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1. 雪崩问题

一个微服务出现问题导致一系列微服务都不可以正常工作。
服务保护方案：

1. 请求限流。
2. 线程隔离。
   
3. 服务熔断
   

2. Sentinel

1. 启动Sentinel

java -Dserver.port=8090 -Dcsp.sentinel.dashboard.server=localhost:8090 -Dproject.name=sentinel-dashboard -jar sentinel-dashboard.jar

2. 依赖

<!--sentinel-->
<dependency><groupId>com.alibaba.cloud</groupId> <artifactId>spring-cloud-starter-alibaba-sentinel</artifactId>
</dependency>

3. 配置

spring:cloud: sentinel:transport:dashboard: localhost:8090http-method-specify: true # 将请求方式也作为簇点链路

簇点链路： Controller中的Rest接口

3. Fallback

1. 配置openfeign使之能够成为簇点链路

feign:okhttp:enabled: true # 开启OKHttp功能sentinel: # 让feign可以成为簇点链路enabled: true

2. 设置FallbackFactory

package com.hmall.api.client.fallback;import com.hmall.api.client.ItemClient;
import com.hmall.api.dto.ItemDTO;
import com.hmall.api.dto.OrderDetailDTO;
import com.hmall.common.utils.CollUtils;
import lombok.extern.slf4j.Slf4j;
import org.springframework.cloud.openfeign.FallbackFactory;import java.util.Collection;
import java.util.List;@Slf4j
public class ItemClientFallbackFactory implements FallbackFactory<ItemClient> {@Overridepublic ItemClient create(Throwable cause) {return new ItemClient() {@Overridepublic List<ItemDTO> queryItemByIds(Collection<Long> ids) {log.info("查询商品失败！", cause);return CollUtils.emptyList();}@Overridepublic void deductStock(List<OrderDetailDTO> items) {log.info("扣减商品库存失败!", cause);throw new RuntimeException(cause);}};}
}

3. 注册Bean

package com.hmall.api.config;import com.hmall.api.client.fallback.ItemClientFallbackFactory;
import com.hmall.common.utils.UserContext;
import feign.Logger;
import feign.RequestInterceptor;
import feign.RequestTemplate;
import org.springframework.context.annotation.Bean;public class DefaultFeignConfig {@Beanpublic Logger.Level feignLogLevel() {return Logger.Level.FULL;}@Beanpublic RequestInterceptor userInfoRequestInterceptor() {return new RequestInterceptor() {@Overridepublic void apply(RequestTemplate requestTemplate) {Long userId = UserContext.getUser();if (userId!=null) {requestTemplate.header("user-info", userId.toString());}}};}@Beanpublic ItemClientFallbackFactory itemClientFallbackFactory() {return new ItemClientFallbackFactory();}
}

4. 配置Bean

@FeignClient(value = "item-service", fallbackFactory = ItemClientFallbackFactory.class)
public interface ItemClient {@GetMapping("/items")List<ItemDTO> queryItemByIds(@RequestParam("ids") Collection<Long> ids);@PutMapping("/items/stock/deduct")void deductStock(@RequestBody List<OrderDetailDTO> items);
}

4. 熔断

拒绝发送请求给故障的微服务