简介
在微服务架构中,微服务之间的依赖关系错综复杂,难免的某些服务会出现故障,导致服务调用方出现远程调度的线程阻塞。在高负载的场景下,如果不做任何处理,可能会引起级联故障,导致服务调用方的资源耗尽甚至整个系统奔溃。Hystrix是一个由Netflix开源的一个延迟和容错库,它通过添加延迟容忍和容错逻辑来帮助控制这些微服务之间的交互。Hystrix通过隔离服务之间的访问点、停止跨服务的级联故障并提供回退选项来实现这一点,所有这些选项都提高了系统的总体弹性。
项目介绍
- sc-parent,父模块(请参照)
- sc-eureka,注册中心(请参照)
- sc-provider,提供者(请参照)
- sc-consumer-hystrix-ribbon,使用Hystrix+Ribbon的消费者
- sc-consumer-hystrix-feign,使用Hystrix+Feign的消费者
在Ribbon上使用Hystrix
1.在父模块下创建子模块项目sc-consumer-hystrix-ribbon,pom.xml:
4.0.0 com.cf sc-parent 0.0.1-SNAPSHOT sc-consumer-hystrix-ribbon org.springframework.cloud spring-cloud-starter-netflix-eureka-client org.springframework.cloud spring-cloud-starter-netflix-hystrix
2.创建启动类consumer.ConsumerApplication:
package consumer;import org.springframework.boot.SpringApplication;import org.springframework.boot.autoconfigure.SpringBootApplication;import org.springframework.cloud.client.circuitbreaker.EnableCircuitBreaker;import org.springframework.cloud.client.loadbalancer.LoadBalanced;import org.springframework.context.annotation.Bean;import org.springframework.web.client.RestTemplate;@SpringBootApplication@EnableCircuitBreakerpublic class ConsumerApplication { public static void main(String[] args) { SpringApplication.run(ConsumerApplication.class, args); } //为RestTemplate整合Ribbon,使其具备负载均衡的能力 @LoadBalanced @Bean public RestTemplate restTemplate(){ return new RestTemplate(); }}
3.创建调用提供者服务的Controller:consumer.controller.ConsumerController
package consumer.controller;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.web.bind.annotation.GetMapping;import org.springframework.web.bind.annotation.RestController;import org.springframework.web.client.RestTemplate;import com.netflix.hystrix.contrib.javanica.annotation.HystrixCommand;@RestControllerpublic class ConsumerController { @Autowired private RestTemplate restTemplate; @HystrixCommand(fallbackMethod="getBookListFallBack") @GetMapping("/getBookList") public String getBookList(){ return restTemplate.getForObject("http://sc-provider/book/list", String.class); } public String getBookListFallBack(){ return "[\"Java入门到放弃\"]"; }}
@HystrixCommand:表示将getBookList方法作为hystrix命令调用的方法。
fallbackMethod:指定处理回退逻辑的方法,这里是getBookListFallBack方法,当getBookList方法跑出异常时将会调用getBookListFallBack方法。注意:回退方法应该与作为hystrix命令调用的方法具有相同的签名。4.创建application.yml:
server: port: 8083spring: application: name: sc-consumer-hystrix-ribbon eureka: client: registerWithEureka: false serviceUrl: defaultZone: http://localhost:8080/eureka/
5.测试
依次启动注册中心sc-eureka、提供者sc-provider、消费者sc-consumer-hystrix-ribbon,并访问http://localhost:8083/getBookList,结果显示如下:
这是提供者正常返回的值,接下来将提供者sc-provider关闭,再次访问http://localhost:8083/getBookList,结果显示如下:
因为将提供者sc-provider关闭后,消费者再访问提供者时会报错,Hystrix捕获异常后会直接调用回退方法也就是getBookListFallBack方法。
在Feign上使用Hystrix
1.在父模块下创建子模块项目sc-consumer-hystrix-feign,pom.xml:
4.0.0 com.cf sc-parent 0.0.1-SNAPSHOT sc-consumer-hystrix-feign org.springframework.cloud spring-cloud-starter-netflix-eureka-client org.springframework.cloud spring-cloud-starter-openfeign org.springframework.cloud spring-cloud-starter-netflix-hystrix
2.创建启动类feign.FeignApplication:
package feign;import org.springframework.boot.SpringApplication;import org.springframework.boot.autoconfigure.SpringBootApplication;import org.springframework.cloud.client.circuitbreaker.EnableCircuitBreaker;import org.springframework.cloud.openfeign.EnableFeignClients;@SpringBootApplication@EnableFeignClients@EnableCircuitBreakerpublic class FeignApplication { public static void main(String[] args) { SpringApplication.run(FeignApplication.class, args); }}
3.创建Feign声明式接口:feign.inter.BookService
package feign.inter;import org.springframework.cloud.openfeign.FeignClient;import org.springframework.web.bind.annotation.PostMapping;import feign.fallback.BookFallBack;@FeignClient(value="sc-provider", fallbackFactory=BookFallBack.class)public interface BookService { @GetMapping("/book/list") public String getBookList();}
@FeignClient注解中的fallbackFactory属性是指定的Feign客户端界面定义回退工厂。
4.创建调用提供者服务的Controller:
package feign.controller;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.web.bind.annotation.GetMapping;import org.springframework.web.bind.annotation.RequestMapping;import org.springframework.web.bind.annotation.RestController;import feign.inter.BookService;@RequestMapping("/feign")@RestControllerpublic class FeignController { @Autowired private BookService bookService; @GetMapping("/getBookList") public String getBookList(){ return bookService.getBookList(); }}
5.创建application.yml:
server: port: 8084spring: application: name: sc-consumer-hystrix-feigneureka: client: registerWithEureka: false serviceUrl: defaultZone: http://localhost:8080/eureka/ feign: hystrix: enabled: true #开启hystrix支持
6.创建回退工厂类:
package feign.fallback;import org.springframework.stereotype.Component;import feign.hystrix.FallbackFactory;import feign.inter.BookService;@Componentpublic class BookFallBack implements FallbackFactory{ @Override public BookService create(Throwable cause) { return new BookService() { @Override public String getBookList() { return "[\"Java入门到放弃\"]"; } }; }}
create方法返回一个回退实例,回退实例为Feign声明式接口BookService的实现类,提供了与BookService相对应的回退方法,BookService接口调用失败时将会调用该实现类中的回退方法。
7.测试:
依次启动注册中心sc-eureka、提供者sc-provider、消费者sc-consumer-hystrix-feign,并访问http://localhost:8084/feign/getBookList,结果显示如下:
这是提供者正常返回的值,接下来将提供者sc-provider关闭,再次访问http://localhost:8084/feign/getBookList,结果显示如下:
8.查看回退原因
修改回退工厂类BookFallBack:
@Componentpublic class BookFallBack implements FallbackFactory{ @Override public BookService create(Throwable cause) { return new BookService() { @Override public String getBookList() { //将回退原因输出到控制台 cause.printStackTrace(System.out); return "[\"Java入门到放弃\"]"; } }; }}
依次启动注册中心sc-eureka、消费者sc-consumer-hystrix-feign,并访问http://localhost:8084/feign/getBookList,控制台输出:
com.netflix.hystrix.exception.HystrixTimeoutException at com.netflix.hystrix.AbstractCommand$HystrixObservableTimeoutOperator$1.run(AbstractCommand.java:1142) at com.netflix.hystrix.strategy.concurrency.HystrixContextRunnable$1.call(HystrixContextRunnable.java:41) at com.netflix.hystrix.strategy.concurrency.HystrixContextRunnable$1.call(HystrixContextRunnable.java:37) at com.netflix.hystrix.strategy.concurrency.HystrixContextRunnable.run(HystrixContextRunnable.java:57) at com.netflix.hystrix.AbstractCommand$HystrixObservableTimeoutOperator$2.tick(AbstractCommand.java:1159) ......