Golang webservice with Elastic Container Service, Application Load Balancer, and DynamoDB

Introduction

This Golang app creates a basic web service for adding and retrieving posts. It's leverages Elastic Container Service (ECS) and Application Load Balancer (ALB) for containerized app deployment and scaling. DynamoDB is used to store posts. The app is deployable on LocalStack and AWS seamlessly using Cloud Development Kit (CDK). To test, we'll show how to use LocalStack to deploy infrastructure on your developer machine and CI environment.

Architecture

The following diagram shows the architecture that this sample application builds and deploys:

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We are using the following AWS services and their features to build our infrastructure:

• ECS as a container orchestration service to deploy and manage containers using Fargate.
• DynamoDB as a key-value NoSQL database to store and retrieve posts.
• Elastic Load Balancing to distribute incoming traffic across multiple targets on ECS.

Prerequisites

• LocalStack Pro with the localstack CLI.
• Cloud Development Kit (CDK) installed with the cdklocal wrapper.
• Node.js with the yarn package manager.
• curl or a similar tool to test the application.

Start LocalStack Pro with the LOCALSTACK_AUTH_TOKEN pre-configured:

export LOCALSTACK_AUTH_TOKEN=<your-auth-token>
localstack start

If you prefer running LocalStack in detached mode, you can add the -d flag to the localstack start command, and use Docker Desktop to view the logs.

Instructions

Install the dependencies

Install the Node.js dependencies by running the following command in the cdk directory:

yarn install

Deploy the application

To create the AWS infrastructure locally, you can use CDK and our cdklocal wrapper.

cdklocal bootstrap
cdklocal deploy --all

This will deploy the ddblocal-fargate-stack stack, which includes the ECS service, the Application Load Balancer, and the DynamoDB table. You will see the output of the stack, including the URL of the load balancer.

✅  ddblocal-fargate-stack

✨  Deployment time: 30.16s

Outputs:
ddblocal-fargate-stack.MyFargateServiceLoadBalancerDNS704F6391 = lb-9f06ca8a.elb.localhost.localstack.cloud
ddblocal-fargate-stack.MyFargateServiceServiceURL4CF8398A = http://lb-9f06ca8a.elb.localhost.localstack.cloud
Stack ARN:
arn:aws:cloudformation:us-east-1:000000000000:stack/ddblocal-fargate-stack/483afbca

✨  Total time: 32.92s

Copy the MyFargateServiceServiceURL output and use it to test the application.

Testing the application

Run the following command to add a post to the database:

curl -X POST https://lb-bee07cad.elb.localhost.localstack.cloud/post \
     -H "Content-Type: application/json" \
     -d '{
        "id": "1",
        "title": "my post #1",
        "content": "here is the post content",
        "status": "posted"
     }'

Replace lb-bee07cad.elb.localhost.localstack.cloud with the URL of your load balancer. Run the following command to retrieve the post from the database:

curl -X GET https://lb-bee07cad.elb.localhost.localstack.cloud/post/1

You can additionally navigate to the LocalStack Web Application and the DynamoDB Resource Browser.

Click on the blog-post-table* table to view the items. You can view the items by switching to scan, selecting the index, and clicking Submit. You will see the following:

Run the unit tests

You can run DynamoDB unit tests for the application which creates a table, adds a post, and retrieves the post. Install the Go dependencies by running the following command in the root directory:

go get -t dynamodb-local-test/pkg/service

Run the tests by running the following command:

docker-compose up --detach
pushd pkg/service && go test
popd
docker-compose down

GitHub Action

This application sample hosts an example GitHub Action workflow that starts up LocalStack, builds the Lambda functions, and deploys the infrastructure on the runner. You can find the workflow in the .github/workflows/main.yml file. To run the workflow, you can fork this repository and push a commit to the main branch.

Users can adapt this example workflow to run in their own CI environment. LocalStack supports various CI environments, including GitHub Actions, CircleCI, Jenkins, Travis CI, and more. You can find more information about the CI integration in the LocalStack documentation.

Contributing

We appreciate your interest in contributing to our project and are always looking for new ways to improve the developer experience. We welcome feedback, bug reports, and even feature ideas from the community. Refer to the contributing guide for more details on how to get started.