一、Hystrix是什么

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，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，以提高分布式系统的弹性。

二、Hystrix能做什么

1、服务降级

服务器忙，请稍后再试，不让客户端等待并立刻返回一个友好提示fallback。

2、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。

3、服务限流

秒杀高并发等操作，严禁一窝蜂拥挤，大家排队，一秒钟N个，有序进行。

三、Hystrix怎么用

1、创建模块

创建普通maven模块cloud-provider-hystrix-payment8001

2、修改pom文件

<?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>cloud</artifactId> <groupId>com.shang.cloud</groupId> <version>1.0-SNAPSHOT</version> </parent> <modelVersion>4.0.0</modelVersion>

    <artifactId>cloud-provider-hystrix-payment8001</artifactId>

    <dependencies>
        <!--hystrix-->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-hystrix</artifactId>
        </dependency>
        <!--eureka client-->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
        </dependency>
        <!--web-->
        <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><!-- 引入自己定义的api通用包，可以使用Payment支付Entity -->
            <groupId>com.shang.cloud</groupId>
            <artifactId>cloud-api-commons</artifactId>
            <version>1.0-SNAPSHOT</version>
        </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>
    </dependencies>

    <properties>
        <maven.compiler.source>8</maven.compiler.source>
        <maven.compiler.target>8</maven.compiler.target>
    </properties>

</project>

3、编写yml文件

server:
port: 8001

spring:
application:
name: cloud-provider-hystrix-payment

eureka:
client:
register-with-eureka: true
fetch-registry: true
service-url:
\#集群版
\#defaultZone: <http://eureka7001.com:7001/eureka,http://eureka7002.com:7002/eureka>
\#单机版
defaultZone: <http://eureka7001.com:7001/eureka>

4、编写主启动类

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

5、编写逻辑代码

（1）service\

@Service
public class PaymentService {

/**
 * 正常访问，肯定OK
 * @param id
 * @return
 */
public String paymentInfo_OK(Integer id) {
    return "线程池:  "+Thread.currentThread().getName()+"  paymentInfo_OK,id:  "+id+"\t"+"O(∩_∩)O哈哈~";
}

public String paymentInfo_TimeOut(Integer id) {
    //int age = 10/0;
    try {
        TimeUnit.MILLISECONDS.sleep(3000);
    } catch (InterruptedException e) {
        e.printStackTrace();
    }
    return "线程池:  "+Thread.currentThread().getName()+" id:  "+id+"\t"+"O(∩_∩)O哈哈~"+"  耗时(秒): ";
}

}

（2）controller

@RestController
@Slf4j
public class PaymentController {

    @Autowired
    private PaymentService paymentService;

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

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

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

}