Creating Azure Functions

This guide provides a comprehensive walkthrough on how to create and deploy Azure Functions, a serverless compute service that enables you to run code on demand without managing infrastructure. Azure Functions can be triggered by a wide range of Azure services and external events.

We'll cover creating functions using different development environments and common triggers.

Prerequisites

Before you begin, ensure you have the following:

• An Azure subscription.
• The Azure Functions Core Tools installed.
• A code editor or IDE, such as Visual Studio Code with the Azure Functions extension.
• Node.js (for JavaScript/TypeScript functions) or .NET SDK (for C# functions), depending on your chosen language.

Creating a Function from the Azure Portal

The easiest way to get started is by creating a function directly in the Azure portal.

Steps:

1. Navigate to the Azure portal and sign in.
2. Click on Create a resource.
3. Search for Function App and select it.
4. Click Create.
5. Fill in the required details:
   • Subscription: Choose your Azure subscription.
   • Resource group: Create a new one or select an existing one.
   • Function App name: A globally unique name for your function app.
   • Runtime stack: Select your preferred language (e.g., .NET, Node.js, Python).
   • Version: Select the runtime version.
   • Region: Choose the Azure region closest to you or your users.
6. Configure hosting options (Storage account, Operating System, Plan type). For simplicity, the Consumption plan is often a good starting point.
7. Click Review + create, then Create.

Once the Function App is deployed, you can navigate to it, click on Functions, then Create to add a new function, selecting a template and trigger.

Creating a Function Locally with Azure Functions Core Tools

Developing locally provides a faster development cycle and better debugging capabilities.

Steps:

1. Open your terminal or command prompt.
2. Navigate to your desired project directory.
3. Initialize a new Functions project:

   func init MyFunctionProject --worker-runtime 

   Replace <runtime> with your chosen runtime (e.g., dotnet, node, python).

4. Create a new function within the project:

   cd MyFunctionProject
   func new --name MyHttpTrigger --template "HTTP trigger" --authlevel "anonymous"

   This command creates a new HTTP-triggered function named MyHttpTrigger with anonymous authentication.

5. Run the local development server:

   func start

Common Triggers

Azure Functions can be triggered by various events:

HTTP Trigger

This is one of the most common triggers, allowing your function to be invoked via an HTTP request. It's ideal for building APIs and webhooks.

Example (JavaScript):

module.exports = async function (context, req) {
    context.log('JavaScript HTTP trigger function processed a request.');

    const name = (req.query.name || (req.body && req.body.name));
    const responseMessage = name
        ? 'Hello, ' + name + '!'
        : 'This HTTP triggered function executed successfully. Pass a name in the query string or in the request body for a personalized response.';

    context.res = {
        status: 200,
        body: responseMessage
    };
};

Timer Trigger

The Timer trigger allows you to execute functions on a schedule, defined using a CRON expression.

Example (CRON expression for every 5 minutes):

*/5 * * * *

This is useful for periodic tasks like data cleanup or scheduled reports.

Blob Trigger

This trigger executes your function when a new or updated blob is detected in an Azure Storage blob container.

Example usage:

Process uploaded images, perform data transformations on new files, or trigger notifications.

Deploying Your Local Functions

After developing and testing locally, you can deploy your function app to Azure:

1. Ensure you are logged into Azure via the CLI: az login
2. Deploy your project:

   func azure functionapp publish 

Monitoring and Management

Once deployed, you can monitor your functions using Azure Application Insights. This provides insights into execution times, errors, and invocation logs.

You can also manage function settings, view logs, and test functions directly from the Azure portal.