In a previous article, we learnt all about Microservice Architecture in ASP.NET Core (I recommend reading this before continuing), API Gateways, Ocelot Configuration and much more. In this article, let’s talk about another aspect – Microservice Communication using RabbitMQ with ASP.NET Core. Essentially, we will learn how to enable communication between Microservices using RabbitMQ and MassTransit. Let’s get started!

Table of Contents

• What is RabbitMQ?
• Advantages of RabbitMQ
• What we will build?
• Setting up the Environment
• Installing ErLang
• Installing RabbitMQ as a Service in Windows
• Enabling RabbitMQ Management Plugin – Dashboard
• Getting Started – RabbitMQ with ASP.NET Core
• Shared Model Library
• Setting up the the Publisher Microservice
• Installing the Required MassTransit Packages
• What is MassTransit?
• Configuring MassTrasit
• Setting up the the Consumer Microservice
• Testing the Microservice
• Scenario #1 – When the Consumer is Online
• Scenario #2 – Consumer is Offline. Back Online after N Minutes
• Summary

What is RabbitMQ?

RabbitMQ is one of the most popular Message-Broker Service. It supports various messaging protocols. It basically gives your applications a common platform for sending and receiving messages. This ensures that your messages (data) is never lost and is successfully received by each intended consumer. RabbitMQ makes the entire process seemless.

In simple words, you will have a publisher that publishes messages to the message broker (RabbitMQ Server). Now the server stores the message in a queue. To this particular queue , multiple consumers can subscribe. Whenever there is a new message, each of the subscibers would receive it. An application can act as both producer / consumer based on how you configure it and what the requirement demands.

A message could consist of any kind of information like a simple string to a complex nested class. RabbitMQ stores these data within the server till a consumer connects and take the message off the queue for processing.

Additional, RabbitMQ provides a cool Dashboard for monitoring the messages and queues. We will be setting up this too later in this article!

Advantages of RabbitMQ

There are quite a lot of advantages of using a queue based messaging solution rather that directly sending messages to the intendend consumer. Here are few of the advantages.

1. Better Scalability – Now, you will not have to depend on just one VM / processor / server to process your request. When it get’s to the point where you first server finds it tough to process the incoming queue data, you can simply add another server that can share the load and improve the overall response time. This is quite easy with the queue concept in RabbitMQ.
2. Clean User Experience – You users are less likely to see any errors, thanks to the microservice based message broker architecture.
3. **Higher availability **– Even if the main Microservice is down to a technical glitch on on-going update, the messages are never lost. It gets stored to the RabbitMQ server. Once the Service comes online, it consumes the pending messages and processes it.

Here is a simple demonstration of work-flow in a basic RabbitMQ setup. Here consumer #3 is offline for a specific time. This does not in any way affect the integrity of the system. Even if all the consumers are offline, the messages are still in RabbitMQ waiting for the consumers to come online and take the message off their particular queues.

#asp.net core #microservices