SpringCloud——Eureka 服務註冊與發現

1. 單機 Eureka 構建

1.1 創建 EurekaServer 服務註冊中心

a. 建 moudle

b. 改 pom

<dependencies>
        <!--eureka server-->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
        </dependency>
        <!--自定義通用包-->
        <dependency>
            <groupId>com.zth.springcloud</groupId>
            <artifactId>cloud-api-commons</artifactId>
            <version>${project.version}</version>
        </dependency>
        <!--boot web actuator-->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-actuator</artifactId>
        </dependency>

        <!--一般通用配置-->
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

c. 寫 YML

server:
  port: 7001
eureka:
  instance:
    hostname: localhost   # eureka 服務端的示例名稱
  client:
    # false ：不向註冊中心註冊自己
    register-with-eureka: false
    # false：表示自己就是註冊中心，職責是維護服務實例，不需要去檢索服務
    fetch-registry: false
    # 設置 eureka 服務地址
    service-url:
      defaultZoon: http://${eureka.instance.hostname}:${server.port}/eureka/

d. 主啓動

@SpringBootApplication
@EnableEurekaServer
public class EurekaMain7001 {
    public static void main(String[] args){
        SpringApplication.run(EurekaMain7001.class,args);
    }
}

e. 測試

1.2 Eureka 註冊服務提供者

a. 改 pom

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

b. 寫 YML

eureka:
  client:
    register-with-eureka: true
    fetchRegistry: true
    service-url:
      defaultZone: http://localhost:7001/eureka

c. 主啓動

添加 @EnableEurekaClient

@EnableEurekaClient
@SpringBootApplication
public class PaymentMain8001 {
    public static void main(String[] args){
        SpringApplication.run(PaymentMain8001.class,args);
    }
}

d. 測試

先啓動 EurekaServer

【注】服務提供者和服務消費者入駐 Eureka 一致。

2. Eureka 集羣

2.1 創建兩個 EurekaServer

cloud-eureka-server7001

cloud-eureka-server7002

2.2 修改映射文件

127.0.0.1  eureka7001.com
127.0.0.1  eureka7002.com

2.3 寫 YML

cloud-eureka-server7001:

server:
  port: 7001

eureka:
  instance:
    hostname:  eureka7001.com   # eureka 服務端的示例名稱
  client:
    # false ：不向註冊中心註冊自己
    register-with-eureka: false
    # false：表示自己就是註冊中心，職責是維護服務實例，不需要去檢索服務
    fetch-registry: false
    # 設置 eureka 服務地址
    service-url:
      defaultZone: http://eureka7002.com:7002/eureka/

cloud-eureka-server7002:

server:
  port: 7002

eureka:
  instance:
    hostname:  eureka7002.com   # eureka 服務端的示例名稱
  client:
    # false ：不向註冊中心註冊自己
    register-with-eureka: false
    # false：表示自己就是註冊中心，職責是維護服務實例，不需要去檢索服務
    fetch-registry: false
    # 設置 eureka 服務地址
    service-url:
      defaultZone: http://eureka7001.com:7001/eureka/

2.4 服務提供者發佈到集羣

服務提供者 cloud-payment-server8001 YML:

eureka:
  client:
    register-with-eureka: true
    fetchRegistry: true
    service-url:
      defaultZone: http://eureka7001.com:7001/eureka,http://eureka7002.com:7002/eureka

2.5 測試

3. 服務提供者集羣

兩個服務提供者：

cloud-provider-payment8001

cloud-provider-payment8002

YML 配置：

spring:
  application:
    name: cloud-payment-service
  datasource:
    type: com.alibaba.druid.pool.DruidDataSource    # 當前數據源操作類型
    driver-class-name: org.gjt.mm.mysql.Driver    # mysql 驅動包
    url: jdbc:mysql://localhost:3306/mycloud?useUnicode=true&characterEncoding=utf-8&useSSL=false
    username: root
    password: mysql

eureka:
  client:
    register-with-eureka: true
    fetchRegistry: true
    service-url:
      defaultZone: http://eureka7001.com:7001/eureka,http://eureka7002.com:7002/eureka

兩個服務提供者的 application.name 一致，則認爲是同一個服務提供者。

即：將提供相同服務的不同的服務提供者 application.name 保持一致，並註冊到 Erueka，就完成了服務提供者集羣。

4. 服務消費者獲取提供者服務

4.1 修改服務地址

@RestController
@Slf4j
public class OrderController {
    /**
     * public static final String PAYMENT_URL = "http://localhost:8001";
     */
    
    public static final String PAYMENT_URL = "http://CLOUD-PAYMENT-SERVICE";
    @Autowired
    private RestTemplate restTemplate;

    @GetMapping("/consumer/payment/create")
    public CommonResult<Payment> create(Payment payment){
        return restTemplate.postForObject(PAYMENT_URL+"/payment/create",payment,CommonResult.class);
    }

    @GetMapping("/consumer/payment/get/{id}")
    public CommonResult<Payment> getPayment(@PathVariable("id") long id){
        return restTemplate.getForObject(PAYMENT_URL+"/payment/get/"+id,CommonResult.class);
    }

}

4.2 RestTemplate 添加負載均衡

@Configuration
public class ApplicationContextConfig {
    @Bean
    @LoadBalanced
    public RestTemplate getRestTemplate(){
        return new RestTemplate();
    }
}

5. 完善 actuator 微服務信息

5.1 修改服務名稱

eureka:
  client:
    register-with-eureka: true
    fetchRegistry: true
    service-url:
      defaultZone: http://eureka7001.com:7001/eureka,http://eureka7002.com:7002/eureka
  instance:
    instance-id: payment8001
    prefer-ip-address: true

instance-id: payment8001：修改服務名稱
prefer-ip-address: true：訪問信息是否提示 ip

5.2 添加微服務 info

a. 添加 pom

<build>
    <resources>
        <resource>
            <directory>src/main/resources</directory>
            <filtering>true</filtering>
        </resource>
    </resources>
</build>

b. 配置 YML

info:
  groupId: "@groupId@"
  artifactId: "@artifactId@"
  version: "@version@"
  principal: 張三
  phone: 110

c. 查看 info

6. 服務發現 Discovery

可以通過服務發現獲得註冊進 eureka 裏面微服務的信息。

6.1 修改 controller

@Autowired
    private DiscoveryClient discoveryClient;

    @GetMapping(value = "/payment/discovery")
    public Object discovery(){
        List<String> services = discoveryClient.getServices();
        for (String element : services) {
            log.info("element:"+element);
        }

        List<ServiceInstance> instances = discoveryClient.getInstances("CLOUD-PAYMENT-SERVICE");
        for (ServiceInstance instance : instances) {
            log.info(instance.getServiceId()+"\t"+instance.getHost()+"\t"+instance.getPort()+"\t"+instance.getUri());
        }
        return this.discoveryClient;
    }

【注】import org.springframework.cloud.client.discovery.DiscoveryClient;

6.2 修改啓動類

啓動類添加 @EnableDiscoveryClient

6.3 測試結果

7. Erueka 自我保護

7.1 自我保護機制

爲了防止 EurekaClient 可以正常運行但與 EurekaServer 網絡不通情況下，EurekaServer 立刻剔除 EurekaClient。

默認情況下，如果 EurekaServer 在一定時間內沒有接收到某個微服務實例的心跳，EurekaServer 將會註銷該實例 (默認90秒)

7.2 禁止自我保護

EurekaServer 端 YML:

eureka.server.enable-self-preservation=false 關閉自我保護

eureka:
  instance:
    hostname:  eureka7001.com   # eureka 服務端的示例名稱
  client:
    # false ：不向註冊中心註冊自己
    register-with-eureka: false
    # false：表示自己就是註冊中心，職責是維護服務實例，不需要去檢索服務
    fetch-registry: false
    # 設置 eureka 服務地址
    service-url:
      defaultZone: http://eureka7002.com:7002/eureka/
  server:
    enable-self-preservation: false

EurekaClient 端：

eureka:
  client:
    register-with-eureka: true
    fetchRegistry: true
    service-url:
      defaultZone: http://eureka7001.com:7001/eureka,http://eureka7002.com:7002/eureka
  instance:
    instance-id: payment8001
    prefer-ip-address: true
    # Eureka 客戶端向服務端發送心跳的時間間隔，單位爲秒(默認是30秒)
    lease-expiration-duration-in-seconds: 1
    # Eureka 服務端在收到最後一次心跳後等待時間上限， 單位爲秒(默認是90秒)，超時將剔除服務
    lease-renewal-interval-in-seconds: 3