[Java知识库]Eureka

一、Eureka的Server端
1.创建Eureka的maven项目

2.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">
    <parent>
        <artifactId>SpringCloud2021</artifactId>
        <groupId>com.atguigu.springcloud</groupId>
        <version>1.0-SNAPSHOT</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>

    <artifactId>03-cloud-eureka-server7001</artifactId>

    <dependencies>
        <!-- https://mvnrepository.com/artifact/org.springframework.cloud/spring-cloud-starter-eureka-server -->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
        </dependency>

        <dependency>
            <groupId>com.atguigu.springcloud</groupId>
            <artifactId>cloud-api-commons</artifactId>
            <version>${project.version}</version>
        </dependency>

        <!-- https://mvnrepository.com/artifact/org.springframework.boot/spring-boot-starter-web -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <!-- https://mvnrepository.com/artifact/org.springframework.boot/spring-boot-starter-web  -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-actuator</artifactId>
        </dependency>

        <!-- https://mvnrepository.com/artifact/org.springframework.boot/spring-boot-devtools -->
        <!--<dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <scope>runtime</scope>
            <optional>true</optional>
        </dependency>-->

        <!-- https://mvnrepository.com/artifact/org.projectlombok/lombok -->
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
        </dependency>

        <!-- https://mvnrepository.com/artifact/org.springframework.boot/spring-boot-starter-test -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
        </dependency>
    </dependencies>
</project>

3.配置application.yml

server:
  port: 7001

eureka:
  instance:
    hostname: localhost  #eureka服务端的实例名字
  client:
    register-with-eureka: false    #表识不向注册中心注册自己
    fetch-registry: false   #表示自己就是注册中心，职责是维护服务实例，并不需要去检索服务
    service-url:
      defaultZone: http://${eureka.instance.hostname}:${server.port}/eureka/    #设置与eureka server交互的地址查询服务和注册服务都需要依赖这个地址

4.启动服务后访问http://localhost:7001

二、Eureka的Client端
1.pom.xml

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

2.application.yml

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

3.主启动类

4.访问http://localhost:7001

三、Eureka集群

1、创建04-cloud-eureka-server7002项目
2、配置本地映射文件

3、更改7001和7002的application.yml文
7001

server:
  port: 7001

eureka:
  instance:
    hostname: eureka7001.com  #eureka服务端的实例名字
  client:
    register-with-eureka: false    #表识不向注册中心注册自己
    fetch-registry: false   #表示自己就是注册中心，职责是维护服务实例，并不需要去检索服务
    service-url:
      defaultZone: http://eureka7002.com:7002/eureka/    #设置与eureka server交互的地址查询服务和注册服务都需要依赖这个地址

7002

server:
  port: 7002

eureka:
  instance:
    hostname: eureka7002.com  #eureka服务端的实例名字
  client:
    register-with-eureka: false    #表识不向注册中心注册自己
    fetch-registry: false   #表示自己就是注册中心，职责是维护服务实例，并不需要去检索服务
    service-url:
      defaultZone: http://eureka7001.com:7001/eureka/    #设置与eureka server交互的地址查询服务和注册服务都需要依赖这个地址

4.访问


四、项目注册到两个Eureka
1、更改配置文件

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

2、访问


五、微服务提供端配置集群
1、创建05-cloud-provider-payment8002
2、配置application.yml

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

3、配置调用显示端口

4、修改调用微服务的项目RestTemplate的请求url为服务名

6、开启RestTemplate的负载均衡

package com.atguigu.springcloud.config;

import org.springframework.cloud.client.loadbalancer.LoadBalanced;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.client.RestTemplate;

@Configuration
public class ApplicationContextConfig
{
    @Bean
    @LoadBalanced//开启负载均衡！！！
    public RestTemplate getRestTemplate(){
        return new RestTemplate();
    }
}

7、访问


*注意事项

1、显示主机名，解决办法
配置8001 8002微服务提供者的application.yml文件

eureka:
  client:
    fetch-registry: true
    register-with-eureka: true
    service-url:
      defaultZone: http://eureka7001.com:7001/eureka,http://eureka7002.com:7002/eureka
  instance:
    instance-id: payment8002

最后两行
2、健康检查 http://localhost:8001/actuator/health
加上/actuator/health访问

3、获取焦点显示ip

图片左下角192.168.56.1
配置8001、8002的application.yml

eureka:
  client:
    fetch-registry: true
    register-with-eureka: true
    service-url:
      defaultZone: http://eureka7001.com:7001/eureka,http://eureka7002.com:7002/eureka
  instance:
    instance-id: payment8002
    prefer-ip-address: true

最后一行：prefer-ip-address: true

六、服务发现Discovery
对于注册进eureka里面的微服务，可以通过服务发现来获得该服务的信息
1、编辑controller

package com.atguigu.springcloud.controller;


import com.atguigu.springcloud.entities.CommonResult;
import com.atguigu.springcloud.entities.Payment;
import com.atguigu.springcloud.service.PaymentService;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.cloud.client.ServiceInstance;
import org.springframework.cloud.client.discovery.DiscoveryClient;
import org.springframework.web.bind.annotation.*;

import javax.annotation.Resource;
import java.util.List;

@RestController
@Slf4j
public class PaymentController {
    @Resource
    private PaymentService paymentService;

    @Resource
    private DiscoveryClient discoveryClient;

    @Value("${server.port}")
    private String serverPort;

    @PostMapping(value = "/payment/create")
    public CommonResult create(@RequestBody Payment payment){
        int result = paymentService.create(payment);
        log.info("*****插入结果："+result);
        if (result>0){  //成功
            return new CommonResult(200,"插入数据库成功,serverPort:"+serverPort,result);
        }else {
            return new CommonResult(444,"插入数据库失败",null);
        }
    }

    @GetMapping(value = "/payment/get/{id}")
    public CommonResult getPaymentById(@PathVariable("id") Long id){
        Payment payment = paymentService.getPaymentById(id);
        log.info("*****查询结果："+payment);
        if (payment!=null){  //说明有数据，能查询成功
            return new CommonResult(200,"查询成功,serverPort:"+serverPort,payment);
        }else {
            return new CommonResult(444,"没有对应记录，查询ID："+id,null);
        }
    }

    @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()+instance.getPort()+"\t"+instance.getUri());
        }
        return this.discoveryClient;
    }

}

2、8001主启动类加@EnableDiscoveryClient
3、访问


七、Eureka自我保护

一句话：某时刻某一个微服务不可用了，Eureka不会立刻清理，依旧会对该微服务的信息进行保存
属于CAP里面的AP分支




禁止自我保护
出厂默认，自我保护机制是开启的：eureka.server.enable-self-preservation = true
使用eureka.server.enable-self-preservation = false可以禁用自我保护模式
7001配置文件

server:
  enable-self-preservation: false  #关闭自我保护机制
  eviction-interval-timer-in-ms: 2000

8001配置文件

eureka:
  client:
    fetch-registry: true
    register-with-eureka: true
    service-url:
      defaultZone: http://eureka7001.com:7001/eureka,http://eureka7002.com:7002/eureka
  instance:
      instance-id: payment8001
      prefer-ip-address: true
      lease-renewal-interval-in-seconds:  1   #Eureka客户端向服务端发送心跳的时间间隔，单位为秒（默认是30秒）
      lease-expiration-duration-in-seconds:  2    #Eureka服务端在收到最后一次心跳后等待时间上限，单位为秒（默认是90秒），超时将剔除服务