Building Event-Driven Architectures with Azure Event Grid: A Guide to Reacting to Events and Triggering Workflows

Azure Event Grid is a fully-managed event routing service provided by Microsoft that enables developers to build event-driven architectures by reacting to events and triggering workflows in response. With Event Grid, developers can connect to multiple Azure services and third-party services, send events to a variety of endpoints, and respond to events in real-time.

In this article, we will discuss how to use Azure Event Grid to create event-driven architectures and how to use it with Azure Functions and Azure Logic Apps.

Image from Microsoft Doc

How Azure Event Grid works

Azure Event Grid provides a publisher-subscriber model where events are sent from a publisher to one or more subscribers. Publishers are responsible for sending events to Event Grid, while subscribers are responsible for receiving events and processing them. Event Grid routes events from publishers to subscribers based on subscriptions, which define a filter for events that a subscriber wants to receive.

Event Grid supports a variety of event sources, including Azure services like Blob Storage, Azure Functions, and Azure Resource Manager, as well as third-party services like GitHub, Azure DevOps, and SendGrid. Events can be sent to a variety of endpoints, including Azure Functions, Azure Logic Apps, Azure Event Hubs, and custom webhooks.

I. Create an Azure Event Grid topic: An Event Grid topic is a central hub for events that serves as a communication channel between publishers and subscribers. To create an Event Grid topic, we can use the Azure portal, Azure CLI, or Azure PowerShell.

# Azure CLI command to create an Event Grid topic
az eventgrid topic create --name myeventgridtopic --resource-group myresourcegroup --location eastus

II. Define event subscriptions: An event subscription defines the events that a subscriber wants to receive and the endpoint where events should be sent. Subscriptions can be defined for individual events or for a set of events that match a specific filter. To define a subscription, we can use the Azure portal, Azure CLI, or Azure PowerShell.

# Azure CLI command to create an event subscription
az eventgrid event-subscription create --name myeventsubscription --resource-group myresourcegroup --topic-name myeventgridtopic --endpoint-type webhook --endpoint-url https://mywebhookurl

III. Send events to the Event Grid topic: Once we have defined subscriptions, we can start sending events to the Event Grid topic. Events can be sent using the Azure portal, Azure CLI, or Azure PowerShell.

# Azure CLI command to send an event to an Event Grid topic
az eventgrid event publish --topic-name myeventgridtopic --subject "myevent" --data '{ "message": "Hello, world!" }'

IV. Receive events at the endpoint: When an event is sent to the Event Grid topic, it is routed to all subscribers that have defined a subscription for that event. Subscribers can receive events using a variety of endpoints, including Azure Functions and Azure Logic Apps.

Using Azure Functions with Azure Event Grid

Azure Functions is a serverless compute service that allows developers to run code in response to events. With Azure Event Grid, we can use Azure Functions to create event-driven workflows that respond to events in real-time.

To use Azure Functions with Azure Event Grid, we need to follow these steps:

I. Create an Azure Function: An Azure Function is a piece of code that runs in response to an event. To create an Azure Function, we can use the Azure portal, Visual Studio, or Visual Studio Code.

II. Define an event subscription for the Azure Function: To receive events at an Azure Function, we need to define an event subscription for the Event Grid topic. The subscription should specify the Azure Function as the endpoint URL and the event types that we want to receive.

# Azure CLI command to create an event subscription for an Azure Function
az eventgrid event-subscription create --name myfunctionsubscription --resource-group myresourcegroup --topic-name myeventgridtopic --endpoint-type azurefunction --endpoint-url https://myfunctionapp.azurewebsites.net/api/myfunction --subject-begins-with "myevent"

III. Configure the Azure Function to process events: Once we have defined an event subscription for the Azure Function, we need to configure the Function to process events. We can use the Event Grid trigger binding in Azure Functions to automatically bind the function to the Event Grid topic and process events as they are received.

using System.IO;
using Microsoft.Azure.WebJobs;
using Microsoft.Azure.WebJobs.Extensions.EventGrid;
using Microsoft.Extensions.Logging;

public static class Function1
{
    [FunctionName("myfunction")]
    public static void Run([EventGridTrigger]EventGridEvent eventGridEvent, ILogger log)
    {
        log.LogInformation($"Received event with subject: {eventGridEvent.Subject} and data: {eventGridEvent.Data.ToString()} ");
    }
}

IV. Test the Azure Function: Once we have configured the Azure Function, we can test it by sending events to the Event Grid topic and verifying that the Function processes them correctly.

Using Azure Logic Apps with Azure Event Grid

Azure Logic Apps is a cloud-based service that allows developers to create workflows that integrate with a variety of Azure services and third-party services. With Azure Event Grid, we can use Azure Logic Apps to create event-driven workflows that respond to events in real-time.

To use Azure Logic Apps with Azure Event Grid, we need to follow these steps:

I. Create an Azure Logic App: An Azure Logic App is a workflow that defines a series of steps that execute in response to an event. To create an Azure Logic App, we can use the Azure portal.

II. Define an event subscription for the Azure Logic App: To receive events at an Azure Logic App, we need to define an event subscription for the Event Grid topic. The subscription should specify the Logic App as the endpoint URL and the event types that we want to receive.

# Azure CLI command to create an event subscription for an Azure Logic App
az eventgrid event-subscription create --name mylogicappsubscription --resource-group myresourcegroup --topic-name myeventgridtopic --endpoint-type azurelogicapp --endpoint-url https://mylogicapp.azurewebsites.net/workflows/myworkflow --subject-begins-with "myevent"

III. Configure the Azure Logic App to process events: Once we have defined an event subscription for the Azure Logic App, we need to configure the Logic App to process events. We can use the Event Grid trigger in Azure Logic Apps to automatically trigger the workflow when an event is received.

IV. Build the workflow in the Azure Logic App designer: Once we have configured the Azure Logic App, we can build the workflow in the Azure Logic App designer. The designer allows us to define the steps that the workflow should execute when an event is received.

V. Test the Azure Logic App: Once we have built the workflow in the Azure Logic App designer, we can test the Logic App by sending events to the Event Grid topic and verifying that the workflow executes correctly.

Conclusion

Azure Event Grid is a powerful service that allows developers to build event-driven architectures by reacting to events and triggering workflows in response. With Azure Functions and Azure Logic Apps, we can create event-driven workflows that respond to events in real-time and perform automated tasks. By using Event Grid, we can build applications that are more reactive, scalable, and resilient.

In this article, we have seen how to use Azure Event Grid to create event-driven architectures, and how to use it with Azure Functions and Azure Logic Apps. We have also seen how to create event subscriptions and configure Azure Functions and Logic Apps to process events.

With Azure Event Grid, we can easily build event-driven architectures that react to events and perform automated tasks. Whether we need to process IoT data, monitor resources, or integrate with third-party services, Event Grid provides a powerful and flexible platform for building reactive and scalable applications.