Guide to Deploying Serverless Applications on AWS with Terraform

In today's fast-paced digital landscape, businesses are increasingly turning to serverless architectures to develop and deploy applications. Serverless computing allows developers to focus on writing code without worrying about the underlying infrastructure, making it a popular choice for modern applications. When combined with Infrastructure as Code (IaC) tools like Terraform, deploying serverless applications on AWS becomes a streamlined, efficient process. This article will guide you through the steps to deploy serverless applications on AWS using Terraform, complete with code examples, use cases, and troubleshooting tips.

What is Serverless Computing?

Before diving into the deployment process, let's clarify what serverless computing entails. Serverless computing is a cloud-computing execution model where the cloud provider dynamically manages the allocation of machine resources. The key benefits include:

• Cost Savings: You only pay for what you use, eliminating the need to provision and manage servers.
• Scalability: Automatically scales your applications in response to incoming requests.
• Reduced Operational Overhead: Developers can focus on writing code rather than managing infrastructure.

AWS Lambda is one of the most popular serverless computing services, allowing you to run code in response to events such as HTTP requests, database changes, or file uploads.

Why Use Terraform for Serverless Deployments?

Terraform, developed by HashiCorp, is an open-source IaC tool that allows you to define and provision data center infrastructure using a high-level configuration language. It integrates seamlessly with AWS services, making it an ideal choice for deploying serverless applications. Here are some key advantages:

• Version Control: Manage your infrastructure configurations as code, enabling version control and collaboration.
• Modularity: Create reusable modules for your serverless applications, promoting consistency and reducing duplication.
• Automation: Automate the deployment process, minimizing manual errors and saving time.

Step-by-Step Guide to Deploying a Serverless Application on AWS with Terraform

In this section, we will create a simple serverless application that responds to HTTP requests using AWS Lambda and API Gateway. We'll structure our project using Terraform.

Prerequisites

Before you begin, ensure you have the following:

• An AWS account
• Terraform installed on your local machine
• AWS CLI configured with your credentials

Step 1: Set Up Your Project Directory

Create a new directory for your project:

mkdir my-serverless-app
cd my-serverless-app

Step 2: Initialize a Terraform Configuration

Create a file named main.tf in your project directory. This file will contain the Terraform configuration for our serverless application.

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

resource "aws_lambda_function" "hello_world" {
  function_name = "HelloWorldFunction"

  handler = "hello.handler"
  runtime = "nodejs14.x"

  s3_bucket = aws_s3_bucket.lambda_bucket.bucket
  s3_key    = "lambda_function.zip"

  environment {
    VAR1 = "value1"
  }

  role = aws_iam_role.lambda_exec.arn
}

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

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

resource "aws_s3_bucket" "lambda_bucket" {
  bucket = "my-serverless-app-bucket"
}

resource "aws_api_gateway_rest_api" "api" {
  name = "HelloWorldAPI"
}

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" {
  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" "lambda" {
  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.http_method
  integration_http_method = "POST"
  type                    = "AWS_PROXY"
  uri                     = aws_lambda_function.hello_world.invoke_arn
}

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

  # Specify the source ARN for the API Gateway
  source_arn = "${aws_api_gateway_rest_api.api.execution_arn}/*/*"
}

Step 3: Create the Lambda Function Code

Create a directory named lambda and add a file called hello.js:

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

Step 4: Package and Upload Your Lambda Function

Zip your Lambda function code:

cd lambda
zip ../lambda_function.zip hello.js
cd ..

Step 5: Deploy Your Application

Now that we have our configuration set up, it’s time to deploy our serverless application.

1. Initialize Terraform:

bash terraform init

1. Plan the Deployment:

bash terraform plan

1. Apply the Configuration:

bash terraform apply

Confirm the action by typing yes when prompted.

Step 6: Test Your API

After successfully deploying your application, you can test it by accessing the API Gateway URL. You can find the URL in the AWS console under the API Gateway section or by adding an output to your main.tf file.

Troubleshooting Tips

• Lambda Timeout Errors: If your function times out, consider increasing the timeout setting in the Lambda configuration.
• Permissions Issues: Ensure that the IAM role associated with your Lambda function has the necessary permissions.
• API Gateway Errors: Check API Gateway logs for any errors during invocation.

Conclusion

Deploying serverless applications on AWS using Terraform simplifies the deployment process, enhances collaboration, and reduces operational overhead. With the steps outlined in this guide, you can create a robust serverless application and leverage the power of AWS services. As you continue to build and optimize your applications, consider modularizing your Terraform configurations for better maintainability and scalability. Embrace the serverless revolution and enjoy the freedom to innovate without the burden of infrastructure management!