Building Serverless Applications on AWS with Docker and Terraform

In the rapidly evolving world of cloud computing, serverless architecture has emerged as a game-changer. It allows developers to focus on writing code without worrying about the underlying infrastructure. When combined with Docker and Terraform, building serverless applications on AWS becomes even more efficient and manageable. This article will guide you through the process of creating serverless applications using these powerful tools, providing actionable insights, code examples, and troubleshooting tips.

What is Serverless Architecture?

Serverless architecture refers to a cloud computing model where the cloud provider dynamically manages the allocation of machine resources. In this model, developers can run their applications without having to provision servers. AWS Lambda is a prime example of a serverless service, allowing you to execute code in response to events without managing servers.

Key Benefits of Serverless Architecture:

• Cost Efficiency: Pay only for the compute time used.
• Automatic Scaling: Automatically scales the application based on demand.
• Reduced Operational Overhead: Focus on code rather than infrastructure management.

Why Use Docker with Serverless Applications?

Docker is a platform that automates the deployment of applications inside lightweight containers. When used with serverless applications, Docker provides the following advantages:

• Consistency Across Environments: Docker containers ensure that your application runs the same way in development, testing, and production.
• Simplified Dependency Management: Package your application and its dependencies together, eliminating compatibility issues.
• Isolation: Each Docker container runs independently, enhancing security and stability.

Terraform: Infrastructure as Code

Terraform is an open-source tool that allows you to define and provision cloud infrastructure using a simple configuration language. With Terraform, you can manage AWS resources easily and reproducibly. Here’s why Terraform is a great choice for serverless applications:

• Version Control: Keep track of infrastructure changes over time.
• Automation: Automate the deployment of cloud resources, reducing manual errors.
• Multi-Cloud Support: Manage resources across different cloud providers.

Getting Started: Prerequisites

Before diving into building a serverless application, ensure you have the following installed:

1. AWS CLI: Command-line tool for managing AWS services.
2. Docker: To build and run your containerized applications.
3. Terraform: For infrastructure provisioning.
4. An AWS account with permissions to create Lambda functions, API Gateway, and other necessary resources.

Step-by-Step Guide to Building a Serverless Application

Step 1: Create a Simple Node.js Application

Let’s start by creating a simple Node.js application that responds to HTTP requests.

// index.js
exports.handler = async (event) => {
    const response = {
        statusCode: 200,
        body: JSON.stringify('Hello from Serverless Application!'),
    };
    return response;
};

Step 2: Dockerize the Application

Next, create a Dockerfile to package your application into a Docker container.

# Dockerfile
FROM node:14

WORKDIR /usr/src/app
COPY package*.json ./
RUN npm install
COPY . .

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

Step 3: Build and Test the Docker Image

Run the following commands to build and test your Docker image locally.

docker build -t my-serverless-app .
docker run -p 9000:8080 my-serverless-app

You can test the application by navigating to http://localhost:9000 in your web browser.

Step 4: Define Infrastructure with Terraform

Next, create a main.tf file to define the necessary AWS resources.

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

resource "aws_lambda_function" "my_lambda" {
  function_name = "myServerlessApp"
  handler = "index.handler"
  runtime = "nodejs14.x"
  role = aws_iam_role.lambda_exec.arn

  filename         = "my-serverless-app.zip"
  source_code_hash = filebase64sha256("my-serverless-app.zip")
}

resource "aws_iam_role" "lambda_exec" {
  name = "lambda_exec"
  assume_role_policy = jsonencode({
    Version = "2012-10-17"
    Statement = [{
      Action = "sts:AssumeRole"
      Principal = {
        Service = "lambda.amazonaws.com"
      }
      Effect = "Allow"
      Sid = ""
    }]
  })
}

Step 5: Package the Application for Lambda

Zip your application for deployment:

zip my-serverless-app.zip index.js package.json

Step 6: Deploy with Terraform

Run the following commands to deploy your infrastructure:

terraform init
terraform apply

Review the changes and type yes to confirm the deployment. Terraform will provision the Lambda function and IAM role.

Step 7: Set Up API Gateway

To expose your Lambda function via HTTP, you can create an API Gateway:

resource "aws_api_gateway_rest_api" "api" {
  name        = "my_api"
  description = "My Serverless API"
}

resource "aws_api_gateway_resource" "resource" {
  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" "method" {
  rest_api_id   = aws_api_gateway_rest_api.api.id
  resource_id   = aws_api_gateway_resource.resource.id
  http_method   = "GET"
  authorization = "NONE"
}

resource "aws_api_gateway_integration" "integration" {
  rest_api_id = aws_api_gateway_rest_api.api.id
  resource_id = aws_api_gateway_resource.resource.id
  http_method = aws_api_gateway_method.method.http_method

  integration_http_method = "POST"
  type                    = "AWS_PROXY"
  uri                     = aws_lambda_function.my_lambda.invoke_arn
}

Step 8: Update and Apply Changes

Run terraform apply again to deploy the API Gateway. You can find the endpoint URL in the AWS console under API Gateway, and calling this URL will trigger your Lambda function.

Troubleshooting Tips

• Logs and Monitoring: Use CloudWatch to monitor your Lambda functions and troubleshoot issues.
• IAM Permissions: Ensure your IAM roles have the necessary permissions for Lambda execution and API Gateway.
• Container Size: Keep your Docker images lightweight to improve cold start times.

Conclusion

Building serverless applications on AWS with Docker and Terraform empowers developers to create scalable and efficient applications without the burden of managing infrastructure. By leveraging these tools, you can streamline your development process, reduce costs, and focus on delivering value to your users. Start your serverless journey today and unlock the full potential of cloud computing!