Spring Cloud 之Eureka高可用

约定不等于承诺〃 2022-12-15 02:51 145阅读 0赞

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## Spring Cloud 之Eureka高可用 ##

我这里就使用三个Eureka Server和一个Eureka Client来演示Eureka高可用，架构图如下：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM3OTYwNjAz_size_16_color_FFFFFF_t_70]

可以把这三个Eureka Server看成跨区域的注册中心（比如北京、上海、深圳）。

创建第一个Spring Boot项目作为Eureka Server1。  
`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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
        <modelVersion>4.0.0</modelVersion>
    
        <groupId>com.kaven</groupId>
        <artifactId>eureka</artifactId>
        <version>0.0.1-SNAPSHOT</version>
    
        <name>eureka</name>
        <description>Demo project for Spring Boot</description>
    
        <parent>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-parent</artifactId>
            <version>2.0.6.RELEASE</version>
            <relativePath/> 
        </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.SR2</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>
    </project>

`application.yml`如下：

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

启动类：

package com.kaven.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);
        }
    }

注解`@EnableEurekaServer`不要忘记加上。

创建第二个Spring Boot项目作为Eureka Server2。  
`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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
        <modelVersion>4.0.0</modelVersion>
    
        <groupId>com.kaven</groupId>
        <artifactId>eureka1</artifactId>
        <version>0.0.1-SNAPSHOT</version>
    
        <name>eureka1</name>
        <description>Demo project for Spring Boot</description>
    
        <parent>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-parent</artifactId>
            <version>2.0.6.RELEASE</version>
            <relativePath/> 
        </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.SR2</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>
    </project>

`application.yml`如下：

eureka:
      client:
        service-url:
          defaultZone: http://localhost:8761/eureka/,http://localhost:8763/eureka/
        register-with-eureka: true
      server:
        enable-self-preservation: true
    
    spring:
      application:
        name: eureka1
    
    server:
      port: 8762

启动类：

package com.kaven.eureka;
    
    import org.springframework.boot.SpringApplication;
    import org.springframework.boot.autoconfigure.SpringBootApplication;
    import org.springframework.cloud.netflix.eureka.server.EnableEurekaServer;
    
    @SpringBootApplication
    @EnableEurekaServer
    public class Eureka1Application { 
    
        public static void main(String[] args) { 
            SpringApplication.run(Eureka1Application.class, args);
        }
    }

创建第三个Spring Boot项目作为Eureka Server3。  
`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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
        <modelVersion>4.0.0</modelVersion>
    
        <groupId>com.kaven</groupId>
        <artifactId>eureka2</artifactId>
        <version>0.0.1-SNAPSHOT</version>
    
        <name>eureka2</name>
        <description>Demo project for Spring Boot</description>
    
        <parent>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-parent</artifactId>
            <version>2.0.6.RELEASE</version>
            <relativePath/> 
        </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.SR2</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>
    </project>

`application.yml`如下：

eureka:
      client:
        service-url:
          defaultZone: http://localhost:8761/eureka/,http://localhost:8762/eureka/
        register-with-eureka: true
      server:
        enable-self-preservation: true
    
    spring:
      application:
        name: eureka2
    
    server:
      port: 8763

启动类：

package com.kaven.eureka;
    
    import org.springframework.boot.SpringApplication;
    import org.springframework.boot.autoconfigure.SpringBootApplication;
    import org.springframework.cloud.netflix.eureka.server.EnableEurekaServer;
    
    @SpringBootApplication
    @EnableEurekaServer
    public class Eureka2Application { 
    
        public static void main(String[] args) { 
            SpringApplication.run(Eureka2Application.class, args);
        }
    }

创建第四个Spring Boot项目作为Eureka Client。  
`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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
        <modelVersion>4.0.0</modelVersion>
    
        <groupId>com.kaven</groupId>
        <artifactId>eureka-client</artifactId>
        <version>0.0.1-SNAPSHOT</version>
    
        <name>eureka-client</name>
        <description>Demo project for Spring Boot</description>
    
        <parent>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-parent</artifactId>
            <version>2.0.6.RELEASE</version>
            <relativePath/> 
        </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.SR2</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-web</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>

`application.yml`如下：

eureka:
      client:
        service-url:
          defaultZone: http://localhost:8761/eureka/,http://localhost:8762/eureka/,http://localhost:8763/eureka/
    
    spring:
      application:
        name: eureka-client
    
    server:
      port: 8080

启动类：

package com.kaven.eureka;
    
    import org.springframework.boot.SpringApplication;
    import org.springframework.boot.autoconfigure.SpringBootApplication;
    import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
    
    @SpringBootApplication
    @EnableDiscoveryClient
    public class EurekaClientApplication { 
    
        public static void main(String[] args) { 
            SpringApplication.run(EurekaClientApplication.class, args);
        }
    }

现在项目都创建好了，将四个项目都运行起来。

Eureka Server1的界面。  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM3OTYwNjAz_size_16_color_FFFFFF_t_70 1]  
Eureka Server2的界面。  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM3OTYwNjAz_size_16_color_FFFFFF_t_70 2]

Eureka Server3的界面。  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM3OTYwNjAz_size_16_color_FFFFFF_t_70 3]  
现在是不是每个服务都在所有的Eureka Server上了。

我们来停止运行Eureka Server1，来模拟分布式环境中某个注册中心宕机的情况。

停止运行Eureka Server1一会后，再来看一看Eureka Server2的界面。  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM3OTYwNjAz_size_16_color_FFFFFF_t_70 4]  
由于设置了开启自我保护机制，所以Eureka Server2界面会有警告，但是不会注销Eureka Server1，这是因为开启了自我保护机制。

当然服务本身也可以搞成分布式，即在多个区域部署一样的服务，这样不管是注册中心或者是服务挂掉后（只要没有全部挂掉），客户端就还可以获取服务注册表，以便请求服务。

写博客是博主记录自己的学习过程，如果有错误，请指正，谢谢！

扩展阅读:

*  [Eureka工作原理][Eureka]

[Link 1]: https://kaven.blog.csdn.net/article/details/109063924
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[Eureka]: https://blog.csdn.net/qq_37960603/article/details/109081684