Eureka Yes. Netflix Developed, a REST-based component for service registration and discovery

It mainly includes two components: Eureka Server and Eureka Client.

• Eureka Client: A Java client used to simplify interaction with Eureka Server (usually the client and server in microservices)
• Eureka Server: The ability to provide service registration and discovery (usually a registry in a microservice)

Working structure diagram:

 

When each micro-service starts, it registers itself with Eureka Server via Eureka Client, which stores information about the service.

That is to say, every client and server of micro-service will register with Eureka Server, which leads to the topic of mutual recognition of micro-service.

• Synchronization: Each Eureka Server is also Eureka Client (logically)
  Synchronization of service registries between multiple Eureka Server s by replication forms high availability of Eureka
• Recognition: Eureka Client caches information in Eureka Server
  Even if all Eureka Server nodes are down, service consumers can still use the information in the cache to find service providers (I have personally observed)
• Renew: Microservices periodically (default 30s) send heartbeat information to Eureka Server (similar to heartbeat)
• Extension: Eureka Server performs a failure service detection function on a regular basis (default 60s)
  It checks for microservices that do not have Renew for more than a certain period of time (default 90s), and finds that the microservice node will be cancelled

Spring Cloud has integrated Eureka into its sub-project Spring Cloud Netflix

Eureka Server Integration in Spring Cloud

1.pom file configuration

<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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>

	<parent>
		<groupId>com.itmuch.cloud</groupId>
		<artifactId>microservice-spring-cloud</artifactId>
		<version>0.0.1-SNAPSHOT</version>
	</parent>

	<artifactId>microservice-discovery-eureka</artifactId>
	<packaging>jar</packaging>

	<properties>
		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
	</properties>

	<dependencies>
		<dependency>
			<groupId>org.springframework.cloud</groupId>
			<artifactId>spring-cloud-starter-eureka-server</artifactId>
		</dependency>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-security</artifactId>
		</dependency>
	</dependencies>

</project>

<dependencies>
Dependency ><! - eureka-server registration and discovery dependency
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-eureka-server</artifactId>
        </dependency>
Dependency ><! - eureka-server security management dependencies, such as username, password login - >
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-security</artifactId>
        </dependency>
    </dependencies>

2 yml configuration file

security:
  basic:
    enabled: true
  user:
    name: user
    password: password123
server:
  port: 8761
eureka:
  client:
    register-with-eureka: false
    fetch-registry: false
    service-url:
      defaultZone: http://user:password123@localhost:8761/eureka

3. boot class

package com.itmuch.cloud;

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

@SpringBootApplication
@EnableEurekaServer
public class EurekaApplication {
  public static void main(String[] args) {
    SpringApplication.run(EurekaApplication.class, args);
  }
}

Spring Cloud integrated Eureka client

1.pom file

<?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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>

	<artifactId>microservice-provider-user</artifactId>
	<packaging>jar</packaging>

	<name>microservice-provider-user</name>
	<description>Demo project for Spring Boot</description>

	<parent>
		<groupId>com.itmuch.cloud</groupId>
		<artifactId>microservice-spring-cloud</artifactId>
		<version>0.0.1-SNAPSHOT</version>
	</parent>

	<properties>
		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
		<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
		<java.version>1.8</java.version>
	</properties>

	<dependencies>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-data-jpa</artifactId>
		</dependency>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-web</artifactId>
		</dependency>
		<dependency>
			<groupId>com.h2database</groupId>
			<artifactId>h2</artifactId>
			<scope>runtime</scope>
		</dependency>

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

		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-actuator</artifactId>
		</dependency>
	</dependencies>

</project>

Dependency > <! - Client dependency - > Client dependency
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-eureka</artifactId>
        </dependency>

Dependency ><! - Operations and Maintenance Monitoring Browser View Dependency - > Dependency
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-actuator</artifactId>
        </dependency>

2.yml configuration file

server:
  port: 7900
spring:
  jpa:
    generate-ddl: false
    show-sql: true
    hibernate:
      ddl-auto: none
  datasource:
    platform: h2
    schema: classpath:schema.sql
    data: classpath:data.sql
  application:
    name: microservice-provider-user
logging:
  level:
    root: INFO
    org.hibernate: INFO
    org.hibernate.type.descriptor.sql.BasicBinder: TRACE
    org.hibernate.type.descriptor.sql.BasicExtractor: TRACE
    com.itmuch: DEBUG
eureka:
  client:
    healthcheck:
      enabled: true
    serviceUrl:
      defaultZone: http://user:password123@localhost:8761/eureka
  instance:
    prefer-ip-address: true
    instance-id: ${spring.application.name}:${spring.cloud.client.ipAddress}:${spring.application.instance_id:${server.port}}
    metadata-map:
      zone: ABC      # Ereka understandable metadata
      lilizhou: BBC  # Does not affect client behavior
    lease-renewal-interval-in-seconds: 5

3. Start the client class

package com.itmuch.cloud;

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

@SpringBootApplication
@EnableEurekaClient
public class MicroserviceSimpleProviderUserApplication {

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