Connect to Azure Web PubSub

This page describes how consuming apps connect to an Azure Web PubSub resource that’s already modeled in your AppHost. For the AppHost API surface — adding a Web PubSub resource, hubs, event handlers, role assignments, and more — see Azure Web PubSub Hosting integration.

When you reference an Azure Web PubSub resource from your AppHost, Aspire injects the connection information into the consuming app as environment variables. Your app can either read those environment variables directly — the pattern works the same from any language — or, in C#, use the Aspire Azure Web PubSub client integration for automatic dependency injection, health checks, and telemetry.

Connection properties

Aspire exposes each property as an environment variable named [RESOURCE]_[PROPERTY]. For instance, the Uri property of a resource called web-pubsub becomes WEB_PUBSUB_URI.

The Azure Web PubSub resource exposes the following connection properties:

Property Name	Description
Uri	The HTTPS service endpoint, with the format https://{resource-name}.webpubsub.azure.com

Example:

WEB_PUBSUB_URI: https://webpubsub-abc123.webpubsub.azure.com

Connection string formats

Azure Web PubSub clients accept two connection formats:

• Service endpoint (recommended): Uses the endpoint URL with a managed identity / default credential. This is the format Aspire injects by default.

  https://{account_name}.webpubsub.azure.com

• Full connection string (includes access key): Combines the Endpoint and AccessKey components. Use this only when managed identity isn’t available.

  Endpoint=https://{account_name}.webpubsub.azure.com;AccessKey={account_key}

Tip

Role-based access (managed identity) is the recommended approach for production. Aspire provisions a WebPubSubServiceOwner role assignment for your app automatically. See Assign Azure Web PubSub roles.

Connect from your app

Pick the language your consuming app is written in. Each example assumes your AppHost adds an Azure Web PubSub resource named web-pubsub and references it from the consuming app.

C#

For C# apps, the recommended approach is the Aspire Azure Web PubSub client integration. It registers a WebPubSubServiceClient through dependency injection and adds health checks and telemetry automatically. If you’d rather read environment variables directly, see the Read environment variables section at the end of this tab.

Install the client integration

Install the 📦 Aspire.Azure.Messaging.WebPubSub NuGet package in the client-consuming project:

.NET CLI

.NET CLI — Add Aspire.Azure.Messaging.WebPubSub package

dotnet add package Aspire.Azure.Messaging.WebPubSub

Program.cs (C# file-based app)

Program.cs

#:package Aspire.Azure.Messaging.WebPubSub@*

PackageReference (*.csproj)

XML — Add Aspire.Azure.Messaging.WebPubSub package reference

<PackageReference Include="Aspire.Azure.Messaging.WebPubSub" Version="*" />

Add the Web PubSub service client

In Program.cs, call AddAzureWebPubSubServiceClient on your IHostApplicationBuilder to register a WebPubSubServiceClient:

C# — Program.cs

builder.AddAzureWebPubSubServiceClient(
    connectionName: "web-pubsub",
    settings => settings.HubName = "messages");

Tip

The connectionName must match the Azure Web PubSub resource name from the AppHost. For more information, see Add Azure Web PubSub resource.

Resolve the client through dependency injection:

C# — ExampleService.cs

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

Add keyed Web PubSub clients

To register multiple WebPubSubServiceClient instances for different hubs, use AddKeyedAzureWebPubSubServiceClient:

C# — Program.cs

builder.AddKeyedAzureWebPubSubServiceClient(name: "messages");
builder.AddKeyedAzureWebPubSubServiceClient(name: "commands");

Bemærk

When using keyed services, your Web PubSub resource must be configured with two named hubs, one for messages and one for commands.

Then resolve each client by key:

C# — ExampleService.cs

public class ExampleService(
    [FromKeyedServices("messages")] WebPubSubServiceClient messagesClient,
    [FromKeyedServices("commands")] WebPubSubServiceClient commandsClient)
{
    // Use clients...
}

Configuration

The Aspire Azure Web PubSub client integration offers multiple ways to provide configuration.

Connection strings. When using a connection string from the ConnectionStrings configuration section, pass the connection name to AddAzureWebPubSubServiceClient. Two formats are supported:

• Service endpoint (recommended):

  JSON — appsettings.json

  {
    "ConnectionStrings": {
      "web-pubsub": "https://{account_name}.webpubsub.azure.com"
    }
  }

• Full connection string with access key:

  JSON — appsettings.json

  {
    "ConnectionStrings": {
      "web-pubsub": "Endpoint=https://{account_name}.webpubsub.azure.com;AccessKey={account_key}"
    }
  }

Configuration providers. The client integration supports Microsoft.Extensions.Configuration. It loads AzureMessagingWebPubSubSettings from appsettings.json using the Aspire:Azure:Messaging:WebPubSub key:

JSON — appsettings.json

{
  "Aspire": {
    "Azure": {
      "Messaging": {
        "WebPubSub": {
          "HubName": "messages",
          "DisableHealthChecks": false
        }
      }
    }
  }
}

Inline delegates. Pass an Action<AzureMessagingWebPubSubSettings> to configure settings inline:

C# — Program.cs

builder.AddAzureWebPubSubServiceClient(
    "web-pubsub",
    settings => settings.DisableHealthChecks = true);

Client integration health checks

Aspire client integrations enable health checks by default. The Azure Web PubSub client integration registers a health check that verifies the service is reachable. The health check is wired into the /health HTTP endpoint, where all registered health checks must pass before the app is considered ready to accept traffic.

Observability and telemetry

The Aspire Azure Web PubSub client integration automatically configures logging, tracing, and metrics through OpenTelemetry.

Logging categories:

• Azure
• Azure.Core
• Azure.Identity
• Azure.Messaging.WebPubSub

Tracing activities:

• Azure.Messaging.WebPubSub.*

Metrics: The Azure Web PubSub integration currently doesn’t support metrics by default due to limitations in the Azure SDK for .NET.

Read environment variables in C#

If you prefer not to use the Aspire client integration, you can read the Aspire-injected endpoint URI from the environment and create a WebPubSubServiceClient directly:

C# — Program.cs

using Azure.Messaging.WebPubSub;
using Azure.Identity;

var endpoint = new Uri(Environment.GetEnvironmentVariable("WEB_PUBSUB_URI")!);
var client = new WebPubSubServiceClient(endpoint, "messages", new DefaultAzureCredential());

// Use client...

Go

Install the Azure Web PubSub SDK for Go:

Terminal

go get github.com/Azure/azure-sdk-for-go/sdk/messaging/webpubsub
go get github.com/Azure/azure-sdk-for-go/sdk/azidentity

Read the injected environment variable and connect using managed identity:

Go — main.go

package main

import (
    "os"
    "github.com/Azure/azure-sdk-for-go/sdk/azidentity"
    "github.com/Azure/azure-sdk-for-go/sdk/messaging/webpubsub"
)

func main() {
    // Read the Aspire-injected service endpoint
    endpoint := os.Getenv("WEB_PUBSUB_URI")

    cred, err := azidentity.NewDefaultAzureCredential(nil)
    if err != nil {
        panic(err)
    }

    client, err := webpubsub.NewClient(endpoint, cred, nil)
    if err != nil {
        panic(err)
    }

    hubClient, err := client.NewHubClient("messages", nil)
    if err != nil {
        panic(err)
    }

    _ = hubClient
    // Use hubClient to send messages...
}

Python

Install the azure-messaging-webpubsubservice package:

Terminal

pip install azure-messaging-webpubsubservice azure-identity

Read the injected environment variable and connect using managed identity:

Python — app.py

import os
from azure.identity import DefaultAzureCredential
from azure.messaging.webpubsubservice import WebPubSubServiceClient

# Read the Aspire-injected service endpoint
endpoint = os.getenv("WEB_PUBSUB_URI")

client = WebPubSubServiceClient(endpoint=endpoint, hub="messages", credential=DefaultAzureCredential())

# Use client to send messages...

Or use a full connection string with access key:

Python — app.py (connection string)

import os
from azure.messaging.webpubsubservice import WebPubSubServiceClient

connection_string = os.getenv("AZURE_WEB_PUBSUB_CONNECTION_STRING")
client = WebPubSubServiceClient.from_connection_string(connection_string, hub="messages")

# Use client...

TypeScript

Install the @azure/web-pubsub package:

Terminal

npm install @azure/web-pubsub @azure/identity

Read the injected environment variable and connect using managed identity:

TypeScript — index.ts

import { WebPubSubServiceClient } from '@azure/web-pubsub';
import { DefaultAzureCredential } from '@azure/identity';

// Read the Aspire-injected service endpoint
const endpoint = process.env.WEB_PUBSUB_URI!;

const client = new WebPubSubServiceClient(
    endpoint,
    new DefaultAzureCredential(),
    "messages" // hub name
);

// Use client to send messages...

Or use a full connection string with access key:

TypeScript — Connect with connection string

import { WebPubSubServiceClient } from '@azure/web-pubsub';

const connectionString = process.env.AZURE_WEB_PUBSUB_CONNECTION_STRING!;
const client = new WebPubSubServiceClient(connectionString, "messages");

// Use client...

Tip

If your app expects specific environment variable names different from the Aspire defaults, you can pass individual connection properties from the AppHost using WithEnvironment. See Customize provisioning infrastructure in the Hosting integration reference.