Implementing Azure Service Bus Topic in a .NET Function App

In this blog we are going to see about Implementing Azure Service Bus Topic in a .NET Function App. Azure Service Bus is a robust messaging service on Azure that enables applications to communicate with each other in a decoupled manner. When dealing with complex scenarios that require high scalability and fault tolerance, Service Bus topics and subscriptions are excellent choices. This blog will guide you through implementing an Azure Service Bus Topic in a .NET Function App.

Prerequisites

Before we start, ensure you have the following:

1. Azure Subscription: Sign up if you don’t have one.
2. Azure Service Bus Namespace: Create a Service Bus Namespace in the Azure portal.
3. Service Bus Topic: Create a topic and a subscription within your Service Bus Namespace.
4. Azure Function App: Create a Function App in the Azure portal.
5. Visual Studio or Visual Studio Code: To write and deploy the function app.

Step 1: Setting Up the Environment

1. Create Azure Service Bus Namespace and Topic

Firstly, go to the Azure portal and create a Service Bus Namespace. Next, create a Topic within the Service Bus Namespace. Additionally, within the Topic, create one or more Subscriptions.

2. Create an Azure Function App

Then, in the Azure portal, create a new Function App. Choose the appropriate runtime stack (e.g., .NET 6). Once created, download the publish profile for deployment later.

Step 2: Create a .NET Function App Project

1. Create a New Project

Open Visual Studio. Create a new Azure Functions project with the following commands:

dotnet new func --name ServiceBusFunctionApp
cd ServiceBusFunctionApp

or create using Visual Studio:

2. Install Required NuGet Packages

Add the necessary NuGet package for Azure Service Bus:

dotnet add package Microsoft.Azure.WebJobs.Extensions.ServiceBus

Step 3: Implement the Function

Open the `Function1.cs` file (or create a new file) and implement the function to handle messages from the Service Bus topic.

using System;
using Microsoft.Azure.WebJobs;
using Microsoft.Azure.WebJobs.ServiceBus;
using Microsoft.Extensions.Logging;

public static class ServiceBusTopicTrigger
{
    [FunctionName("ServiceBusTopicTrigger")]
    public static void Run(
        [ServiceBusTrigger("mytopic", "mysubscription", Connection = "ServiceBusConnectionString")] string mySbMsg,
        ILogger log)
    {
        log.LogInformation($"C# ServiceBus topic trigger function processed message: {mySbMsg}");
    }
}

Step 4: Configure Connection Strings

1. Local Settings

In your `local.settings.json` file, add the Service Bus connection string:
{
  “IsEncrypted”: false,
  “Values”: {
    “AzureWebJobsStorage”: “<your_storage_account_connection_string>”,
    “FUNCTIONS_WORKER_RUNTIME”: “dotnet”,
    “ServiceBusConnectionString”: “<your_service_bus_connection_string>”
  }
}

2. Azure Configuration

When deploying to Azure, make sure to set the `ServiceBusConnectionString` in the Function App settings in the Azure portal.

Step 5: Deploy the Function App

Publish the Project

You can use the publish profile you downloaded earlier to deploy from Visual Studio.

Step 6: Test the Function

1. Send a message to the Service Bus topic using the Azure portal or any Service Bus client.
2. Monitor the logs in the Azure portal to see the function processing the message.

Conclusion

Implementing Azure Service Bus Topic in a .NET Function App provides a scalable and reliable way to handle messages in a decoupled manner. By following the steps outlined in this blog, you can quickly set up and deploy a function that listens to messages on a Service Bus topic, making your architecture more resilient and scalable.

References :

https://learn.microsoft.com/en-us/azure/service-bus-messaging/service-bus-queues-topics-subscriptions

https://athen.tech/azure-functions-with-net/