Set up Azure Event Hubs in the AppHost

This article is the reference for the Aspire Azure Event Hubs Hosting integration. It enumerates the AppHost APIs — with examples for both AppHost.cs and apphost.ts — that you use to model an Azure Event Hubs namespace and its hubs in your AppHost project.

If you’re new to the Azure Event Hubs integration, start with the Get started with Azure Event Hubs integrations guide. For how consuming apps read the connection information this page exposes, see Connect to Azure Event Hubs.

The hosting integration models the following types:

• AzureEventHubsResource: A top-level namespace resource that holds hubs and carries connection information.
• AzureEventHubResource: A single Event Hub within a namespace.
• AzureEventHubsEmulatorResource: The local Event Hubs emulator running as a container.
• AzureEventHubConsumerGroupResource: A consumer group within a hub.

Installation

To start building an Aspire app that uses Azure Event Hubs, install the 📦 Aspire.Hosting.Azure.EventHubs NuGet package:

C#

Terminal

aspire add azure-event-hubs

Learn more about aspire add in the command reference.

Or, choose a manual installation approach:

C# — AppHost.cs

#:package Aspire.Hosting.Azure.EventHubs@*

XML — AppHost.csproj

<PackageReference Include="Aspire.Hosting.Azure.EventHubs" Version="*" />

TypeScript

Terminal

aspire add azure-event-hubs

Learn more about aspire add in the command reference.

This updates your aspire.config.json with the Azure Event Hubs hosting integration package:

aspire.config.json

{
  "packages": {
    "Aspire.Hosting.Azure.EventHubs": "13.3.0"
  }
}

Add an Azure Event Hubs resource

Once you’ve installed the hosting integration, call AddAzureEventHubs to declare a namespace, then call AddHub to declare one or more hubs inside it:

C#

C# — AppHost.cs

var builder = DistributedApplication.CreateBuilder(args);

var eventHubs = builder.AddAzureEventHubs("event-hubs");
eventHubs.AddHub("messages");

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

// After adding all resources, run the app...

TypeScript

TypeScript — apphost.ts

import { createBuilder } from './.modules/aspire.js';

const builder = await createBuilder();

const eventHubs = await builder.addAzureEventHubs("event-hubs");
await eventHubs.addHub("messages");

await builder.addNodeApp("api", "./api", "index.js")
    .withReference(eventHubs);

// After adding all resources, run the app...

The preceding code adds an Azure Event Hubs namespace named event-hubs with an Event Hub named messages. The WithReference (or withReference) method injects the connection information into the consuming project.

Precaución

When you call AddAzureEventHubs, it implicitly calls AddAzureProvisioning — which adds support for generating Azure resources dynamically during app startup. The app must configure the appropriate subscription and location. For more information, see Local provisioning: Configuration.

Nota

When you reference an Azure Event Hubs resource from the AppHost, Aspire makes several properties available to the consuming project, such as connection URIs and hub names. For a complete list of these properties and per-language connection examples, see Connect to Azure Event Hubs.

Add an Event Hub consumer group

To add a consumer group to a hub, call AddConsumerGroup (or addConsumerGroup) on the hub resource builder:

C#

C# — AppHost.cs

var builder = DistributedApplication.CreateBuilder(args);

var eventHubs = builder.AddAzureEventHubs("event-hubs");
var messages = eventHubs.AddHub("messages");
messages.AddConsumerGroup("messagesConsumer");

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

// After adding all resources, run the app...

TypeScript

TypeScript — apphost.ts

import { createBuilder } from './.modules/aspire.js';

const builder = await createBuilder();

const eventHubs = await builder.addAzureEventHubs("event-hubs");
const messages = await eventHubs.addHub("messages");
await messages.addConsumerGroup("messagesConsumer");

await builder.addNodeApp("api", "./api", "index.js")
    .withReference(eventHubs);

// After adding all resources, run the app...

The AddConsumerGroup call registers a consumer group named messagesConsumer on the messages hub. For more information, see Azure Event Hubs: Consumer groups.

Run as emulator

The hosting integration supports running Event Hubs locally using the mcr.microsoft.com/azure-messaging/eventhubs-emulator/latest container image. This lets you develop and test without an Azure subscription or an existing Event Hubs namespace.

C#

C# — AppHost.cs

var builder = DistributedApplication.CreateBuilder(args);

var eventHubs = builder.AddAzureEventHubs("event-hubs")
    .RunAsEmulator();

eventHubs.AddHub("messages");

builder.AddProject<Projects.ExampleProject>()
    .WithReference(eventHubs);

// After adding all resources, run the app...

TypeScript

TypeScript — apphost.ts

import { createBuilder } from './.modules/aspire.js';

const builder = await createBuilder();

const eventHubs = await builder.addAzureEventHubs("event-hubs")
    .runAsEmulator();

await eventHubs.addHub("messages");

await builder.addNodeApp("api", "./api", "index.js")
    .withReference(eventHubs);

// After adding all resources, run the app...

For more information, see Azure Event Hubs Emulator.

Configure the emulator host port

By default, the emulator container exposes port 5672 mapped to a random host port:

Endpoint	Container image	Container port	Host port
emulator	mcr.microsoft.com/azure-messaging/eventhubs-emulator/latest	5672	dynamic

To fix the host port, pass a configureContainer callback and call WithHostPort (or withHostPort):

C#

C# — AppHost.cs

var builder = DistributedApplication.CreateBuilder(args);

var eventHubs = builder.AddAzureEventHubs("event-hubs")
    .RunAsEmulator(emulator =>
    {
        emulator.WithHostPort(7777);
    });

eventHubs.AddHub("messages");

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

// After adding all resources, run the app...

TypeScript

TypeScript — apphost.ts

import { createBuilder } from './.modules/aspire.js';

const builder = await createBuilder();

const eventHubs = await builder.addAzureEventHubs("event-hubs")
    .runAsEmulator({
        configureContainer: async (emulator) => {
            await emulator.withHostPort({ port: 7777 });
        },
    });

await eventHubs.addHub("messages");

await builder.addNodeApp("api", "./api", "index.js")
    .withReference(eventHubs);

// After adding all resources, run the app...

The emulator container’s port mapping is then fixed:

Endpoint name	Port mapping (container:host)
emulator	5672:7777

Add a data volume to the emulator

C#

C# — AppHost.cs

var builder = DistributedApplication.CreateBuilder(args);

var eventHubs = builder.AddAzureEventHubs("event-hubs")
    .RunAsEmulator(emulator =>
    {
        emulator.WithDataVolume();
    });

eventHubs.AddHub("messages");

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

// After adding all resources, run the app...

TypeScript

The TypeScript AppHost doesn’t currently expose withDataVolume on the Event Hubs emulator resource. To persist emulator state across restarts from a TypeScript AppHost, use withConfigurationFile to pre-configure hubs or run the C# AppHost instead.

The data volume persists emulator state outside the container’s lifecycle. The volume is mounted at /data inside the container. A random name is generated unless you pass a name parameter. For more information, see Docker docs: Volumes.

Add a data bind mount to the emulator

C#

C# — AppHost.cs

var builder = DistributedApplication.CreateBuilder(args);

var eventHubs = builder.AddAzureEventHubs("event-hubs")
    .RunAsEmulator(emulator =>
    {
        emulator.WithDataBindMount("/path/to/data");
    });

eventHubs.AddHub("messages");

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

// After adding all resources, run the app...

TypeScript

The TypeScript AppHost doesn’t currently expose withDataBindMount on the Event Hubs emulator resource. Use a data volume via the C# AppHost or pre-configure hubs with withConfigurationFile instead.

Data bind mounts rely on the host machine’s filesystem. For more information, see Docker docs: Bind mounts.

Configure the emulator with a JSON file

The Event Hubs emulator starts with a default Config.json. To replace it entirely, call WithConfigurationFile (or withConfigurationFile):

C#

C# — AppHost.cs

var builder = DistributedApplication.CreateBuilder(args);

var eventHubs = builder.AddAzureEventHubs("event-hubs")
    .RunAsEmulator(emulator =>
    {
        emulator.WithConfigurationFile("./messaging/custom-config.json");
    });

eventHubs.AddHub("messages");

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

// After adding all resources, run the app...

TypeScript

TypeScript — apphost.ts

import { createBuilder } from './.modules/aspire.js';

const builder = await createBuilder();

const eventHubs = await builder.addAzureEventHubs("event-hubs")
    .runAsEmulator({
        configureContainer: async (emulator) => {
            await emulator.withConfigurationFile("./messaging/custom-config.json");
        },
    });

await eventHubs.addHub("messages");

await builder.addNodeApp("api", "./api", "index.js")
    .withReference(eventHubs);

// After adding all resources, run the app...

The file is mounted at /Eventhubs_Emulator/ConfigFiles/Config.json in the container as a read-only file.

Override specific emulator configuration properties

To update individual properties in the default configuration rather than replacing the entire file, call WithConfiguration in C#:

C# — AppHost.cs

var builder = DistributedApplication.CreateBuilder(args);

var eventHubs = builder.AddAzureEventHubs("event-hubs")
    .RunAsEmulator(emulator =>
    {
        emulator.WithConfiguration(
            (JsonNode configuration) =>
            {
                var userConfig = configuration["UserConfig"];
                var ns = userConfig["NamespaceConfig"][0];
                var firstEntity = ns["Entities"][0];

                firstEntity["PartitionCount"] = 5;
            });
    });

eventHubs.AddHub("messages");

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

// After adding all resources, run the app...

Nota

WithConfiguration is not available in the TypeScript AppHost. Use withConfigurationFile to supply a fully customized configuration file instead.

Connect to an existing Azure Event Hubs namespace

If you already have an Azure Event Hubs namespace, call AsExisting (or asExisting) instead of provisioning a new one:

C#

C# — AppHost.cs

var builder = DistributedApplication.CreateBuilder(args);

var existingName = builder.AddParameter("existingEventHubsName");
var existingResourceGroup = builder.AddParameter("existingEventHubsResourceGroup");

var eventHubs = builder.AddAzureEventHubs("event-hubs")
    .AsExisting(existingName, existingResourceGroup);

builder.AddProject<Projects.ExampleProject>()
    .WithReference(eventHubs);

// After adding all resources, run the app...

TypeScript

TypeScript — apphost.ts

import { createBuilder } from './.modules/aspire.js';

const builder = await createBuilder();

const existingName = await builder.addParameter("existingEventHubsName");

const eventHubs = await builder.addAzureEventHubs("event-hubs")
    .asExisting(existingName);

await builder.addNodeApp("api", "./api", "index.js")
    .withReference(eventHubs);

// After adding all resources, run the app...

For more information, see Use existing Azure resources.

Nota

Alternatively, you can add a connection string to the AppHost directly. This approach is weakly-typed and doesn’t work with role assignments or infrastructure customizations. For more information, see Add existing Azure resources with connection strings.

Role-based access

Azure Event Hubs uses role-based access control (RBAC). The hosting integration assigns roles automatically when you provision a new namespace. The default role assigned to the managed identity is AzureEventHubsDataOwner.

To customise role assignments, call withRoleAssignments:

C#

C# — AppHost.cs

var builder = DistributedApplication.CreateBuilder(args);

var eventHubs = builder.AddAzureEventHubs("event-hubs");

builder.AddProject<Projects.ExampleService>()
    .WithReference(eventHubs)
    .WithRoleAssignments(eventHubs, AzureEventHubsRole.AzureEventHubsDataSender);

// After adding all resources, run the app...

TypeScript

TypeScript — apphost.ts

import { createBuilder, AzureEventHubsRole } from './.modules/aspire.js';

const builder = await createBuilder();

const eventHubs = await builder.addAzureEventHubs("event-hubs");
await eventHubs.addHub("messages");

const api = await builder.addNodeApp("api", "./api", "index.js")
    .withReference(eventHubs);

await eventHubs.withRoleAssignments(api, [AzureEventHubsRole.AzureEventHubsDataSender]);

// After adding all resources, run the app...

The available roles are:

Role	Description
AzureEventHubsDataOwner	Full access to Azure Event Hubs resources
AzureEventHubsDataReceiver	Receive access to Azure Event Hubs resources
AzureEventHubsDataSender	Send access to Azure Event Hubs resources

Provisioning-generated Bicep

If you’re new to Bicep, it’s a domain-specific language for defining Azure resources. With Aspire, you don’t need to write Bicep by hand — the provisioning APIs generate it for you. When you publish your app, the generated Bicep is written alongside the manifest file. When you add an Azure Event Hubs resource, the following Bicep is generated:

Generated Bicep — event-hubs.bicep

@description('The location for the resource(s) to be deployed.')
param location string = resourceGroup().location

param sku string = 'Standard'

resource event_hubs 'Microsoft.EventHub/namespaces@2024-01-01' = {
  name: take('event_hubs-${uniqueString(resourceGroup().id)}', 256)
  location: location
  properties: {
    disableLocalAuth: true
  }
  sku: {
    name: sku
  }
  tags: {
    'aspire-resource-name': 'event-hubs'
  }
}

resource messages 'Microsoft.EventHub/namespaces/eventhubs@2024-01-01' = {
  name: 'messages'
  parent: event_hubs
}

output eventHubsEndpoint string = event_hubs.properties.serviceBusEndpoint

output name string = event_hubs.name

Role assignments are generated in a separate module:

Generated Bicep — event-hubs-roles.bicep

@description('The location for the resource(s) to be deployed.')
param location string = resourceGroup().location

param event_hubs_outputs_name string

param principalType string

param principalId string

resource event_hubs 'Microsoft.EventHub/namespaces@2024-01-01' existing = {
  name: event_hubs_outputs_name
}

resource event_hubs_AzureEventHubsDataOwner 'Microsoft.Authorization/roleAssignments@2022-04-01' = {
  name: guid(event_hubs.id, principalId, subscriptionResourceId('Microsoft.Authorization/roleDefinitions', 'f526a384-b230-433a-b45c-95f59c4a2dec'))
  properties: {
    principalId: principalId
    roleDefinitionId: subscriptionResourceId('Microsoft.Authorization/roleDefinitions', 'f526a384-b230-433a-b45c-95f59c4a2dec')
    principalType: principalType
  }
  scope: event_hubs
}

The generated Bicep is a starting point — customise it through the C# provisioning APIs, not by editing the file directly, as direct edits are overwritten on the next publish.

Customize provisioning infrastructure

All Aspire Azure resources subclass AzureProvisioningResource. The ConfigureInfrastructure (or configureInfrastructure) API lets you customise the generated Bicep with a fluent callback:

C#

C# — AppHost.cs

var builder = DistributedApplication.CreateBuilder(args);

builder.AddAzureEventHubs("event-hubs")
    .ConfigureInfrastructure(infra =>
    {
        var eventHubs = infra.GetProvisionableResources()
                              .OfType<EventHubsNamespace>()
                              .Single();

        eventHubs.Sku = new EventHubsSku()
        {
            Name = EventHubsSkuName.Premium,
            Tier = EventHubsSkuTier.Premium,
            Capacity = 7,
        };
        eventHubs.PublicNetworkAccess = EventHubsPublicNetworkAccess.SecuredByPerimeter;
        eventHubs.Tags.Add("ExampleKey", "Example value");
    });

TypeScript

TypeScript — apphost.ts

import { createBuilder } from './.modules/aspire.js';

const builder = await createBuilder();

const eventHubs = await builder.addAzureEventHubs("event-hubs");
await eventHubs.configureInfrastructure(async (infra) => {
    // Modify infra resources here using the AzureResourceInfrastructure API
});

// After adding all resources, run the app...

The preceding C# code:

• Retrieves the EventHubsNamespace from the provisionable resources.
• Sets the SKU to Premium with a capacity of 7.
• Sets PublicNetworkAccess to SecuredByPerimeter.
• Adds a tag with key ExampleKey and value Example value.

For more configuration options, see Azure.Provisioning customization.

Connection properties

For the full reference of Azure Event Hubs connection properties — and how consuming apps in C#, TypeScript, Python, and Go read them — see Connect to Azure Event Hubs.

Hosting integration health checks

The Azure Event Hubs hosting integration automatically adds a health check for the Event Hubs resource. The health check verifies that the Event Hubs namespace is running and that a connection can be established to it.

The hosting integration relies on the 📦 AspNetCore.HealthChecks.Azure.Messaging.EventHubs NuGet package.