How to use event grid with functions

AzureHow-ToBeginner · 4 min read

How to Use Azure Event Grid with Functions: Simple Guide

To use Azure Event Grid with Azure Functions, create a function with an Event Grid trigger and subscribe it to an Event Grid topic or system event. This setup allows your function to automatically run when events are published to the grid, enabling event-driven processing.

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Syntax

The basic syntax involves creating an Azure Function with an EventGridTrigger. This trigger listens for events from Event Grid and passes event data to the function.

EventGridTrigger: Attribute that marks the function to respond to Event Grid events.
EventGridEvent: The event data passed to the function.
FunctionName: The name of your Azure Function.

csharp

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

public static class EventGridFunction
{
    [FunctionName("EventGridFunction")]
    public static void Run([EventGridTrigger] EventGridEvent eventGridEvent, ILogger log)
    {
        log.LogInformation($"Event received: {eventGridEvent.EventType}");
    }
}

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Example

This example shows a complete Azure Function that triggers on Event Grid events and logs the event type and data. It demonstrates how to handle incoming events from Event Grid.

csharp

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

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

Output

Event Type: Microsoft.Storage.BlobCreated Event Data: {"api":"PutBlob","clientRequestId":"...","requestId":"...","eTag":"...","contentType":"text/plain","contentLength":524288,"blobType":"BlockBlob","url":"https://..."}

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Common Pitfalls

Not setting up Event Grid subscription: Your function won't receive events unless you subscribe it to the Event Grid topic or system event.
Incorrect function binding: Using the wrong trigger attribute or missing the EventGridTrigger causes the function not to trigger.
Missing permissions: The function app must have permission to access the Event Grid topic or system events.
Ignoring event schema: Event data must be parsed correctly according to the event schema.

csharp

/* Wrong: Missing EventGridTrigger attribute */
[FunctionName("WrongFunction")]
public static void Run(string eventData, ILogger log)
{
    log.LogInformation("This won't trigger on Event Grid events.");
}

/* Correct: Using EventGridTrigger */
[FunctionName("CorrectFunction")]
public static void Run([EventGridTrigger] EventGridEvent eventGridEvent, ILogger log)
{
    log.LogInformation($"Event received: {eventGridEvent.EventType}");
}

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Quick Reference

Remember these key points when using Event Grid with Functions:

Create an Azure Function with EventGridTrigger.
Subscribe the function to Event Grid topics or system events.
Ensure your function app has the right permissions.
Parse event data according to the event schema.

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Key Takeaways

Use the EventGridTrigger attribute to make your Azure Function respond to Event Grid events.

Subscribe your function to the correct Event Grid topic or system event to receive events.

Ensure your function app has permissions to access Event Grid resources.

Parse event data carefully based on the event schema to handle events correctly.

Avoid missing the trigger attribute or subscription setup to prevent silent failures.