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.NET Aspire Azure Event Hubs integration

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In this article, you learn how to use the .NET Aspire Azure Event Hubs integration. The Aspire.Azure.Messaging.EventHubs library offers options for registering the following types:

These type are registered in the DI container for connecting to Azure Event Hubs.

Prerequisites

Get started

To get started with the .NET Aspire Azure Event Hubs integration, install the Aspire.Azure.Messaging.EventHubs NuGet package in the client-consuming project, i.e., the project for the application that uses the Azure Event Hubs client.

dotnet add package Aspire.Azure.Messaging.EventHubs

For more information, see dotnet add package or Manage package dependencies in .NET applications.

Supported clients with options classes

The following clients are supported by the library, along with their corresponding options and settings classes:

Azure Client type Azure Options class .NET Aspire Settings class
EventHubProducerClient EventHubProducerClientOptions AzureMessagingEventHubsProducerSettings
EventHubBufferedProducerClient EventHubBufferedProducerClientOptions AzureMessagingEventHubsBufferedProducerSettings
EventHubConsumerClient EventHubConsumerClientOptions AzureMessagingEventHubsConsumerSettings
EventProcessorClient EventProcessorClientOptions AzureMessagingEventHubsProcessorSettings
PartitionReceiver PartitionReceiverOptions AzureMessagingEventHubsPartitionReceiverSettings

The client type are from the Azure SDK for .NET, as are the corresponding options classes. The settings classes are provided by the .NET Aspire Azure Event Hubs integration library.

Example usage

The following example assumes that you have an Azure Event Hubs namespace and an Event Hub created and wish to configure an EventHubProducerClient to send events to the Event Hub. The EventHubBufferedProducerClient, EventHubConsumerClient, EventProcessorClient, and PartitionReceiverare configured in a similar manner.

In the Program.cs file of your client-consuming project, call the AddAzureEventHubProducerClient extension to register a EventHubProducerClient for use via the dependency injection container.

builder.AddAzureEventHubProducerClient("eventHubsConnectionName");

You can then retrieve the EventHubProducerClient instance using dependency injection. For example, to retrieve the client from a service:

public class ExampleService(EventHubProducerClient client)
{
    // Use client...
}

For more information, see the Azure.Messaging.EventHubs documentation for examples on using the EventHubProducerClient.

App host usage

To add Azure Event Hub hosting support to your IDistributedApplicationBuilder, install the Aspire.Hosting.Azure.EventHubs NuGet package in the app host project.

dotnet add package Aspire.Hosting.Azure.EventHubs

In your app host project, add an Event Hubs connection and an Event Hub resource and consume the connection using the following methods:

var builder = DistributedApplication.CreateBuilder(args);

var eventHubs = builder.AddAzureEventHubs("eventHubsConnectionName")
                       .AddEventHub("MyHub");

var exampleService = builder.AddProject<Projects.ExampleService>()
                            .WithReference(eventHubs);

The AddAzureEventHubs method will read connection information from the AppHost's configuration (for example, from "user secrets") under the ConnectionStrings:eventHubsConnectionName config key. The WithReference method passes that connection information into a connection string named eventHubsConnectionName in the ExampleService project.

As of .NET Aspire 8.1, the Azure EventHubs extension for .NET Aspire supports launching a local emulator for EventHubs. You can use the emulator by applying the RunAsEmulator() extension method as follows:

var eventHubs = builder.AddAzureEventHubs("eventHubsConnectionName")
                       .RunAsEmulator()
                       .AddEventHub("MyHub");

The emulator for Azure EventHubs results in two container resources being launched inside .NET Aspire derived from the name of the Event Hubs resource name.

Important

Even though we are creating an Event Hub using the AddEventHub at the same time as the namespace, as of .NET Aspire version preview-5, the connection string will not include the EntityPath property, so the EventHubName property must be set in the settings callback for the preferred client. Future versions of Aspire will include the EntityPath property in the connection string and will not require the EventHubName property to be set in this scenario.

In the Program.cs file of ExampleService, the connection can be consumed using by calling of the supported Event Hubs client extension methods:

builder.AddAzureEventProcessorClient(
    "eventHubsConnectionName",
    static settings =>
    {
        settings.EventHubName = "MyHub";
    });

Configuration

The .NET Aspire Azure Event Hubs library provides multiple options to configure the Azure Event Hubs connection based on the requirements and conventions of your project. Either a FullyQualifiedNamespace or a ConnectionString is a required to be supplied.

Use a connection string

When using a connection string from the ConnectionStrings configuration section, provide the name of the connection string when calling builder.AddAzureEventHubProducerClient() and other supported Event Hubs clients. In this example, the connection string does not include the EntityPath property, so the EventHubName property must be set in the settings callback:

builder.AddAzureEventHubProducerClient(
    "eventHubsConnectionName",
    static settings =>
    {
        settings.EventHubName = "MyHub";
    });

And then the connection information will be retrieved from the ConnectionStrings configuration section. Two connection formats are supported:

Fully Qualified Namespace (FQN)

The recommended approach is to use a fully qualified namespace, which works with the AzureMessagingEventHubsSettings.Credential property to establish a connection. If no credential is configured, the DefaultAzureCredential is used.

{
  "ConnectionStrings": {
    "eventHubsConnectionName": "{your_namespace}.servicebus.windows.net"
  }
}

Connection string

Alternatively, use a connection string:

{
  "ConnectionStrings": {
    "eventHubsConnectionName": "Endpoint=sb://mynamespace.servicebus.windows.net/;SharedAccessKeyName=accesskeyname;SharedAccessKey=accesskey;EntityPath=MyHub"
  }
}

Use configuration providers

The .NET Aspire Azure Event Hubs library supports Microsoft.Extensions.Configuration. It loads the AzureMessagingEventHubsSettings and the associated Options, e.g. EventProcessorClientOptions, from configuration by using the Aspire:Azure:Messaging:EventHubs: key prefix, followed by the name of the specific client in use. For example, consider the appsettings.json that configures some of the options for an EventProcessorClient:

{
  "Aspire": {
    "Azure": {
      "Messaging": {
        "EventHubs": {
          "EventProcessorClient": {
            "EventHubName": "MyHub",
            "ClientOptions": {
              "Identifier": "PROCESSOR_ID"
            }
          }
        }
      }
    }
  }
}

You can also setup the Options type using the optional Action<IAzureClientBuilder<EventProcessorClient, EventProcessorClientOptions>> configureClientBuilder parameter of the AddAzureEventProcessorClient method. For example, to set the processor's client ID for this client:

builder.AddAzureEventProcessorClient(
    "eventHubsConnectionName",
    configureClientBuilder: clientBuilder => clientBuilder.ConfigureOptions(
        options => options.Identifier = "PROCESSOR_ID"));

Observability and telemetry

.NET Aspire integrations automatically set up Logging, Tracing, and Metrics configurations, which are sometimes known as the pillars of observability. For more information about integration observability and telemetry, see .NET Aspire integrations overview. Depending on the backing service, some integrations may only support some of these features. For example, some integrations support logging and tracing, but not metrics. Telemetry features can also be disabled using the techniques presented in the Configuration section.

Logging

The .NET Aspire Azure Event Hubs integration uses the following log categories:

  • Azure.Core
  • Azure.Identity

Tracing

The .NET Aspire Azure Event Hubs integration will emit the following tracing activities using OpenTelemetry:

  • "Azure.Messaging.EventHubs.*"

Metrics

The .NET Aspire Azure Event Hubs integration currently doesn't support metrics by default due to limitations with the Azure SDK for .NET. If that changes in the future, this section will be updated to reflect those changes.

See also