Building Serverless Applications on AWS with Terraform and Docker

In the ever-evolving world of cloud computing, serverless architectures have gained tremendous popularity. They enable developers to focus on writing code without the hassle of managing infrastructure. By combining serverless computing with Infrastructure as Code (IaC) tools like Terraform and container technology like Docker, you can create scalable, resilient applications. This article will walk you through the process of building serverless applications on AWS using Terraform and Docker, providing you with actionable insights, code examples, and troubleshooting tips.

What Are Serverless Applications?

Serverless applications allow developers to build and run applications without having to manage servers. In this model, the cloud provider automatically provisions, scales, and manages the infrastructure required to run your code. AWS Lambda is a prime example of a serverless compute service that lets you run your code in response to events such as HTTP requests, file uploads, or database changes.

Key Benefits of Serverless Architecture

• Cost-Effective: Pay only for the compute time you consume.
• Scalability: Automatically scales with traffic spikes.
• Reduced Operational Overhead: Focus on writing code rather than managing infrastructure.

Why Use Terraform and Docker?

Terraform

Terraform is an open-source IaC tool that allows you to define and provision your infrastructure using code. It provides a consistent CLI workflow to manage your cloud resources. Using Terraform for your serverless applications offers several advantages:

• Version Control: Infrastructure can be versioned alongside your application code.
• Reusability: Easily replicate environments for development, testing, and production.
• Multi-Cloud Support: Deploy across various cloud providers with minimal changes.

Docker

Docker allows you to package applications and their dependencies into standardized units called containers. When combined with serverless applications, Docker provides a consistent environment for development, testing, and production. This eliminates the "it works on my machine" problem.

Use Case: Building a Serverless Web Application

Let’s build a simple serverless web application that responds to HTTP requests. We will use AWS Lambda for the backend logic, API Gateway for handling HTTP requests, Terraform for infrastructure provisioning, and Docker for containerization.

Prerequisites

Before you start, ensure you have the following installed:

• AWS CLI
• Terraform
• Docker

Step 1: Setting Up Your Docker Environment

Create a simple Node.js application that will run in a Docker container. First, create a new directory for your project:

mkdir serverless-app
cd serverless-app

Create a Dockerfile in the project directory:

# Dockerfile
FROM node:14

WORKDIR /usr/src/app

COPY package*.json ./
RUN npm install

COPY . .

CMD [ "node", "index.js" ]

Next, create a simple index.js file:

// index.js
const http = require('http');

const requestHandler = (req, res) => {
  res.end('Hello, Serverless World!');
};

const server = http.createServer(requestHandler);

const PORT = process.env.PORT || 3000;
server.listen(PORT, () => {
  console.log(`Server is running on port ${PORT}`);
});

Create a package.json file:

{
  "name": "serverless-app",
  "version": "1.0.0",
  "main": "index.js",
  "scripts": {
    "start": "node index.js"
  },
  "dependencies": {}
}

Step 2: Building and Running Your Docker Container

Build your Docker image:

docker build -t serverless-app .

Run your Docker container:

docker run -p 3000:3000 serverless-app

Navigate to http://localhost:3000 in your browser, and you should see "Hello, Serverless World!".

Step 3: Defining Infrastructure with Terraform

Next, we will define our AWS infrastructure using Terraform. Create a main.tf file in your project directory:

# main.tf
provider "aws" {
  region = "us-east-1"
}

resource "aws_lambda_function" "serverless_app" {
  function_name = "ServerlessApp"
  handler       = "index.handler"
  runtime       = "nodejs14.x"

  s3_bucket = aws_s3_bucket.lambda_bucket.bucket
  s3_key    = aws_s3_bucket_object.lambda_object.key

  source_code_hash = filebase64sha256("path/to/your/docker/image")
}

resource "aws_api_gateway_rest_api" "api" {
  name        = "ServerlessAPI"
  description = "API for Serverless Application"
}

resource "aws_api_gateway_resource" "hello" {
  rest_api_id = aws_api_gateway_rest_api.api.id
  parent_id   = aws_api_gateway_rest_api.api.root_resource_id
  path_part   = "hello"
}

resource "aws_api_gateway_method" "hello_method" {
  rest_api_id   = aws_api_gateway_rest_api.api.id
  resource_id   = aws_api_gateway_resource.hello.id
  http_method   = "GET"
  authorization = "NONE"

  integration {
    http_method = "POST"
    type        = "aws_proxy"
    uri         = aws_lambda_function.serverless_app.invoke_arn
  }
}

Step 4: Deploying with Terraform

Initialize Terraform:

terraform init

Plan your deployment:

terraform plan

Deploy your infrastructure:

terraform apply

Step 5: Testing Your API

Once your API Gateway is created, you’ll receive an endpoint URL in the output. Use Postman or curl to test your serverless application:

curl https://your-api-id.execute-api.us-east-1.amazonaws.com/prod/hello

You should receive a response: "Hello, Serverless World!".

Troubleshooting Tips

• Lambda Timeout: Ensure your function’s timeout setting is sufficient for your application’s needs.
• API Gateway Errors: Check the integration settings in API Gateway and ensure that the Lambda function has the correct permissions.
• Deployment Issues: Review Terraform logs for any errors during the apply process.

Conclusion

Building serverless applications on AWS using Terraform and Docker can significantly streamline your development process. By leveraging the power of containers and IaC, you can create scalable, cost-effective solutions while minimizing operational overhead. With this guide, you now have the foundational knowledge to start building your serverless applications. Happy coding!