Spring Cloud（十一）Hystrix 服务降级、熔断

系统管理员 2022-11-25 10:12 164阅读 0赞

**Table of Contents**

1.Hystrix 介绍

2.pom.xml中添加依赖

3.服务降级

降级在提供者（provider-hystrix-payment8007）

降级在消费者（consumer-feign-hystrix-order80）

全局服务降级

4.服务熔断

5.工作流程

6.hystrix dashboard监控

7.hystrix + turbine 集群聚合监控

--------------------

## 1.Hystrix 介绍 ##

[https://github.com/Netflix/Hystrix/wiki][https_github.com_Netflix_Hystrix_wiki]

在分布式环境中，许多服务依赖项中的一些必然会失败。Hystrix是一个库，通过添加延迟容忍和容错逻辑，帮助你控制这些分布式服务之间的交互。Hystrix通过隔离服务之间的访问点、停止级联失败和提供回退选项来实现这一点，所有这些都可以提高系统的整体弹性。

在springcloud中断路器组件就是Hystrix。Hystrix也是Netflix套件的一部分。他的功能是，当对某个服务的调用在一定的时间内（默认10s），有超过一定次数（默认20次）并且失败率超过一定值（默认50%），该服务的断路器会打开。返回一个由开发者设定的fallback。

Hystrix被设计的目标是：

1.  对通过第三方客户端库访问的依赖项（通常是通过网络）的延迟和故障进行保护和控制。
2.  在复杂的分布式系统中阻止级联故障。
3.  快速失败，快速恢复。
4.  回退，尽可能优雅地降级。
5.  启用近实时监控、警报和操作控制。

## 2.pom.xml中添加依赖 ##

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

## 3.**服务降级** ##

**三种情况：**

1.  访问超时
2.  运行错误
3.  宕机

### **降级在提供者（provider-hystrix-payment8007）** ###

@EnableCircuitBreaker
    @EnableEurekaClient
    @SpringBootApplication
    public class Payment8007 {
        public static void main(String[] args) {
            SpringApplication.run(Payment8007.class,args);
        }
    }

@Service
    public class PaymentServiceImpl implements PaymentService {
    
        /**
         * 访问超时
         *
         * @param id
         * @return
         */
        @HystrixCommand(fallbackMethod = "paymentInfo_TimeOutHandler", commandProperties = {
                @HystrixProperty(name = "execution.isolation.thread.timeoutInMilliseconds", value = "3000")
        })
        public String paymentInfo_TimeOut(Integer id) {
            int timeNumber = 5;
            try {
                TimeUnit.SECONDS.sleep(timeNumber);
            } catch (Exception e) {
                e.printStackTrace();
            }
            return "线程池：" + Thread.currentThread().getName() + "paymentinfo_Timeout,id:" + id + "\t" + "耗时(秒)" + timeNumber;
        }
    
        private String paymentInfo_TimeOutHandler(Integer id) {
            return "线程池：" + Thread.currentThread().getName() + "paymentInfo_TimeOutHandler,id:" + id + "\t";
        }
    }

### **降级在消费者（consumer-feign-hystrix-order80）** ###

**application.yml**

feign:
      hystrix:
        enabled: true

@EnableHystrix
    @EnableEurekaClient
    @EnableFeignClients
    @SpringBootApplication
    public class OrderFeignHystrix80 {
        public static void main(String[] args) {
            SpringApplication.run(OrderFeignHystrix80.class,args);
        }
    }

@Slf4j
    @RestController
    @RequestMapping("/order/payment")
    public class OrderPaymentController {
    
        @Autowired
        private PaymentFeignService paymentFeignService;
    
        @GetMapping("paymentInfo_TimeOut/{id}")
        @HystrixCommand(fallbackMethod = "paymentInfo_TimeOutHandler", commandProperties = {
                @HystrixProperty(name = "execution.isolation.thread.timeoutInMilliseconds", value = "1500")
        })
        public String paymentInfo_TimeOut(@PathVariable Integer id) {
            return paymentFeignService.paymentInfo_TimeOut(id);
        }
    
        private String paymentInfo_TimeOutHandler(Integer id) {
            return "OrderPayment 线程池：" + Thread.currentThread().getName() + "paymentInfo_TimeOutHandler,id:" + id + "\t";
        }
    }

**或者**

@Primary
    @FeignClient(value = "PAYMENT-SERVICE2",fallback = PaymentFeignService2.PaymentFeignService2FallBack.class)//模拟不存在的服务，宕机
    public interface PaymentFeignService2 {
    
        @GetMapping("payment/paymentInfo_TimeOut/{id}")
        String paymentInfo_TimeOut(@PathVariable("id") Integer id);
    
        @Component
        class PaymentFeignService2FallBack implements PaymentFeignService2{
    
            @Override
            public String paymentInfo_TimeOut(Integer id) {
                return "PAYMENT-SERVICE2 宕机";
            }
        }
    }

### **全局服务降级** ###

**问题：**

1、每个方法有一个对应的处理方法，代码膨胀。

2、处理方法和主业务逻辑混合在一起

**解决方案：**

@DefaultProperties(defaultFallback="")

类上加上注解：

默认全局处理方法

@HystrixCommand//不加属性代表使用默认的全局处理方法。

@DefaultProperties(defaultFallback = "payment_Global_FallbackMethod")
    @Slf4j
    @RestController
    @RequestMapping("/order/payment")
    public class OrderPaymentController {
    
        @Autowired
        private PaymentFeignService paymentFeignService;
    
        @GetMapping("paymentInfo_TimeOut/{id}")
    //    @HystrixCommand(fallbackMethod = "paymentInfo_TimeOutHandler", commandProperties = {
    //            @HystrixProperty(name = "execution.isolation.thread.timeoutInMilliseconds", value = "1500")
    //    })
        @HystrixCommand
        public String paymentInfo_TimeOut(@PathVariable Integer id) {
            return paymentFeignService.paymentInfo_TimeOut(id);
        }
    
        private String paymentInfo_TimeOutHandler(Integer id) {
            return "OrderPayment 线程池：" + Thread.currentThread().getName() + "paymentInfo_TimeOutHandler,id:" + id + "\t";
        }
    
        private String payment_Global_FallbackMethod() {
            return "全局 线程池：" + Thread.currentThread().getName() + "paymentInfo_TimeOutHandler";
        }

## 4.**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：

**服务的降级->进而熔断->恢复调用链路**

**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响应时间太长时,会进行服务的降级,进而熔断该节点微服务的调用,快速返回错误的响应信息。当检测到该节点微服务调用响应正常后,恢复调用链路。

在Spring Cloud框架里,熔断机制通过Hystrix实现. Hystrix会监控微服务间调用的状况,当失败的调用到一定阈值,缺省是5秒内20次调用失败,就会启动熔断机制,熔断机制的注解是@HystrixCommand.

//====服务熔断
    
        /**
         * 在10秒窗口期中10次请求有6次是请求失败的,断路器将起作用
         *
         * @param id
         * @return
         */
        @HystrixCommand(
                fallbackMethod = "paymentCircuitBreaker_fallback", commandProperties = {
                @HystrixProperty(name = "circuitBreaker.enabled", value = "true"),// 是否开启断路器
                @HystrixProperty(name = "circuitBreaker.requestVolumeThreshold", value = "10"),// 请求次数
                @HystrixProperty(name = "circuitBreaker.sleepWindowInMilliseconds", value = "10000"),// 时间窗口期
                @HystrixProperty(name = "circuitBreaker.errorThresholdPercentage", value = "60")// 失败率达到多少后跳闸
        }
        )
        public String paymentCircuitBreaker(Integer id) {
            if (id < 0) {
                throw new RuntimeException("*****id不能是负数");
            }
            String serialNumber = IdUtil.simpleUUID();
            return Thread.currentThread().getName() + "\t" + "调用成功,流水号:" + serialNumber;
        }
    
        private String paymentCircuitBreaker_fallback(Integer id) {
            String serialNumber = IdUtil.simpleUUID();
            return "id 不能负数,请稍后重试,o(╥﹏╥)o id:" + id+" 流水号:" + serialNumber;
        }

Hystrix断路器常用的三个重要指标参数

1、circuitBreaker.requestVolumeThreshold

> 断路器的窗口期内触发断路的请求阈值，默认为**20**。换句话说，假如某个窗口期内的请求总数都不到该配置值，那么断路器连发生的资格都没有。断路器在该窗口期内将不会被打开。

2、circuitBreaker.sleepWindowInMilliseconds

> 断路器的快照时间窗，也叫做窗口期。可以理解为一个触发断路器的周期时间值，默认为**10秒（10000）**。

3、circuitBreaker.errorThresholdPercentage

> 断路器的窗口期内能够容忍的错误百分比阈值，默认为**50（也就是说默认容忍50%的错误率）**。打个比方，假如一个窗口期内，发生了100次服务请求，其中50次出现了错误。在这样的情况下，断路器将会被打开。在该窗口期结束之前，即使第51次请求没有发生异常，也将被执行fallback逻辑。

综上所述，在以上三个参数缺省的情况下，Hystrix断路器触发的默认策略为：

> 在10秒内，发生20次以上的请求时，假如错误率达到50%以上，则断路器将被打开。（当一个窗口期过去的时候，断路器将变成半开（HALF-OPEN）状态，如果这时候发生的请求正常，则关闭，否则又打开）

## 5.工作流程 ##

[https://github.com/Netflix/Hystrix/wiki/How-it-Works][https_github.com_Netflix_Hystrix_wiki_How-it-Works]

1.  Construct a HystrixCommand or HystrixObservableCommand Object
2.  Execute the Command
3.  Is the Response Cached?
4.  Is the Circuit Open?
5.  Is the Thread Pool/Queue/Semaphore Full?
6.  HystrixObservableCommand.construct() or HystrixCommand.run()
7.  Calculate Circuit Health
8.  Get the Fallback
9.  Return the Successful Response

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjAzMjE5OQ_size_16_color_FFFFFF_t_70][]

## 6.hystrix dashboard监控 ##

服务 consumer-hystrix-dashboard8020

<dependencies>
            
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-starter-netflix-hystrix-dashboard</artifactId>
            </dependency>
            <dependency>
                <groupId>com.ak.demo</groupId>
                <artifactId>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.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>
            </dependency>
        </dependencies>

@EnableHystrixDashboard
    @SpringBootApplication
    public class HystrixDashboard8020 {
        public static void main(String[] args) {
            SpringApplication.run(HystrixDashboard8020.class, args);
        }
    }

被监控的服务provider-hystrix-payment8007 要包含：

<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>

启动类：@EnableCircuitBreaker

application.yml 暴露 `hystrix.stream` 端点

management:
      endpoints:
        web:
          exposure:
            include: hystrix.stream

访问[http://localhost:8007/actuator/][http_localhost_8007_actuator] 确保含有：[http://localhost:8007/actuator/hystrix.stream][http_localhost_8007_actuator_hystrix.stream]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjAzMjE5OQ_size_16_color_FFFFFF_t_70 1][]

访问地址：[http://localhost:8020/hystrix][http_localhost_8020_hystrix]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjAzMjE5OQ_size_16_color_FFFFFF_t_70 2][]

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## 7.hystrix + turbine 集群聚合监控 ##

hystrix dashboard 一次只能监控一个服务实例，使用 turbine 可以汇集监控信息，将聚合后的信息提供给 hystrix dashboard 来集中展示和监控。

**consumer-hystrix-turbine8021**

<dependencies>
            
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-starter-netflix-turbine</artifactId>
            </dependency>
            
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
            </dependency>
            <dependency>
                <groupId>com.ak.demo</groupId>
                <artifactId>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.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>
            </dependency>
        </dependencies>

server:
      port: 8021
    
    spring:
      application:
        name: hystrix-turbine-service
    eureka:
      client:
        service-url:
          defaultZone: http://eureka7001.com:7001/eureka/
    
    turbine:
      app-config: PAYMENT-SERVICE
      cluster-name-expression: new String("default")

**添加 `@EnableTurbine` 和 `@EnableDiscoveryClient` 注解**

@EnableTurbine
    @EnableDiscoveryClient
    @SpringBootApplication
    public class HystrixTurbine8021 {
        public static void main(String[] args) {
            SpringApplication.run(HystrixTurbine8021.class,args);
        }
    }

*  **turbine 监控路径：[http://localhost:8021/turbine.stream][http_localhost_8021_turbine.stream]**

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjAzMjE5OQ_size_16_color_FFFFFF_t_70 5][]

*  **在 hystrix dashboard 中填入turbine 监控路径，开启监控：[http://localhost:8020/hystrix][http_localhost_8020_hystrix 1]**

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjAzMjE5OQ_size_16_color_FFFFFF_t_70 6][]

*  **turbine聚合了 **PAYMENT-SERVICE **两台服务器的hystrix监控信息**

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjAzMjE5OQ_size_16_color_FFFFFF_t_70 7][]

[https_github.com_Netflix_Hystrix_wiki]: https://github.com/Netflix/Hystrix/wiki
[https_github.com_Netflix_Hystrix_wiki_How-it-Works]: https://github.com/Netflix/Hystrix/wiki/How-it-Works
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[http_localhost_8007_actuator]: http://localhost:8007/actuator/
[http_localhost_8007_actuator_hystrix.stream]: http://localhost:8007/actuator/hystrix.stream
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjAzMjE5OQ_size_16_color_FFFFFF_t_70 1]: /images/20221124/1cb39ed93ffe4cca95b7db1eff30cf5a.png
[http_localhost_8020_hystrix]: http://localhost:8020/hystrix
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjAzMjE5OQ_size_16_color_FFFFFF_t_70 2]: /images/20221124/f63357cbd33c4eb3adac9eab3cce735b.png
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[http_localhost_8021_turbine.stream]: http://localhost:8021/turbine.stream
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[http_localhost_8020_hystrix 1]: http://localhost:4001/hystrix
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