HTTP Triggers in Azure Functions

An HTTP trigger in Azure Functions allows you to invoke your function via an HTTP request. This means you can trigger your function by sending an HTTP request to a specific URL, making it ideal for building APIs, and webhooks, and handling HTTP-based workflows.

In our system, we frequently use time trigger Azure Functions to send notifications to customers via email. However, we encounter occasional failures due to exceptions, timeouts, or other unforeseen issues. As a result, some emails do not get sent at the scheduled time, leading to delays in customer notifications. To address these failures, in this case, we are manually resending the emails from a local machine or updating the execution time of the function. These methods are not only time-consuming but also inefficient. We need a more robust and automated solution to handle these failures and ensure timely email delivery. This is where HTTP Triggers in Azure Functions can provide a significant advantage.

let’s explore some additional information about the HTTP trigger function.

Use Cases for HTTP Triggers:

Webhook and Event Handling: Respond to events from external services like GitHub or payment gateways using HTTP triggers to process incoming data or trigger actions.

Integration with External Services: Integrate seamlessly with external systems by invoking your functions via HTTP requests. This enables scenarios like processing external data or triggering actions based on external events.

Custom Web Endpoints: Create custom endpoints for specific functionalities in your application, such as processing user input or triggering background tasks.

Key Attributes:

AuthLevel: Defines the authorization level (e.g., Anonymous, Function) for accessing the function endpoint.\

Methods: Specifies the supported HTTP methods (GET, POST, PUT, etc.) for the trigger.

Route: Defines the specific URL path for the endpoint.

Request Body: The request body is expected to contain data in the format that can be deserialized into an HttpTriggerRequest

Security Key: requires a security token or key in the request headers to authenticate and authorize the request.

Example: HTTP-Triggered Azure Function in C# .NET Core

In case of a failure in our TimerTrigger function, which is responsible for sending daily performance email reports, the HTTP trigger function RunDailyPerformanceEmailHttpTriggerFunction comes into play. This HTTP trigger function is specifically designed to handle POST requests, and it’s integrated into our system to send reports for a particular date when the TimerTrigger function fails.

[AuthorizeFunction]
        [FunctionName("RunDailyPerformanceEmailHttpTriggerFunction")]
        public async Task<IActionResult> RunDailyPerformanceEmailHttpTriggerAsync([HttpTrigger(AuthorizationLevel.Anonymous, "post", Route = null)] HttpRequestMessage req, ILogger logger)
        {               
               
              HttpTriggerRequest httpTriggerRequest = JsonConvert.DeserializeObject<HttpTriggerRequest>(await req.Content.ReadAsStringAsync());

              var isSent = await _dailyPerformanceService.SendDailyBookingReportAsync(Convert.ToDateTime(httpTriggerRequest.EmailDate));
                    
              logger.LogWarning($"RunDailyPerformanceEmailHttpTrigger completed at: {DateTime.Now.ToString(DATETIME_FORMAT)}");               

              return new OkResult();

        }

Below are the steps to trigger the functions through Http trigger, when configured:

1. Get URL for function from Azure portal
2. All functions are restricted to POST request
3. You need to send function token to execute request as “x-function-key” header parameter.
4. You can get function token and URL from Azure portal.
5. You can use any client to trigger functions like Postman.

How to get the function Http trigger endpoint and key

How to call the Http trigger endpoint through Postman:

Conclusion:

HTTP triggers in Azure Functions offer a versatile and powerful tool for building responsive APIs, handling webhooks, and integrating with external services. Their ability to serve as fail-safes in time-based automation scenarios adds an extra layer of reliability to your workflows. By understanding their use cases, key attributes, and integration steps, you can leverage HTTP triggers effectively to create efficient and scalable solutions in your Azure environment.