RabbitMQ With ASP.NET Core - Microservice Communication With MassTransit

This is a common class library for all the applications. Here we have Model (i.e., Todo class) and Constant (For RabbitMQ configuration).

Below is the code snippet for the TodoandConstantclasses.

Todo.cs

using System;
namespace CrossCuttingLayer
{
    public class Todo
    {
        public string Id { get; set; }
        public DateTime CreatedTime { get; set; } = DateTime.UtcNow;
        public string TaskDescription { get; set; }
        public bool IsCompleted { get; set; }
    }

}

RabbitMqConsts.cs

public class RabbitMqConsts
{
    public const string RabbitMqRootUri = "rabbitmq://localhost";
    public const string RabbitMqUri = "rabbitmq://localhost/todoQueue";
    public const string UserName = "guest";
    public const string Password = "guest";
    public const string NotificationServiceQueue = "notification.service";
}

Publisher class library

We will configure MassTransit in a startup.cs file in our Asp.net Core Web API application.

Startup.cs

public void ConfigureServices(IServiceCollection services)
{
    services.AddMassTransit(x =>
    {
        x.AddBus(provider => Bus.Factory.CreateUsingRabbitMq(config =>
        {
            config.Host(new Uri(RabbitMqConsts.RabbitMqRootUri), h =>
            {
                h.Username(RabbitMqConsts.UserName);
                h.Password(RabbitMqConsts.Password);
            });
        }));
    });
    services.AddMassTransitHostedService();
    services.AddControllers();
    services.AddSwaggerGen(c =>
    {
        c.SwaggerDoc("v1", new OpenApiInfo { Title = "Microservice.Todo.Publisher", Version = "v1" });
    });
}

And in our publisher controller, we will create a post method to publish a message.

TodoController.cs

[HttpPost]
public async Task<IActionResult> CreateTicket(Todo todoModel)
{
    if (todoModel is not null)
    {
        Uri uri = new Uri(RabbitMqConsts.RabbitMqUri);
        var endPoint = await _bus.GetSendEndpoint(uri);
        await endPoint.Send(todoModel);
        return Ok();
    }
    return BadRequest();
}

Notification class library

For testing, we will see a console application. In the below code snippet we will register for consumption in the Program.cs file and write consume method in TodoConsumerNotification.cs file to display messages.

static void Main(string[] args)
{
    Console.Title = "Notification";
    var bus = Bus.Factory.CreateUsingRabbitMq(cfg =>
    {
        cfg.Host(new Uri(RabbitMqConsts.RabbitMqRootUri), h =>
        {
            h.Username(RabbitMqConsts.UserName);
            h.Password(RabbitMqConsts.Password);
        });
        cfg.ReceiveEndpoint("todoQueue", ep =>
        {
            ep.PrefetchCount = 16;
            ep.UseMessageRetry(r => r.Interval(2, 100));
            ep.Consumer<TodoConsumerNotification>();
        });

    });
    bus.StartAsync();
    Console.WriteLine("Listening for Todo registered events.. Press enter to exit");
    Console.ReadLine();
    bus.StopAsync();
}

public class TodoConsumerNotification : IConsumer<Todo>
{
    public async Task Consume(ConsumeContext<Todo> context)
    {
        await Console.Out.WriteLineAsync($"Notification sent: todo id {context.Message.Id}");
    }
}

Testing our application

Scenario 1

Keeping Publisher and Consumer/Notification running as Multiple startup projects.

Call post methodAPI/todo via Swagger like the below image.

Output

Scenario 2

Keeping Publisher set as a start-up project and Consumer/Notification running offline.

Call post method API/todo via Swagger like the below image,

You can see that our Queue has 1 new Message Ready which does not deliver yet. It will keep the messages in memory till a consumer is connected.

Let’s bring our Consumer online now, and we can see the message is delivered and Queue is 0.

Summary

In this article, we have gone through Message Brokers, RabbitMQ, Advantages, and Integrating RabbitMQ with ASP.NET Core using MassTransit. We also build a small prototype application to send data over the RabbitMQ Server. Download source code from GitHub