Hystrix入門及使用

一、Hystrix簡介及功能

SpringCloud已經大大降低了我們各個服務之間的耦合性,但每個服務之間的調用卻緊密聯系,不可切斷,隨著分布式服務的數量增多,如果出現意外導致其中一個無法正常工作,會導致整個服務都停止,這顯然是不合理的.

Hystrix的出現能夠在某個依賴出問題的情況下,不導致整個服務失敗.也就是說相當于一個斷路器,通過監控斷路,返回一個符合預期,可處理的備選響應,而不是直接返回異常中斷或者長時間等待,增加分布式系統的彈性.

目前Hystrix已經停更,但其設計思想值得學習

Hystrix官方文檔

二、Hystrix重要概念

1.服務降級(fallback)

服務器忙,直接向客戶端拋出提示,請稍后再試,也就是一個兜底的處理方案

服務降級的情況:

• 程序運行異常
• 超時
• 服務熔斷
• 線程池/信號量打滿

2.服務熔斷(break)

服務器運載達到上限,拒絕客戶端訪問,然后進行服務降級,然后主見恢復服務

3.服務限流(flowlimit)

如果有高并發操作,對流量進行限制,進行排隊處理,防止服務器運載上限

三、Hystrix實現

1.構建子模塊

1.改pom

<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>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>
    <!--監控-->
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-actuator</artifactId>
    </dependency>
    <!--熱部署-->
    <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>

2.編寫yml

server:
  port: 8001

spring:
  application:
    name: cloud-provider-hystrix-payment
eureka:
  client:
    #表示向注冊中心注冊自己
    register-with-eureka: true
    #表明要從注冊中心中抓取自己的信息,集群必須要設置成true才能配合ribbon
    fetch-registry: true
    service-url:
      defaultZone: http://eureka7001.com:7001/eureka/

3.主方法啟動

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

    }
}

4.service層編寫

@Service
public class PaymentHystrixService {

    public String pamentInfo_OK(Integer id) {
        return "線程池:" + Thread.currentThread().getName() + "pamentInfo_OK,id=" + id + "\t" + "成功咯~~~~";
    }

    public String pamentInfo_TimeOut(Integer id) {
        int sleepTime = 3;
        try {
            TimeUnit.SECONDS.sleep(sleepTime);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        return "線程池:" + Thread.currentThread().getName() + "pamentInfo_TimeOut,id=" + id + "\t" + "小睡一會"+sleepTime+"秒成功咯~~~~";
    }
}

5.controller層編寫

@RestController
@Slf4j
public class PaymentHystrixController {

    @Resource
    private PaymentHystrixService paymentHystrixService;

    @GetMapping("/payment/hystrix/ok/{id}")
    public String pamentInfo_OK(@PathVariable Integer id) {
        return paymentHystrixService.pamentInfo_OK(id);
    }
    @GetMapping("/payment/hystrix/timeout/{id}")
    public String pamentInfo_TimeOut(@PathVariable Integer id) {
        return paymentHystrixService.pamentInfo_TimeOut(id);
    }

}

2.線程高壓測試

設置20000個線程形成高并發場景

本來不會卡頓的快速請求也變卡了.

也就是服務器中的所有線程被使用完了,導致只能等待.

1.加入消費者端

1.改pom

<dependencies>
    <dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-starter-openfeign</artifactId>
    </dependency>
    <!--eureka client-->
    <dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
    </dependency>
    <!--eureka client-->
    <dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-starter-netflix-hystrix</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>
    <!--監控-->
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-actuator</artifactId>
    </dependency>
    <!-- 引用自己定義的api通用包，可以使用Payment支付Entity -->
    <dependency>
        <groupId>com.xiaoxiao.springcloud</groupId>
        <artifactId>cloud-api-common</artifactId>
        <version>${project.version}</version>
    </dependency>
    <!--熱部署-->
    <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>

2.yml文件

server:
  port: 80
eureka:
  client:
    register-with-eureka: false
    service-url:
      defaultZone: http://localhost:7001/eureka/

3.主啟動類

@SpringBootApplication
@EnableHystrix
@EnableEurekaClient
public class HystrixOrderMain80 {
    public static void main(String[] args){
        SpringApplication.run(HystrixOrderMain80.class,args);

    }
}

4.編寫feign接口

@Component
@FeignClient(name = "CLOUD-PROVIDER-HYSTRIX-PAYMENT")
public interface OrderHystrixService {
    @GetMapping("/payment/hystrix/ok/{id}")
    public String pamentInfo_OK(@PathVariable Integer id);


    @GetMapping("/payment/hystrix/timeout/{id}")
    public String pamentInfo_TimeOut(@PathVariable Integer id) ;
}

5.編寫controller

@RestController
@Slf4j
public class OrderHystrixController {

    @Resource
    private OrderHystrixService orderHystrixService;

    @GetMapping("/consumer/payment/hystrix/ok/{id}")
    public String pamentInfo_OK(@PathVariable Integer id){
        return "我是消費者80"+orderHystrixService.pamentInfo_OK(id);
    }


    @GetMapping("/consumer/payment/hystrix/timeout/{id}")
    public String pamentInfo_TimeOut(@PathVariable Integer id) {
        return "我是消費者80"+orderHystrixService.pamentInfo_TimeOut(id);
    }
}

2.加入線程組

顯然,加入后80請求訪問也會非常卡

3.Hystrix應用

• 如果訪問對方服務器超時，調用者不能一直等待，需要服務降級
• 如果訪問服務器down機，調用者不能一直等待，需要進行服務降級
• 如果對方服務器OK，但是調用者自己出了故障，報錯或者是對時間反饋有要求但對方未達到，也需要進行服務降級

4.支付端服務降級

1.制定一個fallback備選方法

public String pamentInfo_TimeOutHandler(Integer id) {
    return "線程池:" + Thread.currentThread().getName() + "pamentInfo_TimeOut,id=" + id + "\t" + "我失敗了，請你返回一下謝謝";
}

2.設置降級配置

@Service
public class PaymentHystrixService {

    public String pamentInfo_OK(Integer id) {
        return "線程池:" + Thread.currentThread().getName() + "pamentInfo_OK,id=" + id + "\t" + "成功咯~~~~";
    }

    @HystrixCommand(fallbackMethod = "pamentInfo_TimeOutHandler", commandProperties = {
            @HystrixProperty(name="execution.isolation.thread.timeoutInMilliseconds",value="3000")
                    })
            public String pamentInfo_TimeOut(Integer id){

            int sleepTime = 5;
            try{
            TimeUnit.SECONDS.sleep(sleepTime);
            }catch(InterruptedException e) {
        e.printStackTrace();
    }
        return"線程池:"+Thread.currentThread().

    getName() +"pamentInfo_TimeOut,id="+id +"\t"+"小睡一會"+sleepTime+"秒成功咯~~~~";
}

    public String pamentInfo_TimeOutHandler(Integer id) {
        return "線程池:" + Thread.currentThread().getName() + "pamentInfo_TimeOut,id=" + id + "\t" + "我失敗了，請你返回一下謝謝";
    }
}

如果3秒沒有響應就服務降級,這里休眠5秒,所以降級了

同理,如果出現異常,也會進行服務降級處理,自動調動備選方法

5.消費端服務降級

1.改yml

feign:
  hystrix:
    enabled: true

開啟Hystrix支持

2.主方法加入@EnableHystrix

3.修改controller

@GetMapping("/consumer/payment/hystrix/timeout/{id}")
@HystrixCommand(fallbackMethod = "OrderTimeOutHandler", commandProperties = {
        @HystrixProperty(name = "execution.isolation.thread.timeoutInMilliseconds", value = "1500")
})
public String pamentInfo_TimeOut(@PathVariable("id") Integer id) {
    return "我是消費者80"+orderHystrixService.pamentInfo_TimeOut(id);
}


public String OrderTimeOutHandler(@PathVariable("id") Integer id) {
    return "我是消費者80:" + Thread.currentThread().getName() + "pamentInfo_TimeOut,id=" + id + "\t" + "我是消費端的降級!!!!";
}

6.設置默認fallback方法

需要服務降級要加@HystrixCommand注解,如果沒加fallback屬性,就找默認fallback,如果加了,就找指定的

@RestController
@Slf4j
@DefaultProperties(defaultFallback = "GlobalFallback")
public class OrderHystrixController {

    @Resource
    private OrderHystrixService orderHystrixService;

    @GetMapping("/consumer/payment/hystrix/ok/{id}")
    @HystrixCommand
    public String pamentInfo_OK(@PathVariable("id") Integer id) {
        return "我是消費者80" + orderHystrixService.pamentInfo_OK(id);
    }


    @GetMapping("/consumer/payment/hystrix/timeout/{id}")
/*    @HystrixCommand(fallbackMethod = "OrderTimeOutHandler", commandProperties = {
            @HystrixProperty(name = "execution.isolation.thread.timeoutInMilliseconds", value = "10000")
    })*/
    @HystrixCommand(commandProperties = {
            @HystrixProperty(name = "execution.isolation.thread.timeoutInMilliseconds", value = "10000")
    })
    public String pamentInfo_TimeOut(@PathVariable("id") Integer id) {
        return "我是消費者80" + orderHystrixService.pamentInfo_TimeOut(id);
    }


    public String OrderTimeOutHandler(@PathVariable("id") Integer id) {
        return "我是消費者80:" + Thread.currentThread().getName() + "pamentInfo_TimeOut,id=" + id + "\t" + "我是消費端的降級!!!!";
    }

    //全局fallback
    public String GlobalFallback() {
        return "我是消費者80:" + Thread.currentThread().getName() + "GlobalFallback,id=" + "\t" + "我是一個全局降級方法!!!!";
    }
}

7.實現feign接口類實現解耦

對于feign接口的每個方法,都需要一個fallback耦合度太高,而且如果對面服務器down機,會導致超時或不友善連接,這時候需要進行服務降級.具體方法就是使用一個類去實現feign接口然后標注為fallback類

@Component
@FeignClient(name = "CLOUD-PROVIDER-HYSTRIX-PAYMENT",fallback = OrderFeignFallbackService.class)
public interface OrderHystrixService {
    @GetMapping("/payment/hystrix/ok/{id}")
    public String pamentInfo_OK(@PathVariable("id") Integer id);


    @GetMapping("/payment/hystrix/timeout/{id}")
    public String pamentInfo_TimeOut(@PathVariable("id") Integer id) ;
}

@Component
public class OrderFeignFallbackService implements OrderHystrixService {
    @Override
    public String pamentInfo_OK(Integer id) {
        return "... OrderFeignFallbackService pamentInfo_OK,(┬＿┬)";
    }

    @Override
    public String pamentInfo_TimeOut(Integer id) {
        return "... OrderFeignFallbackService pamentInfo_TimeOut  (┬＿┬)";
    }
}

8.服務熔斷

當訪問服務器已經服務降級,并且還是繼續滿足服務降級的情況下,在一定失敗率的前提下回開啟服務熔斷,類似于電路圖中的開路,將本來閉合的電路變成開路,他也有一定的自我修復功能,就是保持一個"半開半閉的狀態",會在一定時間后放幾個信息過去,如果通過,又能回復到閉合.熔斷過程中是直接調用服務降級的fallback方法.

總而言之就是服務降級→到一定數量后服務熔斷→放出消息可用后關閉熔斷,恢復正常

1.服務層

@Service
public class PaymentHystrixService {

    public String pamentInfo_OK(Integer id) {
        return "線程池:" + Thread.currentThread().getName() + "pamentInfo_OK,id=" + id + "\t" + "成功咯~~~~";
    }

    @HystrixCommand(fallbackMethod = "pamentInfo_TimeOutHandler", commandProperties = {
            @HystrixProperty(name = "execution.isolation.thread.timeoutInMilliseconds", value = "5000")
    })
    public String pamentInfo_TimeOut(Integer id) {
//        int a = 10 / 0;
        int sleepTime = 1000;
        try {
            TimeUnit.MILLISECONDS.sleep(sleepTime);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        return "線程池:" + Thread.currentThread().

                getName() + "pamentInfo_TimeOut,id=" + id + "\t" + "小睡一會" + sleepTime + "秒成功咯~~~~";
    }

    public String pamentInfo_TimeOutHandler(Integer id) {
        return "線程池:" + Thread.currentThread().getName() + "pamentInfo_TimeOut,id=" + id + "\t" + "我失敗了，請你返回一下謝謝";
    }

    //=====服務熔斷
    @HystrixCommand(fallbackMethod = "paymentCircuitBreaker_fallback",commandProperties = {
            @HystrixProperty(name = "circuitBreaker.enabled",value = "true"),// 是否開啟斷路器
            @HystrixProperty(name = "circuitBreaker.requestVolumeThreshold",value = "10"),// 請求次數
            @HystrixProperty(name = "circuitBreaker.sleepWindowInMilliseconds",value = "10000"), // 時間窗口期
            @HystrixProperty(name = "circuitBreaker.errorThresholdPercentage",value = "60"),// 失敗率達到多少后跳閘
    })
    public String paymentCircuitBreaker(@PathVariable("id") Integer id)
    {
        if(id < 0)
        {
            throw new RuntimeException("******id 不能負數");
        }
        String serialNumber = IdUtil.simpleUUID();

        return Thread.currentThread().getName()+"\t"+"調用成功，流水號: " + serialNumber;
    }
    public String paymentCircuitBreaker_fallback(@PathVariable("id") Integer id)
    {
        return "id 不能負數，請稍后再試，/(ㄒoㄒ)/~~   id: " +id;
    }
}

2.controller層

//服務熔斷
@GetMapping("/payment/circuit/{id}")
public String paymentCircuitBreaker(@PathVariable("id") Integer id) {
    String result = paymentHystrixService.paymentCircuitBreaker(id);
    log.info("*****result:"+result);
    return result;
}

3.主方法加入注解

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

    }
}

//@EnableHystrix注解含有@EnableCircuitBreaker
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
@EnableCircuitBreaker
public @interface EnableHystrix {

}

9.Hystrix圖形化儀表盤搭建

1.新建模塊cloud-consumer-feign-hystrix-order80

2.修改pom文件

<dependencies>
    <dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-starter-netflix-hystrix-dashboard</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-actuator</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>
</dependencies>

3.編寫yml文件

server:
  port: 9001

4.編寫主方法

@SpringBootApplication
@EnableHystrixDashboard
public class HystrixDashboardMain9001 {
    public static void main(String[] args){
        SpringApplication.run(HystrixDashboardMain9001.class,args);      
        
    }
}

5.訪問地址

http://localhost:9001/hystrix

6.在被監控的模塊主方法下添加配置

老師說是舊版本的坑,否則會出現Unable to connect to Command Metric Stream的錯誤

/**
 *此配置是為了服務監控而配置，與服務容錯本身無關，springcloud升級后的坑
 *ServletRegistrationBean因為springboot的默認路徑不是"/hystrix.stream"，
 *只要在自己的項目里配置上下面的servlet就可以了
 */
@Bean
public ServletRegistrationBean getServlet() {
    HystrixMetricsStreamServlet streamServlet = new HystrixMetricsStreamServlet();
    ServletRegistrationBean registrationBean = new ServletRegistrationBean(streamServlet);
    registrationBean.setLoadOnStartup(1);
    registrationBean.addUrlMappings("/hystrix.stream");
    registrationBean.setName("HystrixMetricsStreamServlet");
    return registrationBean;
}

7.輸入被監控的網址

這里根據類來看是http://localhost:8001//hystrix.stream

四、總結

1.學習總結

Hystrix是一個能夠處理服務降級和服務熔斷的優秀框架，核心內容就是服務降級和服務熔斷，還有一個圖形化監控界面儀表盤。

一般是在服務響應超時，服務出現異常，或者是服務器滿負荷，或是服務器down機的情況下需要進行服務降級。服務熔斷是在一定百分比次數失敗訪問服務器出現服務降級進而會出現的功能，熔斷期間無法接受任何信息直接fallback，一段時間后會放幾個信息，如果成功則彈性恢復服務器。

2.注意事項

在HystrixCommandProperties記載了Hystrix的命令屬性

對于@HystrixCommand內屬性的修改,需要重啟微服務,不然有時候會有BUG,熱部署不會更新配置

3.疑惑

為什么在使用消費端調用服務端時設置value并不管用，設置了十秒也好，到了一秒如果服務端沒響應，直接返回timeout的fallback方法。那在hystrixcommand中設置的timevalue不是沒有意義了嗎？