, to handle the creation, updating, and deletion of your custom resources. This code can interact with third-party APIs, perform data transformations, or execute any other necessary actions required to manage the resources effectively.

**Creating a Custom Resource with Python and Lambda**

To create a custom resource using Python and Lambda, you need to define the resource’s properties, implement the necessary Lambda function handlers, and integrate them with AWS CloudFormation.

Firstly, you define the custom resource in your AWS CloudFormation template using the AWS::CloudFormation::CustomResource type. This type requires a ServiceToken property, which specifies the ARN of the Lambda function that will handle the custom resource logic.

Next, you write the Lambda function code, which will be responsible for executing the custom resource’s create, update, delete, read, and list operations. This code should handle the input parameters from AWS CloudFormation, interact with the third-party API or resource, and provide a response back to AWS CloudFormation.

Finally, you package and deploy the Lambda function using the AWS Command Line Interface (CLI) or other deployment tools. Once deployed, you can use the custom resource in your AWS CloudFormation templates, just like any other native resource.

**Exploring Resource Types In AWS CloudFormation**

**The Advantages of Resource Types**

While custom resources provide a solution for managing third-party resources, there are some limitations in terms of visibility and integration with other AWS services. Resource types address these limitations by providing a more structured and integrated approach to managing third-party resources within AWS CloudFormation.

Resource types define a schema that explicitly declares the properties, inputs, and outputs of the resource. This schema provides visibility to AWS CloudFormation, enabling better validation of templates and integration with other AWS services like AWS Config.

By using resource types, you can treat third-party resources as first-class citizens within AWS CloudFormation, allowing for a more seamless and integrated infrastructure as code experience.

**Developing Resource Types with the CloudFormation CLI**

To create a resource type, you utilize the CloudFormation Command Line Interface (CLI) and follow a structured development workflow. The CLI provides tools and commands to generate the initial resource type project, define the resource type specification (schema), and write the necessary handler code.

The resource type specification defines the properties, attributes, and other metadata of the resource type. It also specifies the operations that the resource type can perform, such as create, update, delete, read, and list.

With the resource type specification in place, you can proceed to write the handler code for each operation. This code will be responsible for executing the necessary logic to manage the third-party resource.

Once the resource type specification and handler code are complete, you can register the resource type with the CloudFormation registry using the CLI. This step uploads the resource type to the registry and makes it available for use in AWS CloudFormation templates.

**Registering and Using Resource Types in Templates**

Once a resource type is registered, you can use it within your AWS CloudFormation templates just like any other native resource. You declare the resource type, provide the necessary properties and inputs, and AWS CloudFormation handles the provisioning, updating, and deletion of the resource.

The resource type handlers, written in Java, Go, or Python, are executed by AWS CloudFormation in response to lifecycle events. These handlers communicate directly with AWS CloudFormation and provide status updates, outputs, and any necessary data for the resource management process.

By leveraging resource types, you can achieve a more structured and integrated approach to managing third-party resources in AWS CloudFormation. This allows for better validation, visibility, and integration with other AWS services, resulting in more robust and scalable infrastructure as code deployments.


![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/5mu6r0x4asvr9rhpzrxq.jpg)

**Simplifying Custom Resource Development With Crhelper**

**Introducing crhelper: A Framework for Custom Resources**

While custom resources offer great flexibility, they can be challenging to develop and maintain due to the need for extensive error handling, signaling status, and managing responses. To simplify custom resource development, the crhelper framework comes to the rescue.

crhelper is an open-source project that provides a set of abstractions, utilities, and best practices for writing custom resources. It abstracts away the complexity of handling CloudFormation lifecycle events, response signaling, and error handling, allowing developers to focus on the core resource logic.

By leveraging crhelper, you can streamline the development process, improve code maintainability, and ensure adherence to best practices when creating custom resources for AWS CloudFormation.

**Installing and Setting Up crhelper**

To get started with crhelper, you need to install the framework and set up the necessary project structure. Using the Python package manager, pip, you can install crhelper into your project directory.

Once installed, you can create a new directory for your custom resource project and initialize it with crhelper. This sets up the project structure, including the necessary files and configurations for developing custom resources.

**Writing Custom Resources with crhelper**

With crhelper set up, you can start writing your custom resource handlers using the provided abstractions and utilities. crhelper offers decorators for each CloudFormation lifecycle event, such as create, update, delete, read, and list.

By decorating your resource handler functions with the appropriate decorators, you can define the logic for each lifecycle event. crhelper takes care of handling event payloads, signaling status to AWS CloudFormation, and managing error conditions.

Using crhelper greatly simplifies the code required to handle custom resource operations, making custom resource development more efficient, maintainable, and robust.

**Managing Third-Party Resources: A Step-By-Step Guide**

**Setting Up the Development Environment**

Before diving into custom resource development, it’s essential to set up your development environment. This involves installing the necessary tools, such as Python, AWS CLI, and the CloudFormation CLI.

To ensure compatibility, make sure you have Python 3.6 or later installed. You can download Python from the official website or use your operating system’s package manager.

Next, install the AWS CLI, which provides command-line access to AWS services. The AWS CLI allows you to interact with AWS CloudFormation, Lambda, and other necessary services.

Finally, install the CloudFormation CLI, a tool specifically designed for resource type development. The CloudFormation CLI simplifies the process of creating, testing, and deploying resource types.

**Initializing the Custom Resource Provider**

With your development environment ready, you can initialize the custom resource provider using the CloudFormation CLI. This command-line tool generates the initial project structure and files required for custom resource development.

By running the cfn init command and providing the desired project name, you can create a new directory with the necessary files for your custom resource provider.

**Defining the Resource Schema**

The resource schema is a crucial component of custom resource development. It defines the properties, attributes, and other metadata of the custom resource, providing visibility to AWS CloudFormation.

Using a text editor, open the generated resource schema file and define the necessary schema elements. Specify the resource type name, description, properties, and any other relevant information.

The resource schema serves as a blueprint for your custom resource, enabling AWS CloudFormation to validate templates, perform change sets, and integrate with other AWS services.


![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/mk62dqtp7xz5kmq7nnxc.jpg)

**Implementing the Custom Resource Handlers**

With the resource schema defined, it’s time to implement the custom resource handlers. These handlers are responsible for executing the logic associated with each lifecycle event of the custom resource.

Using the provided example code or starting from scratch, open the custom resource handler file in your preferred text editor. Write the necessary code for each lifecycle event, such as create, update, delete, read, and list.

Inside each handler function, you can access the request payload, perform the required operations on the third-party resource, and provide a response back to AWS CloudFormation.

**Testing and Deploying the Custom Resource**

Once you have implemented the custom resource handlers, it’s crucial to test them thoroughly before deploying the resource. Use the CloudFormation CLI’s testing capabilities to validate the behavior and correctness of your custom resource.

The CloudFormation CLI provides a test command that allows you to simulate lifecycle events and verify the responses and outputs of the custom resource handlers. Use this command to iterate and refine your custom resource implementation.

After successful testing, you can package and deploy the custom resource using the CloudFormation CLI’s package and deploy commands. These commands bundle the necessary files, upload them to AWS, and register the resource in the CloudFormation registry.

With the custom resource deployed, you can start using it in your AWS CloudFormation templates and leverage its functionality to manage third-party resources seamlessly.

**Best Practices For Custom Resource And Resource Type Development**

**Ensuring Idempotency and Handling Updates**

When developing custom resources or resource types, it’s crucial to ensure idempotency and handle updates correctly. Idempotency ensures that applying the same resource definition repeatedly produces the same result, avoiding unintended changes or side effects.

To achieve idempotency, consider performing checks to determine if the resource already exists or if any changes need to be made before taking action. This prevents unnecessary operations and ensures that updates are applied correctly without causing disruptions.

Additionally, handle updates carefully to minimize downtime and avoid unexpected behavior. Consider implementing mechanisms to detect changes and perform only the necessary updates, rather than recreating the entire resource.

**Implementing Error Handling and Rollbacks**

Error handling is an essential aspect of custom resource and resource type development. Proper error handling ensures that failures are gracefully handled, and AWS CloudFormation can recover from errors and roll back deployments if necessary.

Implement mechanisms to catch and handle exceptions, providing meaningful error messages and status updates to AWS CloudFormation. This enables better troubleshooting and error resolution during deployments.

Furthermore, consider implementing rollbacks in case of failures during resource creation or updates. Rollbacks allow you to revert to the previous state and ensure consistency and integrity in your infrastructure.

**Optimal Use of Permissions and IAM Roles**

When working with custom resources and resource types, it’s imperative to follow the principle of least privilege and ensure proper permission management. Grant only the necessary permissions to the Lambda functions or resource type handlers to interact with the required AWS services and third-party resources.

Utilize AWS Identity and Access Management (IAM) roles to assign appropriate permissions to the resources involved. IAM roles allow you to define fine-grained access control, ensuring that each component has only the permissions it needs to fulfill its role.

By adopting optimal permission management practices, you can enhance security, reduce the attack surface, and maintain a robust and controlled infrastructure.

**Real-World Use Cases For Custom Resources And Resource Types**

**Managing GitHub Repositories with AWS CloudFormation**

A common use case for custom resources in AWS CloudFormation is the management of GitHub repositories. By leveraging custom resources, you can create, update, and delete GitHub repositories directly from your AWS CloudFormation templates.

To achieve this, you would develop a custom resource that interacts with the GitHub API, allowing you to provision repositories, set access controls, and perform other necessary operations. By treating GitHub repositories as first-class resources in AWS CloudFormation, you can manage them alongside your other infrastructure resources seamlessly.

**Provisioning Third-Party Website Monitors**

Another real-world use case for custom resources is the provisioning of third-party website monitors. These monitors, typically provided by external vendors, offer services to track website availability, performance, and other metrics.

By developing a custom resource, you can integrate these third-party website monitors into your AWS CloudFormation templates. This allows you to provision and configure website monitors as part of your infrastructure deployments, ensuring comprehensive monitoring and observability.

**Looking Up Amazon Machine Images (AMIs) Dynamically**

In some scenarios, you may need to dynamically look up Amazon Machine Images (AMIs) just before creating EC2 instances in your AWS CloudFormation templates. This can be achieved by developing a custom resource that interacts with the AWS public API to retrieve the required AMI information based on specific criteria.

By leveraging this custom resource, you can automate the AMI lookup process, ensuring that the latest and appropriate AMIs are used in your deployments. This enhances flexibility and reduces manual intervention in the infrastructure provisioning process.

**Comparing Custom Resources And Resource Types**

**Schema Definition and Visibility**

One of the key differences between custom resources and resource types is the visibility and schema definition. Custom resources lack explicit schema declaration, making it challenging for AWS CloudFormation to validate templates and integrate with other services.

Resource types, on the other hand, provide a well-defined schema that explicitly declares the properties, inputs, and outputs of the resource. This schema enables better validation, visibility, and integration with AWS CloudFormation features and other AWS services.

Resource types offer a more structured and integrated approach to managing third-party resources, allowing for better validation, change management, and integration with AWS CloudFormation and other services.

**Language Support and Execution Location**

Custom resources can be developed using any language supported by AWS Lambda. This provides flexibility and allows developers to choose the language they are most comfortable with, such as Python, Node.js, or Java.

Resource types, however, currently support only Java, Go, and Python for handler code development. This limitation may impact the language choices for resource type development, depending on the development team’s preferences and expertise.

Another difference is the location of execution. Custom resources execute the logic in your AWS account, either through Lambda functions or SNS topics. In contrast, resource types execute the logic managed by AWS, with handlers executed in response to lifecycle events triggered by AWS CloudFormation.

**Development Workflow and Tooling**

The development workflow and tooling for custom resources and resource types differ to some extent. Custom resources offer a simpler and faster start with less upfront overhead. You can quickly get started by writing the necessary Lambda functions to handle the custom resource logic.

Resource types, on the other hand, require more upfront planning and adherence to a structured development workflow. The CloudFormation CLI provides tools and commands to generate the initial project structure, define the resource type specification, and write the necessary handler code.

While the resource type development process may require more effort and adherence to best practices, it offers benefits such as enhanced validation, visibility, and integration with AWS CloudFormation and other AWS services.


![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/hdcwsfkxegu9z81xrqc2.jpg)

**Overcoming Security Risks With Terraform And AWS CloudFormation**

**Protecting Against Infrastructure as Code (IaC) Drift**

Managing infrastructure as code (IaC) deployments in multi-region AWS environments can be challenging due to the risk of infrastructure drift. IaC drift occurs when the actual state of the deployed resources deviates from the expected state defined in the IaC templates.

To prevent IaC drift and mitigate security risks, it’s crucial to adopt strategies that ensure consistency and compliance across multiple AWS accounts and regions. One such strategy is to leverage Terraform, a widely used infrastructure provisioning tool.

By using Terraform in conjunction with AWS CloudFormation, you can enforce and maintain consistency in your infrastructure deployments. Terraform’s declarative language and state management capabilities enable you to define, provision, and track resources across multiple regions and accounts effectively.

**Securing Multi-Region Deployments with Terraform**

Multi-region deployments introduce additional security considerations, as each region may have different compliance requirements and security controls. To ensure the security of your multi-region deployments, it’s essential to implement best practices and adopt a defense-in-depth approach.

Terraform provides several features and capabilities to enhance the security of your multi-region deployments. These include support for AWS Identity and Access Management (IAM) roles, encryption of sensitive data, secure network configurations, and compliance with regulatory standards.

By leveraging Terraform’s security features and integrating it with AWS CloudFormation, you can achieve a robust and secure infrastructure deployment process in multi-region AWS environments.

**Conclusion**

In this comprehensive guide, we have explored the power of Python and AWS CloudFormation in managing third-party resources seamlessly. By leveraging custom resources, resource types, and the crhelper framework, you can extend the capabilities of AWS CloudFormation and integrate external services effectively.

We started by understanding the need for managing third-party resources within AWS CloudFormation and explored the limitations of native AWS resources. We then introduced custom resources, their role in AWS CloudFormation, and how to create them using Python and Lambda.

Next, we delved into resource types, their advantages over custom resources, and the development workflow using the CloudFormation CLI. We also discussed the crhelper framework, which simplifies custom resource development and ensures best practices.

To guide you through the process of managing third-party resources, we provided a step-by-step guide, covering the setup of the development environment, initialization of the custom resource provider, definition of the resource schema, implementation of the custom resource handlers, and testing and deployment of the custom resource.

We also highlighted best practices for custom resource and resource type development, emphasizing idempotency, error handling, rollbacks, and optimal permission management.

Furthermore, we showcased real-world use cases for custom resources and resource types, such as managing GitHub repositories, provisioning third-party website monitors, and dynamically looking up AMIs.

Finally, we compared custom resources and resource types, discussing their differences in schema definition, language support, execution location, development workflow, and tooling.

To address security risks in multi-region deployments, we explored how Terraform and AWS CloudFormation can be combined to protect against infrastructure as code drift and effectively secure multi-region deployments.

By leveraging the power of Python, AWS CloudFormation, and the associated tools and frameworks, you can unlock the full potential of infrastructure as code and manage third-party resources efficiently and securely.

**Glossary**

- AWS: Amazon Web Services
- AWS CLI: AWS Command Line Interface
- AWS CloudFormation: Amazon Web Services CloudFormation
- IAM: Identity and Access Management
- IaC: Infrastructure as Code
- AMI: Amazon Machine Image
- SaaS: Software-as-a-Service
- API: Application Programming Interface
- JSON: JavaScript Object Notation
- YAML: Yet Another Markup Language
- IDE: Integrated Development Environment
- EC2: Elastic Compute Cloud
- S3: Simple Storage Service
- Lambda: AWS Lambda
- SNS: Simple Notification Service
- CLI: Command Line Interface