Azure Documentation

Azure Functions Event Grid Trigger

The Azure Functions Event Grid trigger allows you to create serverless functions that react to events published by Azure Event Grid. Event Grid is a fully managed event routing service that enables you to easily build applications with an event-driven architecture. This trigger simplifies the process of integrating your functions with Event Grid, allowing you to respond to a wide range of events from Azure services and custom sources.

Prerequisites

• An Azure subscription. If you don't have one, create a free account before you begin.
• An Azure Function App. If you don't have one, see the Azure Functions quickstart to create one.
• An Azure Event Grid topic or domain. You can create one from the Azure portal.

Create the function

You can create an Event Grid triggered function using various development tools. Here's an example using Visual Studio Code with the Azure Functions extension:

1. Open your Function App project in Visual Studio Code.
2. Create a new function.
3. Select the "Azure Event Grid Trigger" template.
4. Name your function (e.g., `EventGridHandler`).
5. The template will generate a function file (e.g., `EventGridHandler.cs` or `EventGridHandler/index.js`) and a `function.json` file.

Example (C#):

using Microsoft.Azure.WebJobs;
using Microsoft.Azure.EventGrid.Models;
using Microsoft.Extensions.Logging;

public static class EventGridHandler
{
    [FunctionName("EventGridHandler")]
    public static void Run([EventGridTrigger] EventGridEvent eventGridEvent, ILogger log)
    {
        log.LogInformation($"Event Type: {eventGridEvent.EventType}");
        log.LogInformation($"Subject: {eventGridEvent.Subject}");
        log.LogInformation($"Event Time: {eventGridEvent.EventTime}");
        log.LogInformation($"Data: {eventGridEvent.Data.ToString()}");

        // Your custom logic to handle the event
        // For example, process the data, send notifications, update a database, etc.
    }
}
                

Example (Node.js):

module.exports = async function (context, eventGridEvent) {
    context.log('JavaScript Event Grid trigger function processed an event.');
    context.log(`Event Type: ${eventGridEvent.eventType}`);
    context.log(`Subject: ${eventGridEvent.subject}`);
    context.log(`Event Time: ${eventGridEvent.eventTime}`);
    context.log(`Data: ${JSON.stringify(eventGridEvent.data)}`);

    // Your custom logic to handle the event
    // For example, process the data, send notifications, update a database, etc.
};
                

Configure Event Grid

After creating your function, you need to configure Event Grid to send events to your function. This is typically done by creating a subscription to an Event Grid topic or domain.

1. Navigate to your Event Grid Topic or Domain in the Azure portal.
2. Under "Events", select "Create a new subscription".
3. In the subscription details:
   • Event Subscription Name: A unique name for your subscription.
   • Event Types: Select the specific event types you want to trigger your function.
   • Endpoint Type: Select "Azure Function".
   • Endpoint: Select your Function App and then the specific Event Grid triggered function you created.
4. Optionally, you can filter events based on the subject or other properties.
5. Click "Create".

Test the trigger

To test your Event Grid trigger, you can simulate an event.

1. You can manually publish an event to your Event Grid topic using tools like Postman, Azure CLI, or by triggering an action in another Azure service that publishes events to Event Grid (e.g., creating a blob in a storage account).
2. Check your Function App's logs in the Azure portal or Application Insights to see the incoming event details and verify that your function executed successfully.

Important Considerations

• Event Schema: The Event Grid trigger binds to the standard EventGridEvent schema. Understand the structure of the events you are expecting.
• Idempotency: Design your function to be idempotent, as Event Grid may deliver events more than once.
• Error Handling: Implement robust error handling and retry mechanisms. If your function fails to process an event, Event Grid might retry delivery based on its configuration.
• Security: Secure your Function App using managed identities or API keys, and configure Event Grid subscriptions with appropriate authentication.
• Scale: Azure Functions scales automatically based on incoming event volume.
• Batching: For certain event types, Event Grid might batch events. Your function should be able to handle a batch of events if necessary.

For more detailed information, refer to the official Azure Functions documentation and the Azure Event Grid documentation.