SpringCloud-Hystrix

一、介绍

（1）避免单个服务出现故障导致整个应用崩溃。
（2）服务降级：服务超时、服务异常、服务宕机时，执行定义好的方法。（做别的）
（3）服务熔断：达到熔断条件时，服务禁止被访问，执行定义好的方法。（不做了）
（4）服务限流：高并发场景下的一大波流量过来时，让其排队访问。（排队做）

二、构建项目

（1）pom.xml

<dependencies><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-netflix-hystrix</artifactId></dependency><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-netflix-eureka-client</artifactId></dependency><dependency><groupId>com.wsh.springcloud</groupId><artifactId>cloud-api-common</artifactId><version>1.0-SNAPSHOT</version></dependency><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><dependency><groupId>org.mybatis.spring.boot</groupId><artifactId>mybatis-spring-boot-starter</artifactId></dependency><dependency><groupId>com.alibaba</groupId><artifactId>druid-spring-boot-starter</artifactId></dependency><dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-jdbc</artifactId></dependency><dependency><groupId>org.projectlombok</groupId><artifactId>lombok</artifactId></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-test</artifactId><scope>test</scope></dependency></dependencies>

（2）编写application.yml文件

server:port: 8001spring:application:name: cloud-provider-hystrix-paymentdatasource:type: com.alibaba.druid.pool.DruidDataSourcedriver-class-name: org.gjt.mm.mysql.Driverurl: jdbc:mysql://localhost:3306/springcloud?useUnicode=true&characterEncoding=utf-8&useSSL=falseusername: rootpassword: wsh666eureka:client:register-with-eureka: truefetch-registry: trueservice-url:defaultZone: http://eureka1.com:7001/eurekainstance:instance-id: hystrixPayment8001prefer-ip-address: true

（3）启动类PaymentHystrixMain8001

package com.wsh.springcloud;import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;/*** @ClassName PaymentHystrixMain8001* @Description: TODO* @Author wshaha* @Date 2023/10/14* @Version V1.0**/
@SpringBootApplication
@EnableEurekaClient
public class PaymentHystrixMain8001 {public static void main(String[] args) {SpringApplication.run(PaymentHystrixMain8001.class, args);}
}

（4）编写PaymentService

package com.wsh.springcloud.service;import lombok.extern.slf4j.Slf4j;
import org.springframework.stereotype.Service;/*** @ClassName PaymentService* @Description: TODO* @Author wshaha* @Date 2023/10/14* @Version V1.0**/
@Service
@Slf4j
public class PaymentService {public String test1(Integer id){return "test1: " + Thread.currentThread().getName() + " " + id;}public String test2(Integer id){try {Thread.sleep(3000);} catch (Exception e){}return "test2: " + Thread.currentThread().getName() + " " + id;}
}

（5）编写PaymentController

package com.wsh.springcloud.controller;import com.wsh.springcloud.service.PaymentService;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;/*** @ClassName PaymentController* @Description: TODO* @Author wshaha* @Date 2023/10/14* @Version V1.0**/
@Slf4j
@RequestMapping("/payment")
@RestController
public class PaymentController {@Autowiredprivate PaymentService paymentService;@GetMapping("/test1/{id}")public String test1(@PathVariable("id") Integer id){return paymentService.test1(id);}@GetMapping("/test2/{id}")public String test2(@PathVariable("id") Integer id){return paymentService.test2(id);}
}

（6）运行

三、 服务降级配置

（1）方式一（一旦方法出现异常或超时了，会调用@HystrixCommand的降级方法）

注：@EnableCircuitBreaker用于启动断路器，支持多种断路器，@EnableHystrix用于启动断路器，只支持Hystrix断路器

a、PaymentService编写降级方法，配置注解@HystrixCommand

@Service
@Slf4j
public class PaymentService {public String test1(Integer id){return "test1: " + Thread.currentThread().getName() + " " + id;}@HystrixCommand(fallbackMethod = "test2fallback", commandProperties = {@HystrixProperty(name = "execution.isolation.thread.timeoutInMilliseconds", value = "2000")})public String test2(Integer id){try {Thread.sleep(3000);} catch (Exception e){}return "test2: " + Thread.currentThread().getName() + " " + id;}public String test2fallback(Integer id){return "test2fallback: " + id;}
}

b、启动类开启断路器

@SpringBootApplication
@EnableEurekaClient
@EnableCircuitBreaker
public class PaymentHystrixMain8001 {public static void main(String[] args) {SpringApplication.run(PaymentHystrixMain8001.class, args);}
}

c、运行

（2）方式二（配置全局使用的降级方法）
a、使用@DefaultProperties，注意全局降级方法的参数列表为空

@Slf4j
@RequestMapping("/payment")
@RestController
@DefaultProperties(defaultFallback = "defaultFallbacktest")
public class PaymentController {@Autowiredprivate PaymentService paymentService;@GetMapping("/test1/{id}")public String test1(@PathVariable("id") Integer id){return paymentService.test1(id);}@GetMapping("/test2/{id}")@HystrixCommandpublic String test2(@PathVariable("id") Integer id){return paymentService.test2(id);}public String defaultFallbacktest(){return "defaultFallbacktest";}
}

b、编写PaymentService

@Service
@Slf4j
public class PaymentService {public String test1(Integer id){return "test1: " + Thread.currentThread().getName() + " " + id;}//    @HystrixCommand(fallbackMethod = "test2fallback", commandProperties = {
//            @HystrixProperty(name = "execution.isolation.thread.timeoutInMilliseconds", value = "2000")
//    })public String test2(Integer id){
//        try {
//            Thread.sleep(3000);
//        } catch (Exception e){
//
//        }int i = 1 / 0;return "test2: " + Thread.currentThread().getName() + " " + id;}
//    public String test2fallback(Integer id){
//        return "test2fallback: " + id;
//    }
}

c、运行

（3）方式三，feign调用其他服务时，可以利用实现类对应降级方法
a、pom.xml增加依赖

<dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-openfeign</artifactId></dependency>

b、application.yml增加

feign:hystrix:enabled: true

c、编写远程调用接口FeignTestService

@Component
@FeignClient(value = "CLOUD-PAYMENT-SERVICE", fallback = FeignTestServiceImpl.class)
public interface FeignTestService {@GetMapping("/payment/test")public CommonResult<String> test();
}

d、编写降级方法类FeignTestServiceImpl

@Component
public class FeignTestServiceImpl implements FeignTestService{@Overridepublic CommonResult<String> test() {return new CommonResult(444, "", "error");}
}

e、编写Controller

@Slf4j
@RequestMapping("/payment")
@RestController
//@DefaultProperties(defaultFallback = "defaultFallbacktest")
public class PaymentController {@Autowiredprivate PaymentService paymentService;@Autowiredprivate FeignTestService feignTestService;@GetMapping("/test1/{id}")public String test1(@PathVariable("id") Integer id){return paymentService.test1(id);}@GetMapping("/test2/{id}")
//    @HystrixCommandpublic String test2(@PathVariable("id") Integer id){return paymentService.test2(id);}
//    public String defaultFallbacktest(){
//        return "defaultFallbacktest";
//    }@GetMapping("/test")public CommonResult<String> test(){return feignTestService.test();}
}

f、运行

四、服务熔断配置

（1）服务先降级，然后熔断，后面尝试恢复
（2）在规定时间内，接口访问量超过设置阈值，并且失败率大于等于设置阈值
（3）例子

@Service
@Slf4j
public class PaymentService {@HystrixCommand(fallbackMethod = "test1fallback", commandProperties = {@HystrixProperty(name = "circuitBreaker.enabled", value = "true"),//开启断路器@HystrixProperty(name = "circuitBreaker.requestVolumeThreshold", value = "10"),//请求次数阈值@HystrixProperty(name = "circuitBreaker.sleepWindowInMilliseconds", value = "10000"),//规定时间内@HystrixProperty(name = "circuitBreaker.errorThresholdPercentage", value = "60")//失败率阈值})public String test1(Integer id){int i = 1 / id;return "test1: " + Thread.currentThread().getName() + " " + id;}public String test1fallback(Integer id){return "test1fallback: " + id;}//    @HystrixCommand(fallbackMethod = "test2fallback", commandProperties = {
//            @HystrixProperty(name = "execution.isolation.thread.timeoutInMilliseconds", value = "2000")
//    })public String test2(Integer id){
//        try {
//            Thread.sleep(3000);
//        } catch (Exception e){
//
//        }int i = 1 / 0;return "test2: " + Thread.currentThread().getName() + " " + id;}
//    public String test2fallback(Integer id){
//        return "test2fallback: " + id;
//    }
}

五、监控界面搭建（只能监控hystrix接管的方法）

（1）编写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>demo20220821</artifactId><groupId>com.wsh.springcloud</groupId><version>1.0-SNAPSHOT</version></parent><modelVersion>4.0.0</modelVersion><artifactId>cloud-consumer-hystrix-dashboard9001</artifactId><dependencies><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-netflix-hystrix-dashboard</artifactId></dependency><dependency><groupId>com.wsh.springcloud</groupId><artifactId>cloud-api-common</artifactId><version>1.0-SNAPSHOT</version></dependency><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>--><dependency><groupId>org.projectlombok</groupId><artifactId>lombok</artifactId></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-test</artifactId><scope>test</scope></dependency></dependencies>
</project>

（2）编写application.yml

server:port: 9001spring:application:name: cloud-hystrix-dashboard

（3）编写启动类

package com.wsh.springcloud;import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.hystrix.dashboard.EnableHystrixDashboard;/*** @ClassName HystrixDashboardMain9001* @Description: TODO* @Author wshaha* @Date 2023/10/14* @Version V1.0**/
@SpringBootApplication
@EnableHystrixDashboard
public class HystrixDashboardMain9001 {public static void main(String[] args) {SpringApplication.run(HystrixDashboardMain9001.class, args);}
}

（4）运行

（5）配置被监控的项目
a、pom.xml

加上探针spring-boot-starter-actuator

b、启动类加上

package com.wsh.springcloud;import com.netflix.hystrix.contrib.metrics.eventstream.HystrixMetricsStreamServlet;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.web.servlet.ServletRegistrationBean;
import org.springframework.cloud.client.circuitbreaker.EnableCircuitBreaker;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
import org.springframework.cloud.openfeign.EnableFeignClients;
import org.springframework.context.annotation.Bean;/*** @ClassName PaymentHystrixMain8001* @Description: TODO* @Author wshaha* @Date 2023/10/14* @Version V1.0**/
@SpringBootApplication
@EnableEurekaClient
@EnableCircuitBreaker
@EnableFeignClients
public class PaymentHystrixMain8001 {public static void main(String[] args) {SpringApplication.run(PaymentHystrixMain8001.class, args);}@Beanpublic ServletRegistrationBean getServlet(){HystrixMetricsStreamServlet hystrixMetricsStreamServlet = new HystrixMetricsStreamServlet();ServletRegistrationBean servletRegistrationBean = new ServletRegistrationBean(hystrixMetricsStreamServlet);servletRegistrationBean.setLoadOnStartup(1);servletRegistrationBean.addUrlMappings("/hystrix.stream");servletRegistrationBean.setName("HystrixMetricsStreamServlet");return servletRegistrationBean;}
}

（6）监控界面