SpringCloud-Service Registration and Discovery (Eureka)

Eureka Server

<?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>

	<groupId>com.imooc</groupId>
	<artifactId>eureka</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<packaging>jar</packaging>

	<name>eureka</name>
	<description>Demo project for Spring Boot</description>

	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>2.0.0.M3</version>
		<relativePath/> <!-- lookup parent from repository -->
	</parent>

	<properties>
		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
		<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
		<java.version>1.8</java.version>
		<spring-cloud.version>Finchley.M2</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>

	<repositories>
		<repository>
			<id>spring-snapshots</id>
			<name>Spring Snapshots</name>
			<url>https://repo.spring.io/snapshot</url>
			<snapshots>
				<enabled>true</enabled>
			</snapshots>
		</repository>
		<repository>
			<id>spring-milestones</id>
			<name>Spring Milestones</name>
			<url>https://repo.spring.io/milestone</url>
			<snapshots>
				<enabled>false</enabled>
			</snapshots>
		</repository>
	</repositories>

	<pluginRepositories>
		<pluginRepository>
			<id>spring-snapshots</id>
			<name>Spring Snapshots</name>
			<url>https://repo.spring.io/snapshot</url>
			<snapshots>
				<enabled>true</enabled>
			</snapshots>
		</pluginRepository>
		<pluginRepository>
			<id>spring-milestones</id>
			<name>Spring Milestones</name>
			<url>https://repo.spring.io/milestone</url>
			<snapshots>
				<enabled>false</enabled>
			</snapshots>
		</pluginRepository>
	</pluginRepositories>

</project>

eureka:
  client:
    service-url:
      defaultZone: http://localhost:8761/eureka/
    register-with-eureka: false
  server:
    # 如果在开发模式下不希望一会上线一会下线的客户端被认为是在线。那就这样设置。
    # 是要在服务中心的配置里面写在application.yml，eureka.server.enable-self-preservation:false配置注意只能在开发环境把它关闭，生成环境不要关闭了一定要打开，方便做微服务的调用，不会出现错误
    enable-self-preservation: false
spring:
  application:
    name: eureka
server:
  port: 8761

package com.imooc.eureka;

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);
	}
}

Start in the background: nohup java -jar xx.jar> / dev / null 2> & 1 & where 2 represents an error and 1 represents standard output: 2> & 1 is to redirect the error output behavior to standard output and / dev / null represents garbage Bucket, & means running in the background, nohup means the terminal is closed and does not hang up. Overall understanding of the program: make the program run in the background without saving the output file (standard error is redirected to standard output, and standard output is redirected to / dev / null, ie do not save)

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Eureka Client

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<?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>

	<groupId>com.imooc</groupId>
	<artifactId>client</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<packaging>jar</packaging>

	<name>client</name>
	<description>Demo project for Spring Boot</description>

	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>2.0.0.M3</version>
		<relativePath/> <!-- lookup parent from repository -->
	</parent>

	<properties>
		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
		<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
		<java.version>1.8</java.version>
		<spring-cloud.version>Finchley.M2</spring-cloud.version>
	</properties>

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

	<repositories>
		<repository>
			<id>spring-snapshots</id>
			<name>Spring Snapshots</name>
			<url>https://repo.spring.io/snapshot</url>
			<snapshots>
				<enabled>true</enabled>
			</snapshots>
		</repository>
		<repository>
			<id>spring-milestones</id>
			<name>Spring Milestones</name>
			<url>https://repo.spring.io/milestone</url>
			<snapshots>
				<enabled>false</enabled>
			</snapshots>
		</repository>
	</repositories>

	<pluginRepositories>
		<pluginRepository>
			<id>spring-snapshots</id>
			<name>Spring Snapshots</name>
			<url>https://repo.spring.io/snapshot</url>
			<snapshots>
				<enabled>true</enabled>
			</snapshots>
		</pluginRepository>
		<pluginRepository>
			<id>spring-milestones</id>
			<name>Spring Milestones</name>
			<url>https://repo.spring.io/milestone</url>
			<snapshots>
				<enabled>false</enabled>
			</snapshots>
		</pluginRepository>
	</pluginRepositories>

</project>

eureka:
  client:
    service-url:
      defaultZone: http://localhost:8761/eureka/
#  instance:
#    hostname: clientName
spring:
  application:
    name: client

package com.imooc.client;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;

@SpringBootApplication
@EnableDiscoveryClient
public class ClientApplication {

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

High availability

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Here are three high can be used as an example

Eureka Server 1

eureka:
  client:
    service-url:
      defaultZone: http://localhost:8762/eureka/, http://localhost:8763/eureka/
    register-with-eureka: false
  server:
    enable-self-preservation: false
spring:
  application:
    name: eureka
server:
  port: 8761

Eureka Server 2

eureka:
  client:
    service-url:
      defaultZone: http://localhost:8761/eureka/, http://localhost:8763/eureka/
    register-with-eureka: false
  server:
    enable-self-preservation: false
spring:
  application:
    name: eureka
server:
  port: 8762

Eureka Server 3

eureka:
  client:
    service-url:
      defaultZone: http://localhost:8761/eureka/, http://localhost:8762/eureka/
    register-with-eureka: false
  server:
    enable-self-preservation: false
spring:
  application:
    name: eureka
server:
  port: 8763

Eureka Client

eureka:
  client:
    service-url:
      defaultZone: http://localhost:8761/eureka/, http://localhost:8762/eureka/, http://localhost:8763/eureka/
#  instance:
#    hostname: clientName
spring:
  application:
    name: client

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Attached

I have repeatedly thought about why service discovery is needed in distributed systems. Later, I also found the answer online. Now A is one and B is multi-node (ie cluster). How does A go to find B, then it is to write matches one by one, one by one. However, since there are not only many B, it may also change dynamically. It is not good to write B's IP address into A, because the address may be less or it may change. Now, there is a registration center that will automatically register up.

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