The trend of building AWS Serverless applications using AWS Lambda is increasing at an ever-rapid pace. Common use cases for AWS Lambda include data processing, real-time file processing, and extract, transform, and load (ETL) for data processing, web backends, internet of things (IoT) backends, and mobile backends. Lambda natively supports languages such as Java, Go, PowerShell, Node.js, C#, Python, and Ruby. It also provides a Runtime API that allows you to use any additional programming languages to author your functions.

.NET framework occupies a significant footprint in the technology landscape of enterprises. Nowadays, enterprise customers are modernizing .NET framework applications to .NET Core using AWS Serverless (Lambda). In this journey, you break down a large monolith service into multiple smaller independent and autonomous microservices using.NET Core Lambda functions

When you have several microservices running in production, a change management strategy is key for business agility and time-to-market changes. The change management of .NET Core Lambda functions translates to how well you implement an automated CI/CD pipeline using AWS CodePipeline. In this post, you see two approaches for implementing CI/CD for .NET Core Lambda functions: creating a pipeline with either two or three stages.

In this approach, you define the pipeline in CodePipeline with two stages: AWS CodeCommit and AWS CodeBuild. CodeCommit is the fully-managed source control repository that stores the source code for .NET Core Lambda functions. It triggers CodeBuild when a new code change is published. CodeBuild defines a compute environment for the build process. It builds the .NET Core Lambda function and creates a deployment package (.zip). Finally, CodeBuild uses AWS extensions for Dotnet CLI to deploy the Lambda packages (.zip) to the Lambda environment. The following diagram illustrates this architecture.

CodePipeline with CodeBuild and CodeCommit stages.

In this approach, you define the pipeline with three stages: CodeCommit, CodeBuild, and AWS CodeDeploy.

CodeCommit stores the source code for .NET Core Lambda functions and triggers CodeBuild when a new code change is published. CodeBuild defines a compute environment for the build process and builds the .NET Core Lambda function. Then CodeBuild invokes the CodeDeploy stage. CodeDeploy uses AWS CloudFormation templates to deploy the Lambda function to the Lambda environment. The following diagram illustrates this architecture.

CodePipeline with CodeCommit, CodeBuild and CodeDeploy stages.

In this post, you learn how to implement an automated CI/CD pipeline using the first approach: CodePipeline with CodeCommit and CodeBuild stages. The CodeBuild stage in this approach implements the build and deploy functionalities. The high-level steps are as follows:

1. Create the CodeCommit repository.
2. Create a Lambda execution role.
3. Create a Lambda project with .NET Core CLI.
4. Change the Lambda project configuration.
5. Create a buildspec file.
6. Commit changes to the CodeCommit repository.
7. Create your CI/CD pipeline.
8. Complete and verify pipeline creation.

For the source code and buildspec file, see the GitHub repo.

Before you get started, you need the following prerequisites:

You first need a CodeCommit repository to store the Lambda project source code.

1. In the Repository settings section, for Repository name, enter a name for your repository.

2. Choose Create.

3. Initialize this repository with a markdown file (readme.md). You need this markdown file to create documentation about the repository.

4. Set up an AWS Identity and Access Management (IAM) credential to CodeCommit. Alternatively, you can set up SSH-based access. For instructions, see Setup for HTTPS users using Git credentials and Setup steps for SSH connections to AWS CodeCommit repositories on Linux, MacOS, or Unix. You need this to work with the CodeCommit repository from the development environment.

5. Clone the CodeCommit repository to a local folder.

Proceed to the next step to create an IAM role for Lambda execution.

Every Lambda function needs an IAM role for execution. Create an IAM role for Lambda execution with the appropriate IAM policy, if it doesn’t exist already. You’re now ready to create a Lambda function project using .NET Core Command Line Interface (CLI).