spring boot 2.0.3+spring cloud （Finchley）1、搭建服務注冊和發現組件Eureka 以及構建高可用Eureka Server集群

一 、搭建Eureka

編寫Eureka Server

由於有多個spring boot項目，采用maven多module的結構，項目結構如下：

新建一個maven主工程，在主maven的pom文件中引入spring boot和spring cloud的依賴

<?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.cralor</groupId>
    <artifactId>chap5-2-eureka</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>pom</packaging>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.0.3.RELEASE</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.RELEASE</spring-cloud.version>
    </properties>

    <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>

    <!--使用aliyun鏡像-->
    <repositories>
        <repository>
            <id>alimaven</id>
            <name>Maven Aliyun Mirror</name>
            <url>http://maven.aliyun.com/nexus/content/repositories/central/</url>
            <releases>
                <enabled>true</enabled>
            </releases>
            <snapshots>
                <enabled>false</enabled>
            </snapshots>
        </repository>
    </repositories>

</project>

采用spring initializr 方式新建module工程eureka-server，作為服務注冊中心。在pom文件中引入相關依賴包括繼承主maven工程的pom文件，eureka server的起步依賴spring-cloud-starter-netflix-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.cralor</groupId>
    <artifactId>eureka-server</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>

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

    <parent>
        <groupId>com.cralor</groupId>
        <artifactId>chap5-2-eureka</artifactId>
        <version>0.0.1-SNAPSHOT</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>
    </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>

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

</project>

在配置文件application.yml中做相關配置，指定eureka server 的端口號為8761，默認eureka server會向自己注冊，需要配置eureka.client.registerWithEureka和eureka.client.fetchRegistry為false，防止自己注冊自己。

server:
  port: 8761
eureka:
  instance:
    hostname: localhost
  client:
    register-with-eureka: false
    fetch-registry: false
    serviceUrl:
      defaultZone: http://${eureka.instance.hostname}:${server.port}/eureka/

在工程啟動類加上注解@EnableEurekaServer，開啟eureka server功能

@EnableEurekaServer
@SpringBootApplication
public class EurekaServerApplication {

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

啟動程序，在瀏覽器訪問eureka server 主界面http://localhost:8761，在上面的Instance currently registered with Eureka這一項還沒有注冊任何實例，因為還沒有eureka client 客戶端向注冊中心注冊服務。

 

編寫Eureka Client

 新建module工程eureka-client，該工程作為Eureka Client的工程會向服務注冊中心Eureka Server注冊。在pom文件引入相關依賴包括eureka client起步依賴spring-cloud-starter-netflix-eureka-client

<?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.cralor</groupId>
    <artifactId>eureka-client</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>

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

    <parent>
        <groupId>com.cralor</groupId>
        <artifactId>chap5-2-eureka</artifactId>
        <version>0.0.1-SNAPSHOT</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>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>

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

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

</project>

在配置文件中做相關配置，程序名為eureka-client，端口號8762，服務注冊地址為http://localhost:8761/eureka/。

server:
  port: 8762
spring:
  application:
    name: eureka-client
eureka:
  client:
    serviceUrl:
      defaultZone: http://localhost:8761/eureka/

啟動類保持默認生成的即可， Finchley 這個版本的 Spring Cloud 已經無需添加@EnableDiscoveryClient注解了。（那么如果我引入了相關的 jar 包又想禁用服務注冊與發現怎么辦？設置eureka.client.enabled=false）

@EnableDiscoveryClient is no longer required. You can put a DiscoveryClient implementation on the classpath to cause the Spring Boot application to register with the service discovery server.
Spring Cloud - @EnableDiscoveryClient

@SpringBootApplication
public class EurekaClientApplication {

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

啟動eureka client工程，成功后會在控制台打印

:DiscoveryClient_EUREKA-CLIENT/DESKTOP-R9RM7VT:eureka-client:8762: registering service...
DiscoveryClient_EUREKA-CLIENT/DESKTOP-R9RM7VT:eureka-client:8762 - registration status: 204

說明eureka client已向eureka server注冊了，訪問http://localhost:8761，顯示已有一個實例注冊

 

 二、構建高可用Eureka Server集群

1、在實際項目中，一個注冊中心遠遠無法滿足實際的生產環境，我們需要多個注冊中心進行集群，達到真正的高可用。

首先更改eureka-server的配置文件application.yml，采用多配置文件格式，在啟動時指定具體的配置文件

spring:
  profiles:
    active: native
  application:
    name: peer-cluster

application-peer1.yml

server:
  port: 8761
eureka:
  instance:
    hostname: peer1
  client:
    serviceUrl:
      defaultZone: http://peer2:8762/eureka/

application-peer2.yml

server:
  port: 8762
eureka:
  instance:
    hostname: peer2
  client:
    serviceUrl:
      defaultZone: http://peer1:8761/eureka/

定義了兩個配置文件peer1和peer2，hostname分別是peer1和peer2，並且在application.yml定義了相同的實例名稱peer-cluster。peer1的注冊地址為http://peer2:8762/eureka/，peer2的注冊地址為http://peer1:8761/eureka/，讓它們互相注冊，以達到同步的目的。

因為是在本地搭建eureka server集群，需要修改本地的host。Windows在C:\Windows\System32\drivers\etc\hosts中修改，mac電腦通過終端vim/etc/hosts進行編輯修改，修改如下：

127.0.0.1 peer1

127.0.0.1 peer2

使用maven的package命令生成eureka server的jar包，在target目錄下會生成eureka-server-0.0.1-SNAPSHOT.jar。通過java -jar的方式分別啟動peer1和peer2，命令如下：

java -jar eureka-server-0.0.1-SNAPSHOT.jar --spring.profiles.active=peer1
java -jar eureka-server-0.0.1-SNAPSHOT.jar --spring.profiles.active=peer2

訪問http://peer1:8761和http://peer2:8762如圖

 

 

 可以看到peer1和peer2分別為對方的實例並且registered-replicas和available-replicas分別有了對方的地址

2、修改eureka-client的配置文件

server:
  port: 8763
spring:
  application:
    name: eureka-client
eureka:
  client:
    serviceUrl:
      defaultZone: http://peer1:8761/eureka

此時eureka-client的配置文件並沒有指定向peer2的節點eureka server注冊，訪問peer2主界面http://peer2:8762/eureka。節點peer2的主界面顯示eureka client已向peer2注冊，可見peer1的注冊信息列表已經同步到了peer2節點，這是因為eureka是通過在各個節點進行復制來達到高可用的目的。

 

 

 

ps：關於spring cloud組件的這幾篇隨筆文章是在我學習方志朋老師的《深入理解Spring Cloud與微服務構建》一書的過程中寫的。微信號：walkingstory。

 寫的非常好的文章：https://windmt.com/2018/04/14/spring-cloud-1-services-governance/

　　https://windmt.com/

 

案例代碼地址：https://github.com/cralor7/springcloud