Developing Serverless Applications on AWS Lambda Using Terraform

In today’s fast-paced digital landscape, businesses are increasingly turning to serverless architectures to streamline their operations and reduce costs. AWS Lambda is a pivotal service in this realm, allowing developers to run code without provisioning or managing servers. Coupling AWS Lambda with Terraform, an open-source infrastructure as code (IaC) tool, empowers developers to define, deploy, and manage serverless applications efficiently. In this article, we will delve into the process of developing serverless applications on AWS Lambda using Terraform, providing you with actionable insights, detailed code examples, and step-by-step instructions.

What is AWS Lambda?

AWS Lambda is a compute service that lets you run code in response to events without the need to provision or manage servers. It automatically scales your applications by running code on demand, which means you only pay for the compute time you consume. This event-driven architecture is ideal for various use cases, including:

• Data processing: Automating data workflows and processing streams.
• Web applications: Serving APIs and handling backend logic.
• Automation: Triggering tasks based on events in AWS services.

What is Terraform?

Terraform is an open-source tool created by HashiCorp that allows you to define your cloud infrastructure using a declarative configuration language known as HashiCorp Configuration Language (HCL). With Terraform, you can manage AWS resources, including AWS Lambda functions, efficiently and reproducibly. By using IaC, you can maintain version control, automate deployments, and simplify infrastructure management.

Prerequisites

Before diving into the development of serverless applications with AWS Lambda and Terraform, ensure you have:

• An AWS account
• Terraform installed on your local machine
• Basic knowledge of AWS services and Terraform syntax

Setting Up Your Environment

To begin, create a new directory for your project and initialize it with Terraform:

mkdir my-serverless-app
cd my-serverless-app
terraform init

This command initializes your Terraform project and downloads the necessary provider plugins.

Creating a Simple AWS Lambda Function

Let’s create a simple AWS Lambda function that responds to HTTP requests via API Gateway. Follow these steps:

Step 1: Write the Lambda Function

Create a new file named lambda_function.py with the following code:

def lambda_handler(event, context):
    return {
        'statusCode': 200,
        'body': 'Hello from AWS Lambda!'
    }

Step 2: Define Your Terraform Configuration

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

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

resource "aws_lambda_function" "my_lambda" {
  function_name = "my_lambda_function"
  handler       = "lambda_function.lambda_handler"
  runtime       = "python3.8"
  role          = aws_iam_role.lambda_exec.arn

  # Package the Lambda function code as a zip
  filename      = "lambda_function.zip"

  source_code_hash = filebase64sha256("lambda_function.zip")
}

resource "aws_iam_role" "lambda_exec" {
  name = "lambda_exec_role"

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

resource "aws_iam_role_policy_attachment" "lambda_logs" {
  policy_arn = "arn:aws:iam::aws:policy/service-role/AWSLambdaBasicExecutionRole"
  role       = aws_iam_role.lambda_exec.name
}

Step 3: Package Your Lambda Function

Before deploying, package your Lambda function into a zip file:

zip lambda_function.zip lambda_function.py

Step 4: Deploy Your Application

Use the following Terraform commands to deploy your serverless application:

terraform apply

Terraform will prompt you to confirm the changes. Type yes to proceed. Once the deployment is complete, Terraform will output the details of your Lambda function.

Creating an API Gateway

To expose your Lambda function via HTTP, you’ll need to set up an API Gateway. Add the following resources to your main.tf:

resource "aws_api_gateway_rest_api" "my_api" {
  name        = "my_api"
  description = "API for my Lambda function"
}

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

resource "aws_api_gateway_method" "my_method" {
  rest_api_id   = aws_api_gateway_rest_api.my_api.id
  resource_id   = aws_api_gateway_resource.my_resource.id
  http_method   = "GET"
  authorization = "NONE"
}

resource "aws_api_gateway_integration" "my_integration" {
  rest_api_id             = aws_api_gateway_rest_api.my_api.id
  resource_id             = aws_api_gateway_resource.my_resource.id
  http_method             = aws_api_gateway_method.my_method.http_method
  integration_http_method = "POST"
  type                    = "AWS_PROXY"
  uri                     = aws_lambda_function.my_lambda.invoke_arn
}

resource "aws_lambda_permission" "allow_api_gateway" {
  statement_id  = "AllowAPIGatewayInvoke"
  action        = "lambda:InvokeFunction"
  function_name = aws_lambda_function.my_lambda.function_name
  principal     = "apigateway.amazonaws.com"

  # Specify the source ARN to limit permissions
  source_arn = "${aws_api_gateway_rest_api.my_api.execution_arn}/*"
}

Step 5: Redeploy Your Application

After updating your main.tf, run the following command to apply the changes:

terraform apply

Step 6: Test Your API

Once deployed, you can test your API using the endpoint provided in the output. Use curl or a browser to hit the endpoint:

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

You should see a response:

Hello from AWS Lambda!

Troubleshooting Common Issues

While working with AWS Lambda and Terraform, you may encounter some common issues:

• Permissions errors: Ensure your IAM roles and policies are set up correctly. Check the AWS Management Console for errors in the Lambda function logs.
• Incorrect resource configurations: Review your Terraform configuration files for typos or misconfigurations.
• Deployment failures: If the deployment fails, run terraform plan to identify issues before applying changes.

Conclusion

Developing serverless applications on AWS Lambda using Terraform allows you to harness the power of cloud computing without server management overhead. By following the steps outlined in this article, you can efficiently build, deploy, and manage serverless applications, unlocking a plethora of possibilities for your projects. Embrace the serverless paradigm and start your journey toward scalable, cost-effective application development today!