Microservices Communication with RabbitMQ

Microservices are popular because they are flexible and can handle a lot. But getting them to talk to each other smoothly is a big challenge. RabbitMQ helps with that. It's like a go-between, making sure different services can chat without any problems. In this article, we'll see how RabbitMQ makes it easy for microservices to communicate in a big system.

Think of RabbitMQ as a helpful messenger. It follows some rules to make sure messages get from one service to another. It sits in the middle, helping out the services that send messages (producers) and the ones that get them (consumers). RabbitMQ has three main parts: Exchanges, Queues, and Bindings. They work together to make sure messages go where they're supposed to without any issues.

Key Terminologies:

• Message Broker: A middleman that manages messages between applications.
• Message Queue: A temporary storage where messages wait for processing.
• Exchange: Routes messages from producers to queues based on predefined rules.
• Queue: Stores messages until they're consumed by consumers.
• Binding: Defines how messages are routed from exchanges to queues.
• Producer: Generates and sends messages to RabbitMQ.
• Consumer: Receives and processes messages from RabbitMQ.
• Routing Key: Determines which queues receive messages based on exchange rules.
• AMQP: A messaging protocol defining message exchange formats and rules.
• Dead Letter Exchange (DLX): Receives undeliverable messages from queues.
• Publisher-Subscriber Pattern: Publishers send messages to an exchange, and subscribers receive them from bound queues.
• Remote Procedure Call (RPC): Clients send requests to servers and wait for responses.

Implementation of the Microservices Communication with RabbitMQ

Below is the implementation of the Microservices Communication with RabbitMQ.

Set up the RabbitMQ

We can download RabbitMQ using this link after that, install and run RabbitMQ locally on the computer system.

Run the RabbitMQ:

rabbitmq-plugins.bat enable rabbitmq_management

Refer the below cmd plugins:

👁 Plugins

Once the above command is run, RabbitMQ will be running on the local system at port number 15672. The default username and password are "guest."

👁 RabbitMQ login page

Create the Producer-service

Below are the steps to create the producer service.

Step 1: Create a new Spring Boot project using Spring Initializr, and include the following dependencies:

• Spring Web
• Spring for RabbitMQ
• Lombok

Once the project is created, the file structure will resemble the image below.

👁 Producer Service Folder Structure

Step 2:

Open the application.properties file and add the RabbitMQ connection properties to the project.

spring.application.name=producer-service

# RabbitMQ Config
spring.rabbitmq.host=localhost
spring.rabbitmq.port=5672
spring.rabbitmq.username=guest
spring.rabbitmq.password=guest
spring.rabbitmq.queue=my-queue
spring.rabbitmq.exchange=my-exchange
spring.rabbitmq.routingkey=my-routingkey

spring.main.allow-bean-definition-overriding=true

Step 3: Create theMessage class

We'll create the model class for the message entity of the producer service.

Go to src > org.example.produceservice> model > Message and put the below code.

Step 4: Create the RabbitMQ Configuration class

We'll create the configuration class to configure RabbitMQ.

Go to src > org.example.produceservice> config > RabbitMQ and put the below code.

Step 5: Create the Message Controller class

We'll create the controller class to send messages to the consumer service.

Go to src > org.example.produceservice> controller > MessageController and put the below code.

Step 6: Open the Main Class and insert the following code.

Go to src > org.example.produceservice > ProduceServiceApplication and put the below code.

Step 7: Run the application

Once we run the application, then the project will run at port 8080.

👁 Project Runs

Create the Consumer Service

Below are the steps to create the consumer service.

Step 1: Create the Spring Boot Project

Create a new Spring Boot project using Spring Initializr, and include the following dependencies:

• Spring Web
• Spring for RabbitMQ
• Lombok
• Spring Devtools

Once the project is created, the file structure will resemble the image below.

👁 Consumer-Service Project Structure

Step 2: Configure the RabbitMQ Connection

Open the application.properties file and add the RabbitMQ connection properties to the project.

spring.application.name=consumer-service

server.port=8081

# RabbitMQ Config
spring.rabbitmq.host=localhost
spring.rabbitmq.port=5672
spring.rabbitmq.username=guest
spring.rabbitmq.password=guest
spring.rabbitmq.queue=my-queue
spring.rabbitmq.exchange=my-exchange
spring.rabbitmq.routingkey=my-routingkey

Step 3: Create the RabbitMQ Configuration class

We'll create the configuration class to configure RabbitMQ.

Go to src > org.example.consumerservice> config > RabbitMQ and put the below code.

Step 4: Create the Listener class

We will create the Listener class to configure RabbitMQ.

Go to src > org.example.consumerservice> listener > MessageListener and put the below code.

Step 5: Open the Main class and insert the following code.

Go to src > org.example.consumerservice > ConsumerServiceApplication and put the below code.

Step 6: Run the application

Once we run the application, the project will run on port 8081. We can observe the messages being sent and received in the console.

👁 Project Runs

Endpoint API:

POST http://localhost:8080/send

JSON Body:

{
 "content": "Hello RabbitMQ",
 "sender:" : "producer-service:
}

Output:

👁 Message sent by Producer Service

Consumer-service receive the message:

👁 Consumer-service receive the message

This example demonstrates setting up a producer service that sends messages to RabbitMQ and a consumer service that listens for messages from RabbitMQ.