Hystrix 豪猪哥

服务雪崩

多个微服务之间调用的时候，假设微服务A调用微服务B和微服务C，微服务B和C又调用其它微服务，这就是“扇出”。如果扇出的链路上某个微服务的调用响应时间过长或者不可用，对微服务A的调用就会占用越来越多的系统资源，进而引起系统崩溃，即为雪崩效应。

Hystrix

Hystrix是一个用于处理分布式系统的延迟和容错的开源库，在分布式系统里面，许多依赖不可避免的会调用失败，比如超时，异常等，Hystrix能够保证在一个依赖出问题的情况下，不会导致整体服务失败，避免级联故障，以提高分布式的弹性。

断路器，本身是一个开关装置，当某个服务单元发生故障后，通过断路器的故障监控（类似熔断保险丝），向调用方返回一个符合预期的，可处理的备选响应（FallBack），而不是长时间等待或者抛出异常，这样就保证了服务调用方的线程不被长时间，不必要地占用，从而避免了故障在分布式系统中的蔓延，乃至雪崩。

作用：

服务降级
服务器忙，请稍后再试，客户端一个友好提示（异常，超时等）
服务熔断
类比保险丝，达到最大服务访问后，直接拒绝访问，拉闸限电。然后调用服务降级的方法并返回友好提示
过程===》
服务的降级—->进而熔断—–>恢复调用的链路。
接近实时的监控
服务限流等
秒杀高并发等操作，严禁一窝蜂的过来拥挤，大家排队，一秒钟N个，有序进行。

编码模拟

创建cloud-provider-hystrix-paymant8001模块
导依赖

 <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>org.example</groupId>
            <artifactId>cloud-api-commons</artifactId>
            <version>${project.version}</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>
            <version>1.1.10</version>
        </dependency>

        <!--mysql-connector-java-->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
        </dependency>
        <!--jdbc-->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-jdbc</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <scope>runtime</scope>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.11</version>
            <scope>test</scope>
        </dependency>
    </dependencies>

yml

server:
  port: 8001

spring:
  application:
    name: cloud-provider-hystrix-payment
  datasource:
    type: com.alibaba.druid.pool.DruidDataSource            # 当前数据源操作类型
    driver-class-name: org.gjt.mm.mysql.Driver              # mysql驱动包
    url: jdbc:mysql://localhost:3306/db2019?useUnicode=true&characterEncoding=utf-8&useSSL=false
    username: root
    password: *******

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

主启动

@SpringBootApplication
@EnableEurekaClient
public class PaymentHystrixMain8001 {

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

}

service

package ink.awz.springcloud.service;

import org.springframework.stereotype.Service;

import java.util.concurrent.TimeUnit;

@Service
public class PaymentService {

    public String paymentInfo_OK(Integer id) {
        return "线程池：   "+Thread.currentThread().getName()+"paymentInfo_OK,id:  "+id+"\t"+"haha";
    }

    public String paymentInfo_TimeOut(Integer id) {
        try {
            TimeUnit.SECONDS.sleep(3);
        } catch (InterruptedException e) {
            throw new RuntimeException(e);
        }
        return "线程池：   "+Thread.currentThread().getName()+"paymentInfo_OK,id:  "+id+"\t"+"耗时3秒钟";
    }
}

controller

package ink.awz.springcloud.controller;

import ink.awz.springcloud.service.PaymentService;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RestController;

@RestController
@Slf4j
public class PaymentController {

    @Autowired
    private PaymentService paymentService;

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

    @GetMapping("/payment/hystrix/ok/{id}")
    public String paymentInfo_OK(@PathVariable("id") Integer id) {
        String result = paymentService.paymentInfo_OK(id);
        log.info("result"+result);
        return result;
    }

    @GetMapping("/payment/hystrix/timeOut/{id}")
    public String paymentInfo_timeOut(@PathVariable("id") Integer id) {
        String result = paymentService.paymentInfo_TimeOut(id);
        log.info("result"+result);
        return result;
    }
}