SpringCloud之Hystrix的详细使用

目录

• ***一.服务降级***
• 2.不使用Hystrix的项目
• 3. 使用Hystrix
• 4. 全局的Hystrix配置
•  ***二.服务熔断***
• 1.熔断机制概述
• 2.项目中使用

1.概念

服务降级：服务器繁忙，请稍后再试，不让客户端等待，并立即返回一个友好的提示（一般发生在 程序异常，超时，服务熔断触发服务降级，线程池、信号量 打满也会导致服务降级）
服务熔断 ： 达到最大服务访问后，直接拒绝访问，然后调用服务降级的方法并返回友好提示（如保险丝一样）
服务限流 ： 秒杀等高并发操作，严禁一窝蜂的过来拥挤，排队进入，一秒钟N个，有序进行

***一.服务降级***

2.不使用Hystrix的项目

大致的Service和Controller层如下

***************Controller*****************
package com.sky.springcloud.controller;

import com.sky.springcloud.service.PaymentService;
import lombok.extern.slf4j.Slf4j;
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;
import javax.annotation.Resource;
@RestController
@Slf4j
public class PaymentController {
    @Resource
    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);
        return result;
    }
    @GetMapping("/payment/hystrix/timeout/{id}")
    public String paymentInfo_TimeOut(@PathVariable("id") Integer id){
        String result = paymentService.payment_Info_TimeOut(id);
}
*******************Service******************** 
package com.sky.springcloud.service;
import org.springframework.stereotype.Service;
import java.util.concurrent.TimeUnit;
@Service
public class PaymentServiceImpl implements PaymentService{
    @Override
    public String paymentInfo_ok(Integer id) {
        return "线程池：" + Thread.currentThread().getName() + "paymentInfo_Ok. id:" + id + "\t" + "~~~~~";
    public String payment_Info_TimeOut(Integer id) {
       try {
            TimeUnit.SECONDS.sleep(5);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        return "线程池：" + Thread.currentThread().getName() + "paymentInfo_TimeOut. id:" + id + "\t" + "~~~~~";

在这种情况时,当通过浏览器访问 TimeOut这个方法,会三秒后返回结果,而当访问 OK 这个方法时,会直接返回结果(但是这是在访问量很少的时候,一旦访问量过多,访问OK时也会出现延迟,这里可以使用Jmeter模拟两万个访问量,如下)

使用 Jmeter 模拟后,再去访问OK,会明显出现加载的效果

3. 使用Hystrix

在主启动类添加注解
@EnableHystrix

package com.sky.springcloud;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
import org.springframework.cloud.netflix.hystrix.EnableHystrix;
@SpringBootApplication
@EnableEurekaClient //启用Eureka
@EnableHystrix     //启用Hystrix
public class Payment8001 {
    public static void main(String[] args) {
        SpringApplication.run(Payment8001.class,args);
    }
}

在原有的基础上,在Service层加上如下注解

 @HystrixCommand(fallbackMethod = "payment_Info_TimeOutHandler",//当服务降级时,调用payment_Info_TimeOutHandler方法
                  commandProperties = {
            @HystrixProperty(name = "execution.isolation.thread.timeoutInMilliseconds",
            value = "3000")//设置时间为3秒,超过三秒就为时间超限

*****************改后的Service*******************
package com.sky.springcloud.service;

import com.netflix.hystrix.contrib.javanica.annotation.HystrixCommand;
import com.netflix.hystrix.contrib.javanica.annotation.HystrixProperty;
import org.springframework.stereotype.Service;

import java.util.concurrent.TimeUnit;
@Service
public class PaymentServiceImpl implements PaymentService{
    @Override
    public String paymentInfo_ok(Integer id) {
        return "线程池：" + Thread.currentThread().getName() + "paymentInfo_Ok. id:" + id + "\t" + "~~~~~";
    }

    @HystrixCommand(fallbackMethod = "payment_Info_TimeOutHandler",commandProperties = {
            @HystrixProperty(name = "execution.isolation.thread.timeoutInMilliseconds",value = "3000")
    })
    public String payment_Info_TimeOut(Integer id) {
      try {
            TimeUnit.SECONDS.sleep(5);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
      // int a = 10 / 0;
        return "线程池：" + Thread.currentThread().getName() + "paymentInfo_TimeOut. id:" + id + "\t" + "~~~~~";
    }
    public String payment_Info_TimeOutHandler(Integer id){
        return "线程超时或异常 " + Thread.currentThread().getName();
    }
}

如上Service所示,如果再次访问TimeOut需要等待五秒,但是Hystrix设置的超时时间为三秒,所以当三秒后没有结果就会服务降级,从而调用TimeOutHandler这个指定 的方法来执行(或者有程序出错等情况也会服务降级)

4. 全局的Hystrix配置

@DefaultProperties(defaultFallback = “Gloub_Test”)

package com.sky.springcloud.service;

import com.netflix.hystrix.contrib.javanica.annotation.DefaultProperties;
import com.netflix.hystrix.contrib.javanica.annotation.HystrixCommand;
import com.netflix.hystrix.contrib.javanica.annotation.HystrixProperty;
import org.springframework.stereotype.Service;
@Service
@DefaultProperties(defaultFallback = "Gloub_Test")
public class PaymentServiceImpl implements PaymentService{
    @Override
    @HystrixCommand
    public String paymentInfo_ok(Integer id) {
        int a = 10 / 0;
        return "线程池：" + Thread.currentThread().getName() + "paymentInfo_Ok. id:" + id + "\t" + "~~~~~";
    }
    @HystrixCommand(fallbackMethod = "payment_Info_TimeOutHandler",commandProperties = {
            @HystrixProperty(name = "execution.isolation.thread.timeoutInMilliseconds",value = "3000")
    })
    public String payment_Info_TimeOut(Integer id) {
   /*     try {
            TimeUnit.SECONDS.sleep(5);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }*/
        return "线程池：" + Thread.currentThread().getName() + "paymentInfo_TimeOut. id:" + id + "\t" + "~~~~~";
    public String payment_Info_TimeOutHandler(Integer id){
        return "线程超时或异常 " + Thread.currentThread().getName();
    public String Gloub_Test(){
        return "走了全局的";
}

如上Service所示,加了@HystrixCommand的方法里,
如果没指定fallbackMethod 就会默认去找全局的defaultFallback
这里 当paymentInfo_ok 方法出错时,会调用Gloub_Test方法
当payment_Info_TimeOut出错时,会调用payment_Info_TimeOutHandler方法

 ***二.服务熔断***

1.熔断机制概述

熔断机制是应对雪崩效应的一种微服务链路保护机制,当扇出链路的某个微服务出错不可用或者响应时间太长,会进行服务的降级,进而熔断该节点微服务的调用,快速返回错误的相应信息.当检测到该节点微服务调用相应正常后,恢复调用链路.

2.项目中使用

在上面的基础上,改写Service和Controller(添加以下代码)

//是否开启服务熔断(断路器)
 @HystrixProperty(name = "circuitBreaker.enabled",value = "true"),
 //服务请求的次数 
 @HystrixProperty(name = "circuitBreaker.requestVolumeThreshold",value = "10"),
 //时间的窗口期
 @HystrixProperty(name = "circuitBreaker.sleepWindowInMilliseconds", value = "10000"),
 //当失败率达到多少后发生熔断
 @HystrixProperty(name = "circuitBreaker.errorThresholdPercentage",value = "60"), 

******************Service*****************
    @HystrixCommand(fallbackMethod = "paymentCircuitBreaker_fallback",
                    commandProperties = {
                    @HystrixProperty(name = "circuitBreaker.enabled",value = "true"),
                    @HystrixProperty(name = "circuitBreaker.requestVolumeThreshold",value = "10"),
                    @HystrixProperty(name = "circuitBreaker.sleepWindowInMilliseconds", value = "10000"),
                    @HystrixProperty(name = "circuitBreaker.errorThresholdPercentage",value = "60"),
                    })
    public String PaymentCircuitBreaker(@PathVariable("id") Integer id){
        if(id<0){
            throw new RuntimeException("********** id不能为负");
        }
        String serialNumber = IdUtil.simpleUUID();
        return Thread.currentThread().getName() + "\t" + serialNumber;
    }
    public String paymentCircuitBreaker_fallback(@PathVariable("id") Integer id){
        return  "id 不能为负:" + id;
************Controller********************
    @GetMapping("/payment/circuit/{id}")
        String result = paymentService.PaymentCircuitBreaker(id);
        log.info(result + "***********");
        return result;

如上所示,当访问paymentCircuitBreaker时,如果id小于零则会有一个运行错误,这时候就会通过服务降级来调用paymentCircuitBreaker_fallback方法,当错误的次数达到60%的时候(自己设的),就会出现服务熔断,这个时候再访问id大于零的情况,也会发生服务降级,因为开起了服务熔断,需要慢慢的恢复正常.

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