所謂降級,就是當某個服務出現異常以後,服務器將再也不被調用,此時服務端能夠本身準備一個本地的fallback回調,返回一個缺省值。
這樣作,雖然服務水平降低,但好歹可用,比直接掛掉要強,固然這也要看適合的業務場景。java
啓動類:web
package com.wangfajun; import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; import org.springframework.cloud.client.SpringCloudApplication; import org.springframework.cloud.client.circuitbreaker.EnableCircuitBreaker; import org.springframework.cloud.client.discovery.EnableDiscoveryClient; //@SpringBootApplication //@EnableDiscoveryClient //@EnableCircuitBreaker //開啓斷路器 @SpringCloudApplication public class FajunClientTestApplication { public static void main(String[] args) { SpringApplication.run(FajunClientTestApplication.class, args); } }
服務端代碼demo(客戶端請求服務端serverMethod方法時,若是服務端宕機或是serverMethod中拋出異常,則將調用defaultFallback方法):spring
package com.odao.client.controller; import com.netflix.hystrix.contrib.javanica.annotation.DefaultProperties; import com.netflix.hystrix.contrib.javanica.annotation.HystrixCommand; import org.springframework.web.bind.annotation.*; @RestController @DefaultProperties(defaultFallback = "defaultFallback") public class FeignClientTestController { @HystrixCommand @GetMapping(value = "serverMethod") public String serverMethod() {
/*throw new RuntimeException("異常了");*/
return null;
}
public String defaultFallback() {
return "太擁擠了";
}
pom:服務器
<!--hystrix--> <dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-starter-hystrix</artifactId> </dependency>