Do you use MassTransit to build reliable distributed applications?

<introEmbed body={<> When building distributed applications messaging is a common pattern to use. Often we might take a hard dependency on a specific messaging technology, such as Azure Service Bus or RabbitMQ. This can make it difficult to change messaging technologies in the future. Good architecture is about making decisions that make things easy to change in future. This is where MassTransit comes in. [MassTransit](https://masstransit.io/) is a popular open-source .NET library that makes it easy to build distributed applications using messaging without tying you to one specific messaging technology. </>} />

.NET Messaging Libraries

There are several .NET messaging libraries that all abstract the underlying transport. These include:

• MassTransit (recommended)
• NServiceBus
• Rebus

There are also the service bus specific libraries:

• Azure Service Bus(not recommended)
• Amazon SQS(not recommended)
• RabbitMQ(not recommended)
• (and more)

Advantages of using MassTransit

✅ Open-source and free to use

✅ Enables swapping of messaging transports by providing a common abstraction layer

✅ Supports multiple messaging concepts:

• Point-to-Point
• Publish/Subscribe
• Request/Response

✅ Supports multiple messaging transports:

• In-Memory
• RabbitMQ
• Azure Service Bus
• Amazon SQS
• ActiveMQ
• Kafka
• gRPC
• SQL/DB

✅ Supports complex messaging patterns such as Sagas

Scenarios

Scenario 1 - Modular Monolith

A Modular Monolith architecture requires all modules to be running in a single process. MassTransit can be used to facilitate in-memory communication between modules in the same process.

This allows us to send events between modules and also request data from other modules.

Scenario 2 - Azure Hosted Microservices

When building microservices in Azure, it's common to use Azure Service Bus as the messaging transport. With minimal changes, MassTransit can be used to send messages to and from Azure Service Bus instead of using the In-Memory transport.

Scenario 3 - Locally Developing Microservices

When developing microservices locally, it's common to use containers for each service. However, some of the cloud based messaging services (e.g. Azure Service Bus) are not able to be run in a container locally. In this scenario, we can easily switch from using the Azure Service Bus transport to Containerized RabbitMQ transport

Demo Code

If you're interested in seeing MassTransit in action, check out github.com/danielmackay/dotnet-mass-transit