Hystrix服务容错之服务熔断

淡淡的烟草味﹌ 2023-01-04 14:43 307阅读 0赞

我们可以配置熔断策略，当请求出错比例在10s内大于50%时，该服务将进入熔断状态，后续请求都会进入fallbackMethod

然后会有一个重试策略，每隔一段时间会去看服务有没有恢复正常，如果服务恢复，则熔断状态关闭，否则继续进入fallbackMethod

实现方式：

增加依赖

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

接口实现类，@HystrixCommond注解来修饰需要熔断的方法，其中HystrixProperty中的参数，在HystriPropertiesManager类中可以找到对应的常量，主要参数都已列出，如果要模拟熔断，直接抛出RuntimeException

package com.qiangqiang.service.impl;
    
    
    import com.netflix.hystrix.contrib.javanica.annotation.HystrixCommand;
    import com.netflix.hystrix.contrib.javanica.annotation.HystrixProperty;
    import com.netflix.hystrix.contrib.javanica.conf.HystrixPropertiesManager;
    import com.qiangqiang.entity.Order;
    import com.qiangqiang.service.OrderService;
    import com.qiangqiang.service.ProductService;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.stereotype.Service;
    
    @Service
    public class OrderServiceImpl implements OrderService {
    
        @Autowired
        private ProductService productService;
    
        @HystrixCommand(
                commandProperties = {
                        //10s内请求大于10就启动熔断器，当符合熔断条件触发 fallbackMethod默认20个
                        @HystrixProperty(name= HystrixPropertiesManager.CIRCUIT_BREAKER_REQUEST_VOLUME_THRESHOLD,value = "10"),
                        //请求错误率大于50%就启动熔断器，然后for循环发起重试请求，当请求符合熔断条件触发fallbackMethod
                        @HystrixProperty(name=HystrixPropertiesManager.CIRCUIT_BREAKER_ERROR_THRESHOLD_PERCENTAGE,value = "50"),
                        //熔断多少秒后去重试请求，默认5s
                        @HystrixProperty(name=HystrixPropertiesManager.CIRCUIT_BREAKER_SLEEP_WINDOW_IN_MILLISECONDS,value = "5000")
                },
                fallbackMethod = "undertake1")        // 指定降级方法，在熔断和异常时会走降级方法
        @Override
        public Order getOrder(Integer id) {
            System.out.println(Thread.currentThread().getName()+"------------");
            if(id == 1){
                throw new RuntimeException("熔断了要");
            }
            Order order = new Order(1, "用户订单", 2, productService.getProductById(id));
            return order;
        }
    
    
        public Order undertake1(Integer id) {
            Order order = new Order(1, "用户订单兜底兜底", 2, productService.getProduct());
            return order;
        }
    
    
        @Override
        public Order getOrderById() {
            System.out.println(Thread.currentThread().getName()+"------------");
            Order order = new Order(1, "用户订单", 2, productService.getProduct());
            return order;
        }
    
        public Order undertake() {
            Order order = new Order(1, "用户订单兜底兜底", 2, productService.getProduct());
            return order;
        }
    
    
    }

最后，启动类要加上Hystrix注解

package com.qiangqiang;
    
    import org.springframework.boot.SpringApplication;
    import org.springframework.boot.autoconfigure.SpringBootApplication;
    import org.springframework.cloud.netflix.hystrix.EnableHystrix;
    import org.springframework.cloud.openfeign.EnableFeignClients;
    
    @SpringBootApplication
    @EnableFeignClients
    @EnableHystrix
    public class SpringCloudOrderServerHystrixApplication {
    
        public static void main(String[] args) {
            SpringApplication.run(SpringCloudOrderServerHystrixApplication.class, args);
        }
    
    }