Building Secure Serverless Applications on Azure Using Terraform and API Management

In the rapidly evolving world of cloud computing, serverless architecture has gained immense popularity due to its scalability, cost-effectiveness, and reduced operational overhead. Azure, Microsoft's cloud platform, offers robust solutions for building serverless applications. When combined with Terraform for infrastructure as code and Azure API Management for security and governance, developers can create secure, efficient applications with ease. This article will walk you through the essential concepts, use cases, and actionable insights needed to build secure serverless applications on Azure using Terraform and API Management.

What is Serverless Architecture?

Serverless architecture allows developers to build and run applications without having to manage the underlying servers. Instead, the cloud provider takes care of server management, scaling, and maintenance. In Azure, serverless options include Azure Functions and Azure Logic Apps, which enable you to execute code in response to events without provisioning or managing servers.

Benefits of Serverless Architecture

• Cost Efficiency: Pay only for the resources you consume.
• Scalability: Automatically scale with demand.
• Reduced Maintenance: Focus on coding rather than managing infrastructure.

What is Terraform?

Terraform is an open-source Infrastructure as Code (IaC) tool that allows you to define and provision data center infrastructure using a high-level configuration language. It enables you to automate the deployment of your infrastructure, ensuring consistency and reducing human error.

Key Features of Terraform

• Declarative Configuration: Define your infrastructure using simple configuration files.
• Execution Plans: Preview changes before applying them.
• Resource Graph: Understand dependencies and resource relationships.

Setting Up Your Environment

Before we dive into building your serverless application, ensure you have the following prerequisites:

1. Azure Account: Sign up for an Azure account if you don’t have one.
2. Terraform Installed: Download and install Terraform from the official site.
3. Azure CLI: Install the Azure CLI to interact with Azure resources.

Step-by-Step Guide to Building a Secure Serverless Application

Step 1: Define Your Infrastructure with Terraform

Create a new directory for your Terraform configuration files. Inside this directory, create a file named main.tf.

provider "azurerm" {
  features {}
}

resource "azurerm_resource_group" "main" {
  name     = "my-serverless-rg"
  location = "East US"
}

resource "azurerm_storage_account" "storage" {
  name                     = "mystorageacct123"
  resource_group_name      = azurerm_resource_group.main.name
  location                 = azurerm_resource_group.main.location
  account_tier            = "Standard"
  account_replication_type = "LRS"
}

resource "azurerm_function_app" "function" {
  name                       = "myFunctionApp"
  location                   = azurerm_resource_group.main.location
  resource_group_name        = azurerm_resource_group.main.name
  storage_account_name       = azurerm_storage_account.storage.name
  os_type                    = "linux"
  version                    = "~3"
  identity {
    type = "SystemAssigned"
  }
}

Step 2: Deploy Your Infrastructure

Open your terminal, navigate to your Terraform directory, and run the following commands:

terraform init
terraform plan
terraform apply

This will initialize your Terraform environment and provision the specified resources in Azure.

Step 3: Create an Azure Function

Now, let’s create a simple Azure Function. You can use the Azure Functions Core Tools to create a new function:

func init MyFunctionProj --python
cd MyFunctionProj
func new --name HttpTrigger --template "HTTP trigger"

Edit the __init__.py file in the HttpTrigger directory to return a response:

import logging
import azure.functions as func

def main(req: func.HttpRequest) -> func.HttpResponse:
    logging.info('Python HTTP trigger function processed a request.')
    return func.HttpResponse("Hello, World!")

Step 4: Set Up Azure API Management

To secure your function, we will configure Azure API Management. This allows you to manage and secure your APIs effectively. Add the following to your main.tf:

resource "azurerm_api_management" "apim" {
  name                = "myAPIMService"
  resource_group_name = azurerm_resource_group.main.name
  location            = azurerm_resource_group.main.location
  publisher_name      = "My Company"
  publisher_email     = "admin@mycompany.com"
  sku {
    name     = "Developer"
    capacity = 1
  }
}

Step 5: Link Your Function to API Management

After provisioning API Management, link it to your Azure Function. You can do this through the Azure portal or with Azure CLI commands.

Here's a brief outline of what to do in the Azure portal:

1. Navigate to your API Management service.
2. Select “APIs” > “+ Add API” > “Function App”.
3. Choose your function app and select the function you created.

Step 6: Securing the API

To secure your API, you can apply policies in Azure API Management. For example, you can enforce subscription keys or OAuth 2.0 authentication.

Example Policy Configuration

Here’s an example of a policy that requires a subscription key:

<policies>
    <inbound>
        <check-header name="Ocp-Apim-Subscription-Key" failed-check-httpcode="401" />
    </inbound>
    <backend>
        <forward-request />
    </backend>
    <outbound>
        <set-header name="X-My-Custom-Header" exists-action="override">
            <value>My Value</value>
        </set-header>
    </outbound>
</policies>

Conclusion

Building secure serverless applications on Azure using Terraform and API Management not only enhances security but also streamlines development. By leveraging Infrastructure as Code with Terraform, you can manage your resources efficiently. Coupled with Azure’s API Management, you can secure your applications and manage APIs effectively.

With the provided step-by-step guide and code snippets, you are now equipped to create your own serverless applications. Dive in, experiment with the features, and enhance your cloud skills while building scalable and secure applications!