Eureka服务中心的搭建(2)

朱雀 2021-01-18 13:42 544阅读 0赞

# 注册中心高可用 #

理论上来讲，服务消费者本地缓存了服务提供者的地址。即使 Eureka Server 宕机，也不会影响服务之间的调用，但是一旦涉及到服务的上下线，本地的缓存信息将会出现偏差，从而影响到了整个微服务架构的稳定性，因此搭建 Eureka Server 集群来提高整个架构的高可用性，是非常有必要的。这样就可以使注册中心高可用。

# 搭建Eureka集群 #

开启 Eureka 集群配置后，服务启动时 Eureka Server 会将注册信息向其它 Eureka Server 进行同步，因此搭建高可用架构只需要将 Eureke Server 配置指向其它可用的 serviceUrl 即可。

我们在上面 Eureka 单个示例的基础上，复制出三份来分别命名为：eureka-a、eureka-b、eureka-c 三个示例项目，使用这三个示例项目搭建 Eureka Server 的集群。

接下来需要分别修改 eureka-a、eureka-b、eureka-c 的配置信息。

eureka-a的配置信息如下

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

spring:
      application:
        name: eureka server
    server:
      port: 8001
    
    eureka:
      instance:
        hostname: eurekaA
      client:
        serviceUrl.defaultZone: http://eurekaB:8002/eureka/,http://eurekaC:8003/eureka/
        register-with-eureka: true
        fetch-registry: true

完整的pom.xml如下

<?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>
        <parent>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-parent</artifactId>
            <version>2.1.6.RELEASE</version>
            <relativePath/> 
        </parent>
        <groupId>cn.com.scitc</groupId>
        <artifactId>eureka-a</artifactId>
        <version>0.0.1-SNAPSHOT</version>
        <name>eureka-a</name>
        <description>Demo project for Spring Boot</description>
    
        <properties>
            <java.version>1.8</java.version>
            <spring-cloud-version>Greenwich.SR1</spring-cloud-version>
        </properties>
    
        <dependencies>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-web</artifactId>
            </dependency>
    
            <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>

eureka-b的配置信息如下:

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

spring:
      application:
        name: eureka server
    server:
      port: 8002
    
    eureka:
      instance:
        hostname: eurekaB
      client:
        serviceUrl.defaultZone: http://eurekaA:8001/eureka/,http://eurekaC:8003/eureka/
        register-with-eureka: true
        fetch-registry: true

完整的pom.xml如下

<?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>
        <parent>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-parent</artifactId>
            <version>2.1.6.RELEASE</version>
            <relativePath/> 
        </parent>
        <groupId>cn.com.scitc</groupId>
        <artifactId>eureka-b</artifactId>
        <version>0.0.1-SNAPSHOT</version>
        <name>eureka-b</name>
        <description>Demo project for Spring Boot</description>
    
        <properties>
            <java.version>1.8</java.version>
            <spring.cloud.version>Greenwich.SR1</spring.cloud.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-server</artifactId>
            </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>

eureka-c的配置信息如下:

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

spring:
      application:
        name: eureka server
    server:
      port: 8003
    
    eureka:
      instance:
        hostname: eurekaC
      client:
        serviceUrl.defaultZone: http://eurekaA:8001/eureka/,http://eurekaB:8002/eureka/
        register-with-eureka: true
        fetch-registry: true

<?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>
        <parent>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-parent</artifactId>
            <version>2.1.6.RELEASE</version>
            <relativePath/> 
        </parent>
        <groupId>cn.com.scitc</groupId>
        <artifactId>eureka-c</artifactId>
        <version>0.0.1-SNAPSHOT</version>
        <name>eureka-c</name>
        <description>Demo project for Spring Boot</description>
    
        <properties>
            <java.version>1.8</java.version>
            <spring.cloud.version>Greenwich.SR1</spring.cloud.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-server</artifactId>
            </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>

eureka.client.register-with-eureka和eureka.client.fetch-registry配置为 true ，表示将自己注册到注册中心，并且从注册中心获取注册信息

eureka.client.serviceUrl.defaultZone，指向其它两个注册中心，重点配置内容

# 测试 #

依次启动 eureka-a、eureka-b、eureka-c 项目，等待全部启动完成之后，浏览器访问地址：localhost:8001  
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# 总结 #

我们学习了为什么需要使用注册中心，以及 Eureka 作为注册中心最关键的组件，都有哪些特点和优势。

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