SpringCloud學習筆記:服務註冊與發現Eureka(2)

libingql發表於2018-04-14

1. Eureka簡介

  Eureka是一個用於服務註冊和發現的元件,分為Eureka Server和Eureka Client,Eureka Server為Eureka服務註冊中心,Eureka Client為Eureka客戶端。

  Eureka是SpringCloud首選推薦的註冊與服務發現元件,與SpringCloud其他元件可以無縫對接。

  Eureka的基本框架主要包括3種角色:

  ◊ Register Service:服務註冊中心,是一個Eureka Server,提供服務註冊與發現功能;

  ◊ Provider Service:服務提供者,是一個Eureka Client,提供服務;

  ◊ Consumer Service:服務消費者,是一個Eureka Client,消費服務。

  服務消費基本過程:

  (1)首先需要一個服務註冊中心Eureka Server;

  (2)服務提供者Eureka Client向服務註冊中心Eureka Server註冊,將自己的資訊(服務名、服務IP地址)通過REST API的形式提交註冊週年更新Eureka Server;

  (3)服務消費者Eureka Client向服務註冊中心Eureka Server註冊,服務消費者獲取服務註冊列表資訊。該列表資訊包含所有向服務註冊中心Eureka Server註冊的服務資訊;

  (4)服務消費者Eureka Client獲取服務註冊列表資訊之後,獲得服務提供者的IP地址,通過HTTP遠端排程來消費服務提供者的服務。

2. Eureka示例專案

  專案結構:採用Maven多Module結構

  

  主Maven專案pom.xml:

<?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>libing</groupId>
    <artifactId>libing-eureka</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>pom</packaging>

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

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.0.1.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.M9</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>

    <modules>
        <module>eureka-server</module>
        <module>eureka-client</module>
    </modules>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <optional>true</optional>
        </dependency>
    </dependencies>

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

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

</project>
pom.xml

2.1 Eureka Server

  Eureka Server依賴項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>priv.libing</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>libing</groupId>
        <artifactId>libing-eureka</artifactId>
        <version>0.0.1-SNAPSHOT</version>
    </parent>

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

</project>
pom.xml

  application.yml:

server:
  port: 8761
eureka:
  instance:
    hostname: localhost
  client:
    fetch-registry: false            # 禁用向自己註冊
    register-with-eureka: false      # 只維護例項,不去檢索服務
    service-url:
      default-zone: http://${eureka.instance.hostname}:${server.port}/eureka/

  注:預設Eureka Server會向自己註冊

  EurekaServerApplication.java:

package priv.libing.eurekaserver;

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

@EnableEurekaServer
@SpringBootApplication
public class EurekaServerApplication {

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

}

  其中:註解@EnableEurekaServer開啟Eureka Server功能。

  啟動程式,在瀏覽器中訪問Eureka主介面 http://localhost:8761/

2.2 Eureka Client

  Eureka Client引用項:

    ◊ spring-cloud-starter-netflix-eureka-client

    ◊ spring-boot-starter-web

<?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>priv.libing</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>libing</groupId>
        <artifactId>libing-eureka</artifactId>
        <version>0.0.1-SNAPSHOT</version>
    </parent>

    <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-web</artifactId>
        </dependency>
    </dependencies>

</project>
pom.xml

  application.yml:

eureka:
  client:
    service-url:
      default-zone: http://locahost:8761/eureka/
server:
  port: 8762
spring:
  application:
    name: eureka-client

  EurekaClientApplication.java:

package priv.libing.eurekaclient;

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

@EnableEurekaClient
@SpringBootApplication
public class EurekaClientApplication {

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

  其中,註解@EnableEurekaClient開啟Eureka Client功能。

  啟動執行eureka-server及eureka-client:

  以上示例程式碼:libing-eureka.zip

3. Eureka Server叢集

  在實際專案中,微服務例項較多,需要對Eureka Server進行高可用叢集。

  本地搭建Eureka Server叢集,修改C:\Windows\System32\drivers\etc\hosts

127.0.0.1       slave1
127.0.0.1       slave2

  eureka-server調整結構:

  

  application.yml:

spring:
  application:
    name: eureka-server

  application-slave1.yml:

server:
  port: 8761
eureka:
  instance:
    hostname: slave1
  client:
    service-url:
      default-zone: http://slave2:8762/eureka/

  application-slave2.yml:

server:
  port: 8762
eureka:
  instance:
    hostname: slave2
  client:
    service-url:
      default-zone: http://slave1:8761/eureka/

  eureka-client專案application.yml:

eureka:
  client:
    service-url:
      default-zone: http://slave1:8761/eureka/, http://slave2:8762/eureka/
server:
  port: 8763
spring:
  application:
    name: eureka-client

  (1)eureka-server執行:mvn:package

java -jar F:\eureka-server-0.0.1-SNAPSHOT.jar --spring.profiles.active=slave1
java -jar F:\eureka-server-0.0.1-SNAPSHOT.jar --spring.profiles.active=slave2

  (2)eureka-server執行:IDEA配置一個專案多例項

  

  Single instance only:取消勾選

  Active profiles:slave1或slave2,分別配置,執行兩個例項。

  以上示例程式碼:libing-eureka-slave.zip

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