Hystrix原理及使用

背景介绍

1. 服务雪崩

分布式系统环境下，服务间类似依赖非常常见，一个业务调用通常依赖多个基础服务。

一个服务失败，导致整条链路的服务都失败的情形，我们称之为服务雪崩

2.引起服务雪崩和服务雪崩的三个阶段

原因大致有四：

硬件故障

程序bug

缓存击穿（用户大量访问缓存中没有键值，导致大量请求数据库，使数据库压力过大）

用户大量请求

服务雪崩的第一阶段：

服务不可用

调用端重试加大流量

服务调用者不可用

3.解决方案

应用扩容（加机器；升级硬件）

流量控制（限流；关闭重试）

缓存（将用户可能大量访问的数据放入缓存，减少数据库压力）

服务降级

服务接口拒绝服务
页面拒绝服务
延迟持久化
随机拒绝服务

服务熔断

入门

Hystrix是一个用于处理分布式系统延期和容错的开源库，Hystrix能保证在一个依赖出问题的情况下，不会导致整体服务失败，提高分布式弹性。

服务降级：假设对方系统不可用了，向调用方返回一个符合预期的，可处理的备选响应，而不是长时间等待或者抛出无处理的异常。这样就保证了服务方的线程不会被长时间不必要的占用，从而避免故障在分布式系统中蔓延，乃至雪崩。

服务熔断：达到最大访问后直接拒绝访问

服务限流：秒杀高并发等操作，排队有序进行

代码

1.没有引入hystrix的准备工作

建这三个工程模拟Hystrix服务降级

EurekaMain7001代码：

pom:

        <!--Eureka server-->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
        </dependency>

yml:

server:
  port: 7001

eureka:
  instance:
    hostname: eureka7001.com
  client:
    #表示不往注册中心注册自己
    register-with-eureka: false
    #表示自己端就是注册中心，我的职责就是维护实例
    fetch-registry: false
    #设置地址
    service-url:
      defaultZone: http://eureka7001.com:7001/eureka/

主启动类：

@SpringBootApplication
@EnableEurekaServer
public class EurekaMain7001 {
    public static void main(String[] args) {
        SpringApplication.run(EurekaMain7001.class, args);
    }
}

HystrixPaymentMain8001代码：

pom：

        <!--Eureka server-->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
        </dependency>

yml:

server:
  port: 8001

spring:
  application:
    name: cloud-payment-hystrix-service
eureka:
  client:
    register-with-eureka: true
    fetch-registry: true
    service-url:
      defaultZone: http://localhost:7001/eureka/
  instance:
    instance-id: hystrix-payment8001
    prefer-ip-address: true

service层：

@Service
public class HystrixPaymentService {
    public String getPaymentInfoSuccess() {
        return "thread poor: " + Thread.currentThread().getName() + " success";
    }

    public String getPaymentInfoTimeout() {
        try {
            int spendTime = 3000;
            TimeUnit.MILLISECONDS.sleep(spendTime);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        return "thread poor: " + Thread.currentThread().getName() + " timeout";
    }
}

controller:

@RestController
@Slf4j
public class HystrixPaymentController {
    @Resource
    HystrixPaymentService service;

    @GetMapping("/payment/hystrix/ok")
    public String getPaymentInfoSuccess() {
        return service.getPaymentInfoSuccess();
    }

    @GetMapping("/payment/hystrix/timeout")
    public String getPaymentInfoTimeout() {
        return service.getPaymentInfoTimeout();
    }
}

主启动类：

@SpringBootApplication
@EnableEurekaClient
public class HystrixPaymentMain8001 {
    public static void main(String[] args) {
        SpringApplication.run(HystrixPaymentMain8001.class, args);
    }
}

HystrixOrderMain80代码：

pom:

        <!-- open feign -->
        <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>

yml:

server:
  port: 80

spring:
  datasource:
    type: com.alibaba.druid.pool.DruidDataSource
    driver-class-name: org.gjt.mm.mysql.Driver
    url: jdbc:mysql://localhost:3306/db2021?useUnicode=true&characterEncoding=utf-8&useSSL=false
    username: root
    password: root

eureka:
  client:
    register-with-eureka: false
    service-url:
      defaultZone: http://eureka7001.com:7001/eureka/

ribbon:
  ReadTimeout: 5000
  ConnectTimeout: 5000

service接口：

@Component
@FeignClient(value = "CLOUD-PAYMENT-HYSTRIX-SERVICE")
public interface HystrixService {
    @GetMapping("/payment/hystrix/ok")
    public String getPaymentInfoSuccess();
    @GetMapping("/payment/hystrix/timeout")
    public String getPaymentInfoTimeout();
}

controller:

@RestController
public class HystrixController {
    @Resource
    private HystrixService hystrixService;

    @GetMapping("/consumer/payment/hystrix/ok")
    public String getPaymentInfoSuccess() {
        return hystrixService.getPaymentInfoSuccess();
    }
    @GetMapping("/consumer/payment/hystrix/timeout")
    public String getPaymentInfoFail() {
        return hystrixService.getPaymentInfoTimeout();
    }
}

主启动类：

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

到此，payment注册到eureka, order用openFeign调用payment过程已经完成。

2.压力测试

用jmeter两万个线程调用timeout接口，再通过chrome访问ok接口，会发现chrome访问的ok接口也会响应过慢。

ok接口也会出现调用过慢，转圈圈

解决1：在服务端（payment8001）熔断降级：

service上：

@Service
public class HystrixPaymentService {
    public String getPaymentInfoSuccess() {
        return "thread poor: " + Thread.currentThread().getName() + " success";
    }

    @HystrixCommand(fallbackMethod = "timeoutHandler", commandProperties = {
            @HystrixProperty(name = "execution.isolation.thread.timeoutInMilliseconds",value="2000")
    })
    public String getPaymentInfoTimeout() {
        try {
            int spendTime = 5000;
            TimeUnit.MILLISECONDS.sleep(spendTime);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        return "thread poor: " + Thread.currentThread().getName() + " timeout";
    }

    public String timeoutHandler() {
        return "call back fail";
    }
}

主程序类上：

@SpringBootApplication
@EnableEurekaClient
@EnableCircuitBreaker
public class HystrixPaymentMain8001 {
    public static void main(String[] args) {
        SpringApplication.run(HystrixPaymentMain8001.class, args);
    }
}

引入pom以解决找不到@HystrixCommand注解问题

        <!--解决@HystrixCommand注解找不到问题-->
        <dependency>
            <groupId>com.netflix.hystrix</groupId>
            <artifactId>hystrix-javanica</artifactId>
            <version>RELEASE</version>
        </dependency>

对payment8001进行测试，超时异常时，熔断降级测试成功：

再试一下运行异常：

    @HystrixCommand(fallbackMethod = "timeoutHandler", commandProperties = {
            @HystrixProperty(name = "execution.isolation.thread.timeoutInMilliseconds",value="2000")
    })
    public String getPaymentInfoTimeout() {
        int i = 10/0;
        return "thread poor: " + Thread.currentThread().getName() + " timeout";
    }

    public String timeoutHandler() {
        return "call back fail";
    }

熔断降级测试也能成功：

解决2：在客户端（order80）熔断降级：

准备工作：先修改HystrixOrderMain80里的超时时间，使直接调用不会超时：

@Service
public class HystrixPaymentService {
    public String getPaymentInfoSuccess() {
        return "thread poor: " + Thread.currentThread().getName() + " success";
    }

    @HystrixCommand(fallbackMethod = "timeoutHandler", commandProperties = {
            @HystrixProperty(name = "execution.isolation.thread.timeoutInMilliseconds",value="5000")
    })
    public String getPaymentInfoTimeout() {
        try {
            TimeUnit.MILLISECONDS.sleep(3000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        return "thread poor: " + Thread.currentThread().getName() + " timeout";
    }

    public String timeoutHandler() {
        return "call back fail";
    }
}

在cloud-consumer-hystrix-order80里添加代码：

pom:

        <!--解决@HystrixCommand注解找不到问题-->
        <dependency>
            <groupId>com.netflix.hystrix</groupId>
            <artifactId>hystrix-javanica</artifactId>
            <version>RELEASE</version>
        </dependency>

yml:

feign:
  hystrix:
    enabled: true

主程序：

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

controller:

@RestController
public class HystrixController {
    @Resource
    private HystrixService hystrixService;

    @GetMapping("/consumer/payment/hystrix/ok")
    public String getPaymentInfoSuccess() {
        return hystrixService.getPaymentInfoSuccess();
    }

    @GetMapping("/consumer/payment/hystrix/timeout")
    @HystrixCommand(fallbackMethod = "orderTimeoutHandler", commandProperties = {
            @HystrixProperty(name = "execution.isolation.thread.timeoutInMilliseconds",value="1000")
    })
    public String getPaymentInfoFail() {
        return hystrixService.getPaymentInfoTimeout();
    }

    public String orderTimeoutHandler() {
        return "order timeout handler...";
    }
}

测试：

1.调用服务端接口，不会超时：

2.调用消费端接口，出现了熔断降级，验证成功：

全局服务降级处理：

@RestController
@DefaultProperties(defaultFallback = "globalFallBackMethod")
public class HystrixController {
    @Resource
    private HystrixService hystrixService;

    @GetMapping("/consumer/payment/hystrix/ok")
    @HystrixCommand
    public String getPaymentInfoSuccess() {
        int i = 10/0;
        return hystrixService.getPaymentInfoSuccess();
    }

    @GetMapping("/consumer/payment/hystrix/timeout")
    @HystrixCommand(fallbackMethod = "orderTimeoutHandler", commandProperties = {
            @HystrixProperty(name = "execution.isolation.thread.timeoutInMilliseconds",value="1000")
    })
    public String getPaymentInfoFail() {
        return hystrixService.getPaymentInfoTimeout();
    }

    public String orderTimeoutHandler() {
        return "order timeout handler...";
    }

    public String globalFallBackMethod() {
        return "global fallback handler...";
    }
}

测试全局异常熔断ok：

所以，如果是全局的就加@DefaultProperties(defaultFallback = "globalFallBackMethod") 和@HystrixCommand注解，如果有需要单独的fallback的就加

   @HystrixCommand(fallbackMethod = "orderTimeoutHandler", commandProperties = {
            @HystrixProperty(name = "execution.isolation.thread.timeoutInMilliseconds",value="1000")
    })

在消费端这样添加代码会有冗余重复等现象。所以改进一下，在Feign上添加callback：

@Component
@FeignClient(value = "CLOUD-PAYMENT-HYSTRIX-SERVICE", fallback = HystrixServiceImpl.class)
public interface HystrixService {
    @GetMapping("/payment/hystrix/ok")
    public String getPaymentInfoSuccess();
    @GetMapping("/payment/hystrix/timeout")
    public String getPaymentInfoTimeout();
}

添加一个实现类：

@Service
public class HystrixServiceImpl implements HystrixService {
    @Override
    public String getPaymentInfoSuccess() {
        return "HystrixServiceImpl ok fallback  ... ";
    }

    @Override
    public String getPaymentInfoTimeout() {
        return "HystrixServiceImpl timeout fallback ... ";
    }
}

#controller上面不用加@HystrixCommand，只在service层加代码即可

关闭服务提供端（payment8001)再测试成功：

posted @ 2021-05-26 18:13 圣金巫灵阅读(427) 评论(0) 编辑收藏举报

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