How to Send & Read Messages with Azure Service Bus Queues in Azure Functions

Introduction

In this article, we are going to discuss Service Bus Queue Trigger in Azure Functions. We are also going to create a simple Azure function to send and read messages from Service bus queues. So we are going to create an HTTP trigger function to send messages to the queue and a Service bus queue trigger function to read messages from the queue.

If you are new to Azure Functions then check out the below articles.

• How To Easily Create Azure Functions Using Azure Portal
• How To Create And Publish Azure Function From Visual Studio
• How to Integrate Dependency Injection In Azure Functions
• How To Integrate Application Insights Into Azure Functions

What is Azure Service Bus?

Azure Service Bus is a message broker service that is hosted on the Azure platform and it provides functionality to publish messages to various applications and also decouple the applications. Azure service bus has two different flavors; i.e. Queues and Topics. Azure Service Bus Queues follow a First-In-First-Out (FIFO) pattern. Queues provide one-way transport like the sender is going to send messages in the queue and the receiver collects messages from the queue. In queues, there is a 1:1 relationship between the sender and receiver. Messages are present in the queue until the receiver processes and completes the messages.

Creating simple Azure Functions to send and read messages from the queue
 

Prerequisites

• Azure account(If you don't have an Azure subscription, create a free trial account).
• Basic knowledge of Azure Functions

Overview of application

We are creating a simple Azure function application that consists of 3 parts.

1. Create Azure Service Bus Queue using Azure Portal
2. Create HTTP trigger Azure Function to send the message into Queue
3. Create a Service Bus Queue trigger Azure function to read a message from Queue
   

Create Azure Service Bus Queue using Azure Portal

Follow the below steps to create a new Service Bus and Queue in Azure.

• Login to Azure and click on the Create a Resource button.
• In the search box type service bus and select it.
  
• Click on the Create button. You will see the Create Namespace page.
  
• Resource Groups are nothing but a container to hold your resources in Azure. Service Bus is one of the resources so if you have already created Resource Group then select that or if haven't created it yet click on Create button and give it a name.
• Namespace holds the multiple queues or topics residing under the Service Bus. Specify a unique name for the namespace.
• Fill out all the required details and click on the Review + Create button.
  
• Review that everything is added properly and finally click on the Create button.
  
• Creating resources will take time so wait for some time to finish the deployment.
  
• Once the deployment is completed you will see the Go to resource button.
  
• Click on the Go to resource button to see our Service Bus resource.
  
• So we have successfully created a new Service Bus. Now next step is to create a Queue. Go to the Queues section in the left panel click on Queue give a unique name for the queue and click on the Create button.
  
• That's it. We have created our first queue.
  

Create HTTP trigger Azure Function to send the message into Queue
 

Prerequisites

Visual Studio 19 with Azure Development workload installed.

So open Visual Studio and Go to File -> New -> Project. Search "Azure Functions" in the search box select the Azure function template and click on Next.

Give a name to the function project and click on Create.

Select the HTTP trigger template set the Authorization level as Anonymous and click on Create.

That's it. We have created our first Azure function. By default the name of the function is Function1.cs so now change it to "SendMessage".

Azure Functions has Triggers and Bindings. Triggers are the ones due to which function code starts executing forex. In the case of an HTTP trigger whenever you make an HTTP request by hitting the function URL the specific function will start its execution. The Azure function must have only one trigger. Bindings are the direction of data coming in or going out from the function. We have In, out, and both types of bindings.

So for our application, we are creating an HTTP Trigger function that takes data and sends it into the Queue. So to send data to the queue we are using an Output binding. To connect with the queue we need a connection string. So let's open the Service bus resource in portal -> Shared Access Policy -> Copy the Primary Connection String under RootManagedSharedAccessKey

First, install the below NuGet package.

Open the local.settings.json file in our function app add a key called "AzureWebJobsServiceBus" and paste the connection string of our Service bus resource.

{
    "IsEncrypted": false,
    "Values": {
        "AzureWebJobsStorage": "UseDevelopmentStorage=true",
        "FUNCTIONS_WORKER_RUNTIME": "dotnet",
        "AzureWebJobsServiceBus": "<replace your RootManageSharedAccessKey here>"
    }
}

Now add the below code to send a message to the queue using output bindings.

using System.IO;
using System.Text;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Http;
using Microsoft.Azure.WebJobs;
using Microsoft.Azure.WebJobs.Extensions.Http;
using Microsoft.Azure.WebJobs.ServiceBus;
using Microsoft.Extensions.Logging;

namespace AzServiceBusDemo
{
    public static class SendMessage
    {
        [FunctionName("SendMessage")]
        [return: ServiceBus("az-queue", EntityType.Queue)]
        public static async Task<string> Run(
            [HttpTrigger(AuthorizationLevel.Anonymous, "post", Route = null)] HttpRequest req,
            ILogger log)
        {
            log.LogInformation("SendMessage function requested");
            string body = string.Empty;
            using (var reader = new StreamReader(req.Body, Encoding.UTF8))
            {
                body = await reader.ReadToEndAsync();
                log.LogInformation($"Message body : {body}");
            }
            log.LogInformation($"SendMessage processed.");
            return body;
        }
    }
}

• From lines 21-28, we are just getting data from the request body & assigning it to a local variable. After that, we are just returning it from function.
• In line 15, since we are using C# for creating a function, we can use ServiceBusAttribute to specify the output bindings. For the attribute constructor i.e. ServiceBus() we just need to pass queue name and type of entity to bind.

Now run the SendMessage function.

To test the function open Postman and hit the About function URL.

Since we logged our request body, we can see the content.

Open queue "az-queue" and we can see the Active message count is now showing as 1.

To check the message content in the queue you can click on Service Bus Explorer(preview) in the left sidebar and then click on Peek and finally click on the message to see the content.

Create a Service Bus Queue trigger Azure function to read a message from Queue

Now the final step is to read a message from the queue i.e. "az-queue". Right-click on the project and click on project -> Click on Add -> Select New Azure Function. Select the Azure function give it a name and click on Add button.

Now select Service Bus Queue Trigger specify the queue name and click on the Add button.

That's it our Service Bus trigger function is created.

using Microsoft.Azure.WebJobs;
using Microsoft.Extensions.Logging;
namespace AzServiceBusDemo
{
    public static class ReadMessageFromQueue
    {
        [FunctionName("ReadMessageFromQueue")]
        public static void Run([ServiceBusTrigger("az-queue")]string myQueueItem, ILogger log)
        {
            log.LogInformation($"C# ServiceBus queue trigger function processed message: {myQueueItem}");
        }
    }
}

Now run our function app. Since we already have one active message in our queue, as soon as the function starts it will read a message from the queue as shown below.

So in this way, we can use Azure functions to send and read messages from Azure Service Bus Queues.

Conclusion

In this article, we have created a new Azure Service Bus instance and added a new queue from the portal. Also, we have created the HTTP trigger Azure function to send messages into the Queue and Service Bus Queue trigger function to read messages from a queue.I really hope that you enjoyed this article, share it with friends and please do not hesitate to send me your thoughts or comments.

Stay tuned for more articles on Azure Functions.

You can follow me on Twitter @sumitkharche01 and LinkedIn

Happy Coding!