Microservices With Spring Boot - Part 5 - Using Eureka Naming Server

In this series, let's learn the basics of microservices and microservices architectures. We will also start looking at a basic implementation of a microservice with Spring Boot. We will create a couple of microservices and get them to talk to each other using Eureka Naming Server and Ribbon for Client Side Load Balancing.

This is part 5 of this series. In this part, we will focus on enabling Eureka Naming Server and have the microservices communicate with it.

Microservices with Spring Boot

• Part 1 - Getting Started with Microservices Architecture
• Part 2 - Creating Forex Microservice
• Part 3 - Creating Currency Conversion Microservice
• Part 4 - Using Ribbon for Load Balancing
• Current Part - Part 5 - Using Eureka Naming Server

You will learn:

• What is the need for a Naming Server?
• What is Eureka?
• How does a Naming Server enable location transparency between microservices?

Microservices Overview

In Parts 2 and 3, we created two microservices and established communication between them.

In Part 4, we used Ribbon to distribute load between the two instances of Forex Service. However, we are hardcoding the URLs of both instances of the Forex Service in CCS. That means that every time there is a new instance of FS, we would need to change the configuration of CCS. That's not cool.

In this part, we will use Eureka Naming Server to fix this problem.

Tools you will need:

• Maven 3.0+ is your build tool
• Your favorite IDE. We use Eclipse.
• JDK 1.8+

Complete Maven Project With Code Examples

Our GitHub repository has all the code examples.

Bootstrapping Eureka Naming Server With Spring Initializr

Creating a Eureka Naming Server with Spring Initializr is a cake walk. Spring Initializr is a great tool for bootstrapping your Spring Boot projects. You can create a wide variety of projects using Spring Initializr.

The following steps have to be done for a web services project:

• Launch Spring Initializr and choose the following:
  • Choose com.in28minutes.springboot.microservice.eureka.naming.server as Group
  • Choose spring-boot-microservice-eureka-naming-server as Artifact
  • Choose following dependencies
• Click Generate Project.
• Import the project into Eclipse. File -> Import -> Existing Maven Project.
• Do not forget to choose Eureka in the dependencies.

Enabling Eureka

EnableEurekaServer in SpringBootMicroserviceEurekaNamingServerApplication.

@SpringBootApplication
@EnableEurekaServer
public class SpringBootMicroserviceEurekaNamingServerApplication {

Configure the application name and port for the Eureka Server:

/spring-boot-microservice-eureka-naming-server/src/main/resources/application.properties

spring.application.name=netflix-eureka-naming-server
server.port=8761

eureka.client.register-with-eureka=false
eureka.client.fetch-registry=false

Launching Eureka Naming Server

Launch SpringBootMicroserviceEurekaNamingServerApplication as a Java application.

You can launch Eureka at http://localhost:8761

You will see that there are no instances connected to Eureka yet:

Connect FS and CCS Microservices With Eureka

Make these changes on both the microservices

Add to pom.xml:

    <dependency>
      <groupId>org.springframework.cloud</groupId>
      <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
    </dependency>

Configure Eureka URL in application.properties:

eureka.client.service-url.default-zone=http://localhost:8761/eureka

Restart all the instances of CCS and FS. You will see that the CCS and FS microservices are registered with Eureka Naming Server. That's cool!

This screenshot shows how to launch an additional instance of Forex Service on 8081.

You will see that one instance of CCS and two instances of FS microservices are registered with Eureka Naming Server.

Routing Ribbon Requests Through Eureka

All that you would need to do is to remove this configuration. Remove this configuration from application.properties:

forex-service.ribbon.listOfServers=localhost:8000,localhost:8001

Restart the CCS instance.

Eureka in Action

Currently, we have the following services up and running:

• Currency Conversion Microservice (CCS) on 8100
• Two instances of Forex Microservice on 8000 and 8001
• Eureka Server launched

Now you will see that the requests to CCS will be distributed between the two instances of the Forex Microservice by Ribbon through Eureka.

Request 1

GET to http://localhost:8100/currency-converter-feign/from/EUR/to/INR/quantity/10000

{
  id: 10002,
  from: "EUR",
  to: "INR",
  conversionMultiple: 75,
  quantity: 10000,
  totalCalculatedAmount: 750000,
  port: 8000,
}

Request 2

GET to http://localhost:8100/currency-converter-feign/from/EUR/to/INR/quantity/10000

{
  id: 10002,
  from: "EUR",
  to: "INR",
  conversionMultiple: 75,
  quantity: 10000,
  totalCalculatedAmount: 750000,
  port: 8001,
}

You can see that the port numbers in the two responses are different.

Exercise: Launch another instance of Forex Service on 8002. You will see that load gets automatically routed to it as well.

Cool! That's awesome, isn't it?

Summary

We have now created two microservices and established communication between them.

We are using Ribbon to distribute load between the two instances of Forex Service and Eureka as the naming server. When we launch new instances of Forex Service, you will see that load is automatically distributed to them.

The idea behind this series of five articles was to give the flavor of Spring Boot and Spring Cloud with microservices.

There is a lot more ground to cover with microservices. Until next time, cheers!

The complete code example for this project can be found in the GitHub repository.