How to subscribe Web API on Azure Messages

Question

I have 2 Web APIs developed on ASP.NET Core. The idea is: the WebAPI_1 sends a message to the Azure Service Bus and then WebAPI_2 has to catch this moment and read it shortly after the message is sent. I understand how to catch this moment is I have a console app instead of WebAPI_2, but I am not sure how to subscribe WebAPI_2 on such the event happening in Azure Service Bus. Below is the code where I have WebAPI_1 and the Console App.

WebAPI_1 (Sender):

public class QueueService : IQueueService
{
    private readonly IConfiguration _config;

    public QueueService(IConfiguration config)
    {
        _config = config;
    }

    public async Task SendMessageAsync<T>(T serviceBusMessage, string queueName)
    {
        var queueClient = new QueueClient(_config.GetConnectionString("AzureServiceBus"), queueName);
        string messageBody = JsonSerializer.Serialize(serviceBusMessage);
        var message = new Message(Encoding.UTF8.GetBytes(messageBody));

        await queueClient.SendAsync(message);
    }
}

And this is how I send it:

 await queue.SendMessageAsync(obj, "myqueue");

And this is the Console App (Receiver):

Main(){
        queueClient = new QueueClient(connectionString, queueName);

        var messageHandlerOptions = new MessageHandlerOptions(ExceptionReceivedHandler)
        {
            MaxConcurrentCalls = 1,
            AutoComplete = false
        };

        queueClient.RegisterMessageHandler(ProcessMessagesAsync, messageHandlerOptions);
}

private static async Task ProcessMessagesAsync(Message message, CancellationToken token)
{
    var jsonString = Encoding.UTF8.GetString(message.Body);
    Model obj = JsonSerializer.Deserialize<Model>(jsonString);
    Console.WriteLine($"Person Received: { obj.Field1} { obj.Field2}");

    await queueClient.CompleteAsync(message.SystemProperties.LockToken);
}

But I want WebAPI_2 to be able to receive the messages instead of the Console App. Please advise.

score 0 · Answer 1 · answered Nov 21 '21 at 17:13

Receiving messages requires a continuous job. ASP.NET Core Controller, as you've probably found out, is not the right place as it's not running continuously and is intended to respond to the request. For a continuous execution, a background service, or task, is the right option. ASP.NET Core has an option to run a BackgroundService that could be used for exactly what you need.

There are multiple blog posts with the details in case you want to get some inspiration:

Getting Started With Azure Service Bus Queues And ASP.NET Core Background Services
Using An ASP.NET Core IHostedService To Run Azure Service Bus Subscriptions and Consumers

How to subscribe Web API on Azure Messages

1 Answers1