Building Serverless Applications with AWS and Terraform

In today's fast-paced development environment, serverless architecture has emerged as a powerful paradigm for building applications. By leveraging services like AWS Lambda, developers can focus on writing code without worrying about server management. In this article, we will explore how to build serverless applications using AWS and Terraform, a widely-used infrastructure as code (IaC) tool. Whether you are a seasoned developer or just getting started, this guide will provide you with actionable insights, code examples, and troubleshooting tips.

Understanding Serverless Architecture

What is Serverless?

Serverless computing allows developers to build and run applications without managing server infrastructure. Instead of provisioning servers, you rely on cloud providers to handle the backend resources. AWS Lambda is a leading serverless compute service that enables you to run code in response to events, such as HTTP requests or database changes.

Benefits of Serverless

• Cost-effective: You pay only for the compute time you use.
• Scalability: Automatically scales with the number of requests.
• Reduced operational overhead: Focus on writing code rather than managing servers.

Why Use Terraform?

Terraform is an open-source tool that allows you to define and provision infrastructure using a high-level configuration language. It is particularly beneficial for managing serverless applications for several reasons:

• Infrastructure as Code: Maintain your infrastructure in source control.
• Multi-provider support: Easily manage resources across different cloud providers.
• Modular and reusable: Create reusable modules for common infrastructure patterns.

Setting Up Your Environment

Before diving into coding, ensure you have the following tools installed:

1. AWS CLI: Command-line interface for AWS.
2. Terraform: Infrastructure as code tool.
3. Node.js: For writing serverless functions.
4. An AWS account: Set up with appropriate permissions.

Step 1: Configure AWS CLI

To configure your AWS credentials, run the following command:

aws configure

You will be prompted to enter your AWS Access Key, Secret Key, region, and output format.

Step 2: Install Terraform

Follow the official Terraform installation guide to install Terraform on your machine.

Building a Simple Serverless Application

Let's create a simple serverless application that responds to HTTP requests using AWS API Gateway and AWS Lambda, managed by Terraform.

Step 1: Create a Project Directory

mkdir serverless-app
cd serverless-app

Step 2: Write Your Lambda Function

Create a file named index.js and add the following JavaScript code:

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

Step 3: Define Terraform Configuration

Create a file named main.tf and add the following Terraform configuration:

provider "aws" {
  region = "us-east-1"
}

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

  # Specify the path to your Lambda deployment package
  filename      = "lambda.zip"

  source_code_hash = filebase64sha256("lambda.zip")

  role = aws_iam_role.lambda_exec.arn
}

resource "aws_iam_role" "lambda_exec" {
  name               = "lambda_exec_role"
  assume_role_policy = data.aws_iam_policy_document.lambda_assume_role_policy.json
}

data "aws_iam_policy_document" "lambda_assume_role_policy" {
  statement {
    actions = ["sts:AssumeRole"]
    principals {
      type        = "Service"
      identifiers = ["lambda.amazonaws.com"]
    }
  }
}

resource "aws_api_gateway_rest_api" "api" {
  name        = "serverless-api"
  description = "Serverless API with Lambda"
}

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" "get_hello" {
  rest_api_id   = aws_api_gateway_rest_api.api.id
  resource_id   = aws_api_gateway_resource.hello.id
  http_method   = "GET"
  authorization = "NONE"
}

resource "aws_api_gateway_integration" "hello_integration" {
  rest_api_id             = aws_api_gateway_rest_api.api.id
  resource_id             = aws_api_gateway_resource.hello.id
  http_method             = aws_api_gateway_method.get_hello.http_method
  integration_http_method = "POST"
  type                    = "AWS_PROXY"
  uri                     = aws_lambda_function.hello_function.invoke_arn
}

output "invoke_url" {
  value = "${aws_api_gateway_rest_api.api.invoke_url}/hello"
}

Step 4: Package Your Lambda Function

To package your Lambda function, run the following command:

zip lambda.zip index.js

Step 5: Deploy with Terraform

Initialize and apply your Terraform configuration:

terraform init
terraform apply

Review the resources to be created and type yes to proceed.

Step 6: Test Your Application

After the deployment is complete, you will see an output with the invoke_url. Use curl or your web browser to test the endpoint:

curl <invoke_url>

You should receive a response saying, "Hello, Serverless World!"

Troubleshooting Tips

• AWS Permissions: Ensure your AWS IAM role has the necessary permissions to execute Lambda and manage API Gateway.
• Lambda Timeout: If your function takes too long to execute, consider increasing the timeout setting in your Terraform configuration.
• Debugging: Use CloudWatch logs to debug your Lambda function. Add logging statements in your code to trace execution.

Conclusion

Building serverless applications with AWS and Terraform streamlines the development process and allows developers to focus on writing code. By following this guide, you can create a simple serverless application that responds to HTTP requests with AWS Lambda and API Gateway. As you gain experience, explore additional AWS services and advanced Terraform features to enhance your serverless architecture. Happy coding!