MassTransit - What,Why,How

MassTransit is a powerful open-source library tailored for the .NET platform, which serves as a messaging and microservice orchestration framework. Adopting MassTransit for building applications in C# comes with many benefits and is instrumental under various scenarios.

Let's delve into the key reasons and benefits of using MassTransit, and explore some examples of when it should be employed.

• Streamlined Microservice Architecture MassTransit greatly simplifies managing a microservice architecture by allowing services to communicate asynchronously and effectively. It works above message transport systems such as RabbitMQ, Azure Service Bus, or Amazon SQS, orchestrating how messages are moved between services in a distributed system.
• Abstraction & Accessibility Providing an abstraction over the raw message brokers, MassTransit streamlines complex concepts, making them more accessible for developers. This allows individuals to focus on the core business logic rather than the intricacies of the underlying messaging infrastructure.
• Asynchronous Communication & Concurrency With the inherent asynchronous nature of MassTransit, which leverages the Task Parallel Library (TPL), the library can consume messages concurrently, ensuring that applications can handle a high volume of data without blocking critical processes.
• Variety of Messaging Patterns The library offers a rich set of messaging patterns to suit different communication needs between microservices or between other components of a distributed system. This flexibility enables developers to select the most appropriate pattern for their specific use case, ranging from simple request-response models to complex sagas.
• Connection Management & Resilience MassTransit abstracts away connection management and exception handling, which provides a more resilient and stable messaging experience for applications. By doing so, it helps developers avoid common pitfalls associated with handling transient connection issues and broker downtimes.
• Developer-Centric Platform MassTransit is lauded for being developer-focused, offering a modern platform that prioritizes the ease of building reliable distributed applications. This streamlined development process accelerates the creation and maintenance of services and enhances overall code quality.

Examples of When to Use MassTransit:

• Event-Driven Systems: When building an event-driven system where different components react to events in real-time, MassTransit facilitates the efficient dispatching and handling of these events.
• Workflows & Long-running Processes: In scenarios that involve workflows or processes that span multiple services and require state management over time, MassTransit's support for sagas can be particularly useful.
• Load Balancing: For systems that must distribute workloads evenly across various workers to ensure scalability and reliability, MassTransit can effectively manage the distribution of messages to different service instances.
• Integrations & Third-party Extensions: Whenever there's a need to integrate with various message brokers or third-party extensions, MassTransit offers the extensibility required to facilitate these integrations without being locked into a specific technology.
• Decoupling Services: In projects where a clear separation of concerns is critical, and services should remain loosely coupled, MassTransit ensures that dependencies are minimized.

MassTransit is an amazing tool for the modern C# developer looking to build robust, scalable, and maintainable applications. Whether you're orchestrating a fleet of microservices or simply need a reliable way to communicate between distributed application components, MassTransit represents a strong choice that merits consideration, of course, you have more alternatives such as Wolverine, however, won't cover this one in this article.

Let's Start to work with MassTransit

You can download the demo project at https://github.com/ljscodex/NET8_MassTransitDemo

But if you want to implement MassTransit in your project, let me show you the basic steps:

You need to download the MassTransit Package from Nuget

Now, you need to let your App knows you want to use Masstransit so, let's go to the Program.CS file and add the following Line:

builder.Services.AddMassTransit( x=>
{
  x.AddConsumers(typeof(Program).Assembly);
  x.UsingInMemory (( context, cfg)  => 
        {
                cfg.ConfigureEndpoints(context);
        });
});        

Here we are telling the App we want to use MassTransit with InMemory Transport. here is where we have to change to UsingRabbitMQ, AmazonSQS, or AzureSB.

In this case, I used

 x.AddConsumers(typeof(Program).Assembly);        

it because I want to use all the Consumers on my App.

Now, we need to create a Contract to let the publisher and consumer know, which will be the Message Format.

In my case, I created a Person Record inside a MassTransitContract class

    public class MasstransitContracts
    {
        public record Person ()
        {
            public string Name { get; init; }
            public int Age {get; init;}
        };
    }        

After the Contract, we need to create a consumer, so let's create a Consumer Folder and add a new File (MasstransitDemoConsumer.cs)

namespace NET8_MassTransit_Demo.Consumers;

using System.Threading.Tasks;
using NET8_MassTransit_Demo.Contracts;
using MassTransit;
using Microsoft.Extensions.Logging;
using static NET8_MassTransit_Demo.Contracts.MasstransitContracts;

public class GettingStartedConsumer :
    IConsumer<Person>
{
    readonly ILogger<GettingStartedConsumer> _logger;

    public GettingStartedConsumer(ILogger<GettingStartedConsumer> logger)
    {
        _logger = logger;
    }

    public Task Consume(ConsumeContext<Person> context)
    {
        _logger.LogInformation($"Received Person: {context.Message.ToString()}");
        return Task.CompletedTask;
    }
}        

and now, we just need to start to use it.

In your Services/Repository add the IBus interface

        private readonly IBus _masstransitBus;

        public MassTransitDemoController( IBus masstransitBus)
        {
            _masstransitBus = masstransitBus;
        }        

YES, I used the controller (demo proposes) :P, but the idea is the same.

Now we can start to send messages from our methods, in my case I use the Get method in the controller to create the publisher.

        [HttpGet]
        public ActionResult<Person> Get([FromQuery]Person p)
        {
            _masstransitBus.Publish(p);
            return p;
        }        

Here is the magic, now, every time somebody consumes the Get endpoint, the consumers will receive a message with the Person information.

I hope this article was useful and if you have any trouble using it, just let me know!.