Eureka是SpringCloud中的一个负责服务注册与发现的组件。Eureka中分为Server和Client：

    • Server是服务的注册与发现中心，Server端无需向注册中心注册，因为Server本身就是注册中心
    • Client既可以作为服务的生产者，又可以作为服务的消费者。生产者Client和消费者Client都必须向注册中心注册

    Eureka结构如下图：
    1635423824790-21b04da1-8f98-4a34-954c-a3a11eb472bb2.jpg :::info 服务中心Server:8761 ::: 添加spring-cloud-starter-netflix-eureka-server依赖

    1. <parent>
    2.   <groupId>org.springframework.boot</groupId>
    3.   <artifactId>spring-boot-starter-parent</artifactId>
    4.   <version>2.0.6.RELEASE</version>
    5.   <relativePath/> <!-- lookup parent from repository -->
    6. </parent>
    7. <properties>
    8.   <java.version>1.8</java.version>
    9.   <spring-cloud.version>Finchley.SR2</spring-cloud.version>
    10. </properties>
    12. <dependencies>
    13.   <dependency>
    14.     <groupId>org.springframework.cloud</groupId>
    15.     <artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
    16.   </dependency>
    17.   <dependency>
    18.     <groupId>org.springframework.boot</groupId>
    19.     <artifactId>spring-boot-starter-security</artifactId>
    20.   </dependency>
    21.   <dependency>
    22.     <groupId>org.projectlombok</groupId>
    23.     <artifactId>lombok</artifactId>
    24.     <optional>true</optional>
    25.   </dependency>
    26.   <dependency>
    27.     <groupId>org.springframework.boot</groupId>
    28.     <artifactId>spring-boot-starter-test</artifactId>
    29.     <scope>test</scope>
    30.     <exclusions>
    31.       <exclusion>
    32.         <groupId>org.junit.vintage</groupId>
    33.         <artifactId>junit-vintage-engine</artifactId>
    34.       </exclusion>
    35.     </exclusions>
    36.   </dependency>
    37. </dependencies>
    39. <dependencyManagement>
    40.   <dependencies>
    41.     <dependency>
    42.       <groupId>org.springframework.cloud</groupId>
    43.       <artifactId>spring-cloud-dependencies</artifactId>
    44.       <version>${spring-cloud.version}</version>
    45.       <type>pom</type>
    46.       <scope>import</scope>
    47.     </dependency>
    48.   </dependencies>
    49. </dependencyManagement>

    在SpringBoot启动类上添加注解@EnableEurekaServer

    1. @SpringBootApplication
    2. //开启服务治理功能
    3. @EnableEurekaServer
    4. public class EurekaServerApplication {
    5.     public static void main(String[] args) {
    6.         SpringApplication.run(EurekaServerApplication.class, args);
    7.     }
    8. }

    集成Security框架，实现Eureka密码登录

    1. @EnableWebSecurity
    2. @Configuration
    3. public class WebSecurityConfig extends WebSecurityConfigurerAdapter {
    4.     @Override
    5.     protected void configure(HttpSecurity http) throws Exception {
    6.         http.csrf().disable();
    7.         http.authorizeRequests()
    8.                 .anyRequest()
    9.                 .authenticated()
    10.                 .and()
    11.                 .httpBasic();
    12.     }
    13. }

    配置文件：

    1. spring:
    2.   application:
    3. # 服务名
    4.     name: eureka-server
    5. # security安全认证配置
    6.   security:
    7.     user:
    8.       name: yangle
    9.       password: 123
    10. server:
    11.   port: 8761
    12. eureka:
    13.   client:
    14. #  该应用为注册中心，不需要向注册中心注册自己
    15.     register-with-eureka: false
    16. #    关闭检索服务的功能，只需要维护服务
    17.     fetch-registry: false

    项目启动后，访问http://localhost:8761/，输入用户名和密码 yangle 123
    目前我们还没有创建服务，因此下图Application栏目没有服务实例
    7870e944-49e0-4e78-a831-ba38271cfefe.jpg :::info 生产者客户端:8081 ::: 生产者会向服务中心注册自己的服务并周期性的发送心跳

    • 心跳间隔默认30s：eureka.instance.lease-renewal-interval-in-seconds=5
    • 心跳超时时间默认90s：eureka.instance.lease-expiration-duration-in-seconds=10

    同时生产者也会周期性的从服务中心获取服务清单信息缓存到本地

    • 是否从eureka获取服务清单：fetch-registry: true
    • 向eureka服务端更新自己实例信息的间隔时间s：instance-info-replication-interval-seconds: 15
    • 从eureka客户端获得服务清单的间隔时间s：registry-fetch-interval-seconds: 15

    添加spring-cloud-starter-netflix-eureka-client依赖：

    1.     <parent>
    2.         <groupId>org.springframework.boot</groupId>
    3.         <artifactId>spring-boot-starter-parent</artifactId>
    4.         <version>2.0.6.RELEASE</version>
    5.         <relativePath/> <!-- lookup parent from repository -->
    6.     </parent>
    7.     <properties>
    8.         <java.version>1.8</java.version>
    9.         <spring-cloud.version>Finchley.SR2</spring-cloud.version>
    10.     </properties>
    12.     <dependencies>
    13.         <dependency>
    14.             <groupId>org.springframework.cloud</groupId>
    15.             <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
    16.         </dependency>
    17.         <dependency>
    18.             <groupId>org.springframework.boot</groupId>
    19.             <artifactId>spring-boot-starter-web</artifactId>
    20.         </dependency>
    21.         <dependency>
    22.             <groupId>org.springframework.boot</groupId>
    23.             <artifactId>spring-boot-starter-test</artifactId>
    24.             <scope>test</scope>
    25.             <exclusions>
    26.                 <exclusion>
    27.                     <groupId>org.junit.vintage</groupId>
    28.                     <artifactId>junit-vintage-engine</artifactId>
    29.                 </exclusion>
    30.             </exclusions>
    31.         </dependency>
    32.     </dependencies>
    34.     <dependencyManagement>
    35.         <dependencies>
    36.             <dependency>
    37.                 <groupId>org.springframework.cloud</groupId>
    38.                 <artifactId>spring-cloud-dependencies</artifactId>
    39.                 <version>${spring-cloud.version}</version>
    40.                 <type>pom</type>
    41.                 <scope>import</scope>
    42.             </dependency>
    43.         </dependencies>
    44.     </dependencyManagement>

    然后在启动类中添加注解@EnableEurekaClient

    1. @SpringBootApplication
    2. //开启服务发现功能
    3. @EnableDiscoveryClient
    4. public class EurekaClientProducterApplication {
    6.     public static void main(String[] args) {
    7.         SpringApplication.run(EurekaClientProducterApplication.class, args);
    8.     }
    10. }

    添加一个订单服务

    2. @RestController
    3. public class OrderService {
    4.     @RequestMapping("getOrder")
    5.     public String getOrder(){
    6.         return "{code:0,data:{}}";
    7.     }
    8. }

    在配置文件中添加配置信息：

    1. spring:
    2.   application:
    3.     name: eureka-client-order-service
    4. server:
    5.   port: 8081
    6. eureka:
    7.   client:
    8.     serviceUrl:
    9. #    指定注册中心
    10.       defaultZone: http://yangle:123@localhost:8761/eureka
    11.   instance:
    12. #可选
    13.     preferIpAddress: true
    14. #实例ID支持自定义，可选
    15.     instance-id: ${spring.application.name}:${spring.cloud.client.ip-address}:${server.port}

    我们重新打开http://localhost:8761/,会看到生产者已经注册到注册中心里面了
    daf75b64-be52-433c-9726-f97f461bac59.jpg :::info 消费者客户端:8082 ::: 将restTemplate注入到容器中，SpringRestTemplate是Spring提供的用于访问Rest服务的客端，RestTemplate提供了多种便捷访问远程Http服务的方法，能够大大提高客户端的编写效率，所以很多客户端比如Android或者第三方服务商都是使用RestTemplate请求restful服务

    1. @SpringBootApplication
    2. public class EurekaClientConsumerApplication {
    4.     public static void main(String[] args) {
    5.         SpringApplication.run(EurekaClientConsumerApplication.class, args);
    6.     }
    8.     @Bean(name = "restTemplate")
    9.     public RestTemplate getRestTemplate() {
    10.         return new RestTemplate();
    11.     }
    13.     @Bean(name = "restTemplate2")
    14.     @LoadBalanced//开启负载均衡，需要使用IDEA复制多份消费者
    15.     public RestTemplate getRestTemplate2() {
    16.         return new RestTemplate();
    17.     }
    18. }

    添加一个接口去调用生产者提供的服务

    1. @RestController
    2. public class OrderConsumerService {
    3.     @Autowired
    4.     @Qualifier("restTemplate")
    5.     private RestTemplate restTemplate;
    6.     @Autowired
    7.     @Qualifier("restTemplate2")
    8.     private RestTemplate restTemplate2;
    9.     @RequestMapping("getOrder")
    10.     public String getOrder(){
    11.         return restTemplate.getForObject("http://localhost:8081/getOrder",String.class);
    12.     }
    13.     //实现负载均衡的服务，不需要指定服务端口，只需要指定使用的服务名称
    14.     @RequestMapping("getOrderForLoadBalence")
    15.     public String getOrderForLoadBalence(){
    16.         return restTemplate2.getForObject("http://eureka-client-order-service/getOrder",String.class);
    17.     }
    18. }

    配置文件中添加配置信息：

    1. spring:
    2.   application:
    3.     name: eureka-client-order-consumer-service
    4. server:
    5.   port: 8082
    6. eureka:
    7.   client:
    8.     serviceUrl:
    9.       defaultZone: http://yangle:123@localhost:8761/eureka
    10.   instance:
    11.     preferIpAddress: true
    12.     instance-id: ${spring.application.name}:${spring.cloud.client.ip-address}:${server.port}

    查看eureka界面http://localhost:8761/，看到消费者也注册进来了
    53a055ff-5079-4802-bc20-915d6e0d5dfb.jpg :::info 高可用注册中心 ::: 服务注册中心集群方式部署，当其中某个注册中心分片故障后，Eureka就会转入自我保护模式，允许在故障期间继续进行服务注册与发现；
    等到故障分片恢复时，集群其他分片会把它们的状态同步给故障分片；
    集群中的分片会以异步的方式互相复制各自的状态；
    复制eureka-server项目，更名为eureka-server-slave，eureka-server-slave的配置文件如下：

    1. spring:
    2.   application:
    3.     name: eureka-server
    4.   security:
    5.     user:
    6.       name: yangle
    7.       password: 123
    8. server:
    9.   port: 8762
    10. eureka:
    11.   client:
    12.     serviceUrl:
    13.       defaultZone: http://yangle:123@localhost:8761/eureka

    修改eureka-server的配置文件

    1. spring:
    2.   application:
    3.     name: eureka-server
    4.   security:
    5.     user:
    6.       name: yangle
    7.       password: 123
    8. server:
    9.   port: 8761
    10. eureka:
    11.   client:
    12.     serviceUrl:
    13.       defaultZone: http://yangle:123@localhost:8762/eureka

    修改producter的配置文件

    1. spring:
    2.   application:
    3.     name: eureka-client-order-service
    4. server:
    5.   port: 8081
    6. eureka:
    7.   client:
    8.     serviceUrl:
    9.       defaultZone: http://yangle:123@localhost:8761/eureka,http://yangle:123@localhost:8762/eureka
    10.   instance:
    11.     preferIpAddress: true
    12.     instance-id: ${spring.application.name}:${spring.cloud.client.ip-address}:${server.port}

    修改consumer的配置文件

    1. spring:
    2.   application:
    3.     name: eureka-client-order-consumer-service
    4. server:
    5.   port: 8082
    6. eureka:
    7.   client:
    8.     serviceUrl:
    9.       defaultZone: http://yangle:123@localhost:8761/eureka,http://yangle:123@localhost:8762/eureka
    10.   instance:
    11.     preferIpAddress: true
    12.     instance-id: ${spring.application.name}:${spring.cloud.client.ip-address}:${server.port}