Spring Cloud Netflix Eureka

In the previous tutorial, we have seen how to make REST API calls between multiple microservices.

In this tutorial, we will learn how to create a Service Registry using Spring Cloud Netflix Eureka in our Shopping cart Spring boot microservices project.

Service Registry and Discovery Overview

In microservices projects, Service Registry and Discovery play an important role because we most likely run multiple instances of services and we need a mechanism to call other services without hardcoding their hostnames or port numbers. In addition to that, in Cloud environments service instances may come up and go down anytime. So we need some automatic service registration and discovery mechanism.


Spring Cloud addresses this problem by providing Spring Cloud Netflix Eureka project to create a Service Registry and Discovery. 

In this tutorial, we will learn how to use SpringCloud Netflix Eureka for Service Registry and Discovery.

What we will build?

We can use Netflix Eureka Server to create a Service Registry and make our microservices (order-service, product-service, and payment-service) as Eureka Clients so that as soon as we start a microservice it will get registered with Eureka Server automatically with a logical Service ID. Then, the other microservices, which are also Eureka Clients, can use Service ID to invoke REST endpoints.

Prerequisites

Refer to the below tutorial to create three microservices such as order-serviceproduct-service, and payment-service.

Refer to the below tutorial to make REST API calls between multiple microservices:

1. Create and Setup Spring boot project in IntelliJ IDEA

Let us create a Service Registry using Netflix Eureka which is nothing but a SpringBoot application with a Eureka Server starter.
		<dependency>
			<groupId>org.springframework.cloud</groupId>
			<artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
		</dependency>

Let's create a Spring boot project using the spring initializr.

Refer to the below screenshot to enter details while creating the spring boot application using the spring initializr:

Click on Generate button to download the Spring boot project as a zip file. Unzip the zip file and import the Spring boot project in IntelliJ IDEA.

Here is the pom.xml file for your reference:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>2.7.4</version>
		<relativePath/> <!-- lookup parent from repository -->
	</parent>
	<groupId>com.microservices</groupId>
	<artifactId>service-registry</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<name>service-registry</name>
	<description>service-registry</description>
	<properties>
		<java.version>17</java.version>
		<spring-cloud.version>2021.0.4</spring-cloud.version>
	</properties>
	<dependencies>
		<dependency>
			<groupId>org.springframework.cloud</groupId>
			<artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
		</dependency>

		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-test</artifactId>
			<scope>test</scope>
		</dependency>
	</dependencies>
	<dependencyManagement>
		<dependencies>
			<dependency>
				<groupId>org.springframework.cloud</groupId>
				<artifactId>spring-cloud-dependencies</artifactId>
				<version>${spring-cloud.version}</version>
				<type>pom</type>
				<scope>import</scope>
			</dependency>
		</dependencies>
	</dependencyManagement>

	<build>
		<plugins>
			<plugin>
				<groupId>org.springframework.boot</groupId>
				<artifactId>spring-boot-maven-plugin</artifactId>
			</plugin>
		</plugins>
	</build>

</project>

2. Add @EnableEurekaServer annotation

We need to add @EnableEurekaServer annotation to make our SpringBoot application a Eureka Server-based Service Registry.

package net.javaguides.serviceregistry;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.server.EnableEurekaServer;

@SpringBootApplication
@EnableEurekaServer
public class ServiceRegistryApplication {

	public static void main(String[] args) {
		SpringApplication.run(ServiceRegistryApplication.class, args);
	}

}

3. Disable Eureka Server as Eureka Client

By default, each Eureka Server is also a Eureka client and needs at least one service URL to locate a peer. As we are going to have a single Eureka Server node (Standalone Mode), we are going to disable this client-side behavior by configuring the following properties in the application.yml file.

server:
  port: 8761

eureka:
  instance:
    hostname: localhost
  client:
    register-with-eureka: false
    fetch-registry: false

4. Registering Order-Service Microservice as Eureka Client

Let us make this order-service as a Eureka Client and register with the Eureka Server.

Add the Eureka Discovery starter to order-service:

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

Also, add the Spring cloud dependencies:

<dependencyManagement>
	<dependencies>
		<dependency>
			<groupId>org.springframework.cloud</groupId>
			<artifactId>spring-cloud-dependencies</artifactId>
			<version>${spring-cloud.version}</version>
			<type>pom</type>
			<scope>import</scope>
		</dependency>
	</dependencies>
</dependencyManagement>

Add version as property:

<properties>
	<java.version>17</java.version>
	<spring-cloud.version>2021.0.4</spring-cloud.version>
</properties

With spring-cloud-starter-netflix-eureka-client on the classpath, we just need to configure eureka.client.service-url.defaultZone property in application.yml to automatically register with the Eureka Server.

eureka:
  instance:
    prefer-ip-address: true
  client:
    fetch-registry: true
    register-with-eureka: true
    service-url:
      defaultZone: ${EUREKA_SERVER_ADDRESS:http://localhost:8761/eureka}

When a service is registered with Eureka Server it keeps sending heartbeats for certain intervals. If the Eureka server didn’t receive a heartbeat from any service instance it will assume the service instance is down and take it out of the pool.

5. Registering Product-Service Microservice as Eureka Client

Let us make this product-service as a Eureka Client and register with the Eureka Server.

Add the Eureka Discovery starter to product-service:

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

Also, add the Spring cloud dependencies:

<dependencyManagement>
	<dependencies>
		<dependency>
			<groupId>org.springframework.cloud</groupId>
			<artifactId>spring-cloud-dependencies</artifactId>
			<version>${spring-cloud.version}</version>
			<type>pom</type>
			<scope>import</scope>
		</dependency>
	</dependencies>
</dependencyManagement>

Add version as property:

<properties>
	<java.version>17</java.version>
	<spring-cloud.version>2021.0.4</spring-cloud.version>
</properties

With spring-cloud-starter-netflix-eureka-client on the classpath, we just need to configure eureka.client.service-url.defaultZone property in application.yml to automatically register with the Eureka Server.

eureka:
  instance:
    prefer-ip-address: true
  client:
    fetch-registry: true
    register-with-eureka: true
    service-url:
      defaultZone: ${EUREKA_SERVER_ADDRESS:http://localhost:8761/eureka}

When a service is registered with Eureka Server it keeps sending heartbeats for certain intervals. If the Eureka server didn’t receive a heartbeat from any service instance it will assume the service instance is down and take it out of the pool.

6. Registering Payment-Service Microservice as Eureka Client

Let us make this payment-service as a Eureka Client and register with the Eureka Server.

Let's open the pom.xml file of payment-service and add the Eureka Discovery starter  dependency:

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

Also, add the Spring cloud dependencies:

<dependencyManagement>
	<dependencies>
		<dependency>
			<groupId>org.springframework.cloud</groupId>
			<artifactId>spring-cloud-dependencies</artifactId>
			<version>${spring-cloud.version}</version>
			<type>pom</type>
			<scope>import</scope>
		</dependency>
	</dependencies>
</dependencyManagement>

Add version as property:

<properties>
	<java.version>17</java.version>
	<spring-cloud.version>2021.0.4</spring-cloud.version>
</properties

With spring-cloud-starter-netflix-eureka-client on the classpath, we just need to configure eureka.client.service-url.defaultZone property in application.yml to automatically register with the Eureka Server.

eureka:
  instance:
    prefer-ip-address: true
  client:
    fetch-registry: true
    register-with-eureka: true
    service-url:
      defaultZone: ${EUREKA_SERVER_ADDRESS:http://localhost:8761/eureka}

When a service is registered with Eureka Server it keeps sending heartbeats for certain intervals. If the Eureka server didn’t receive a heartbeat from any service instance it will assume the service instance is down and take it out of the pool.

7. Launch Eureka Server (Demo)

Netflix Eureka Service provides UI where we can see all the details about registered services.

Now run ServiceRegistryApplication and access http://localhost:8761 which will display the UI similar to the below screenshot.



Free Spring Boot Tutorial | Full In-depth Course | Learn Spring Boot in 10 Hours


Watch this course on YouTube at Spring Boot Tutorial | Fee 10 Hours Full Course

Comments