从零开始学spring cloud(十) -------- hystrix简单代码示例

一、官网文档阅读

较低级别的服务中的服务故障可能导致级联故障一直到用户。 当对特定服务的调用超过circuitBreaker.requestVolumeThreshold（默认值：20个请求）且失败百分比大于circuit.rolllingStats.timeInMilliseconds定义的滚动窗口中的circuitBreaker.errorThresholdPercentage（默认值：> 50％）时（默认值：10秒） ，电路打开，没有拨打电话。 在出现错误和开路的情况下，开发人员可以提供回退。

二、示例

添加hystrix依赖

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

修改movie服务的controller

 package com.zwjk.cloud.controller;

 import com.netflix.hystrix.contrib.javanica.annotation.HystrixCommand;
 import com.zwjk.cloud.entity.User;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.beans.factory.annotation.Value;
 import org.springframework.cloud.client.ServiceInstance;
 import org.springframework.cloud.client.loadbalancer.LoadBalancerClient;
 import org.springframework.web.bind.annotation.GetMapping;
 import org.springframework.web.bind.annotation.PathVariable;
 import org.springframework.web.bind.annotation.RestController;
 import org.springframework.web.client.RestTemplate;

 /**
  * @author : Jixiaohu
  * @Date : 2019-04-11.
  * @Time : 9:38.
  * @Description :
  */
 @RestController
 public class MovieController {

     @Autowired
     private RestTemplate restTemplate;

     @Value("${user.userServicePath}")
     private String userServicePath;

     @GetMapping("/movie/{id}")
     @HystrixCommand(fallbackMethod = "findByIdFallback")
     public User findById(@PathVariable Long id) {
         return this.restTemplate.getForObject(this.userServicePath + id, User.class);
     }

     public User findByIdFallback(Long id) {
         User user = new User();
         user.setId(0L);
         user.setName("失败");
         return user;
     }
 }

这边需要注意的是，fallbackMethod方法的返回值和入参，必须和原方法一致，下面进行测试：

可以看到，这里返回了正常的结果，下面停掉user服务

可以看到，这里返回的结果，就是fallbackMethod里面返回的内容，hystrix就起了作用。

下面，继续看一下

Feign Hystrix Support

参考官网使用示例：

 @FeignClient(name = "hello", fallback = HystrixClientFallback.class)
 protected interface HystrixClient {
     @RequestMapping(method = RequestMethod.GET, value = "/hello")
     Hello iFailSometimes();
 }

 static class HystrixClientFallback implements HystrixClient {
     @Override
     public Hello iFailSometimes() {
         return new Hello("fallback");
     }
 }

在配置文件中，增加开启feign使用断路器

feign:
  hystrix:
    enabled: true

按照示例，我们在movie服务中，新增UserFeignClientFallback类

 package com.zwjk.cloud.fegin;

 import com.zwjk.cloud.entity.User;
 import org.springframework.stereotype.Component;

 /**
  * @author : Jixiaohu
  * @Date : 2019-04-17.
  * @Time : 18:20.
  * @Description :
  */
 @Component
 public class UserFeignClientFallback implements UserFeignClient {
     @Override
     public User findById(Long id) {
         User user = new User();
         user.setId(0L);
         return user;
     }
 }

在fegin上增加相应的注解：

 package com.zwjk.cloud.fegin;

 import com.zwjk.cloud.entity.User;
 import org.springframework.cloud.openfeign.FeignClient;
 import org.springframework.web.bind.annotation.GetMapping;
 import org.springframework.web.bind.annotation.PathVariable;
 import org.springframework.web.bind.annotation.PostMapping;
 import org.springframework.web.bind.annotation.RequestBody;

 /**
  * @author : Jixiaohu
  * @Date : 2019-04-12.
  * @Time : 16:50.
  * @Description :
  */
 @FeignClient(name = "microservice-provider-user", fallback = UserFeignClientFallback.class)
 public interface UserFeignClient {
     //@PathVariable得设置value
     @GetMapping("/simple/{id}")
     User findById(@PathVariable("id") Long id); //@PathVariable得设置value
 }

启动项目，进行测试，

同样的，停掉user服务，再次访问这个地址：

就可以实现熔断服务

当一个项目中，有个feign时，如何禁用一些feign的hystrix？

查看一下官网文档

通过配置加上feignBuilder,就可以禁用指定fegin的hystrix

查看一下代码实现：

 package com.zwjk.cloud.controller;

 import com.zwjk.cloud.entity.User;
 import com.zwjk.cloud.fegin.UserFeignClient2;
 import com.zwjk.cloud.fegin.UserFeignClient;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.web.bind.annotation.GetMapping;
 import org.springframework.web.bind.annotation.PathVariable;
 import org.springframework.web.bind.annotation.RestController;

 /**
  * @author : Jixiaohu
  * @Date : 2019-04-11.
  * @Time : 9:38.
  * @Description :
  */
 @RestController
 public class MovieController {

     @Autowired
     private UserFeignClient userFeignClient;

     @Autowired
     private UserFeignClient2 userFeignClient2;

     @GetMapping("/movie/{id}")
     public User findById(@PathVariable Long id) {
         return this.userFeignClient.findById(id);
     }

     @GetMapping("/{serviceName}")
     public String findServiceInfoFromEurekaByServiceName(@PathVariable String serviceName) {
         return this.userFeignClient2.findServiceInfoFromEurekaByServiceName(serviceName);
     }

 }

两个fegin：

 package com.zwjk.cloud.fegin;

 import com.zwjk.cloud.entity.User;
 import com.zwjk.config.UserConfiguration;
 import feign.Param;
 import feign.RequestLine;
 import org.springframework.cloud.openfeign.FeignClient;

 /**
  * @author : Jixiaohu
  * @Date : 2019-04-12.
  * @Time : 16:50.
  * @Description :
  */
 @FeignClient(name = "microservice-provider-user", configuration = UserConfiguration.class, fallback =
     UserFeignClientFallback.class)
 public interface UserFeignClient {
     //@PathVariable得设置value
     @RequestLine("GET /simple/{id}")
     User findById(@Param("id") Long id); //@PathVariable得设置value

 }

 package com.zwjk.cloud.fegin;

 import com.zwjk.config.UserConfiguration2;
 import org.springframework.cloud.openfeign.FeignClient;
 import org.springframework.web.bind.annotation.PathVariable;
 import org.springframework.web.bind.annotation.RequestMapping;

 /**
  * @author : Jixiaohu
  * @Date : 2019-04-13.
  * @Time : 11:23.
  * @Description :
  */
 @FeignClient(name = "xxxx", url = "http://192.168.1.114:8761/", configuration = UserConfiguration2.class)
 public interface UserFeignClient2 {
     @RequestMapping(value = "/eureka/apps/{serviceName}")
     public String findServiceInfoFromEurekaByServiceName(@PathVariable("serviceName") String serviceName);
 }

两个fallback

 package com.zwjk.cloud.fegin;

 import org.springframework.stereotype.Component;

 /**
  * @author : Jixiaohu
  * @Date : 2019-04-17.
  * @Time : 18:20.
  * @Description :
  */
 @Component
 public class UserFeignClient2Fallback implements UserFeignClient2 {

     @Override
     public String findServiceInfoFromEurekaByServiceName(String serviceName) {
         return "hahahha";
     }
 }

 package com.zwjk.cloud.fegin;

 import com.zwjk.cloud.entity.User;
 import org.springframework.stereotype.Component;

 /**
  * @author : Jixiaohu
  * @Date : 2019-04-17.
  * @Time : 18:20.
  * @Description :
  */
 @Component
 public class UserFeignClientFallback implements UserFeignClient {
     @Override
     public User findById(Long id) {
         User user = new User();
         user.setId(0L);
         return user;
     }
 }

看一下两个配置文件

 package com.zwjk.config;

 import feign.Contract;
 import feign.Logger;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;

 /**
  * @author : Jixiaohu
  * @Date : 2019-04-13.
  * @Time : 10:20.
  * @Description :
  */
 @Configuration
 public class UserConfiguration {

     @Bean
     public Contract feignContract() {
         return new feign.Contract.Default();
     }

     @Bean
     Logger.Level feignLoggerLevel() {
         return Logger.Level.FULL;
     }
 }

 package com.zwjk.config;

 import feign.Feign;
 import feign.auth.BasicAuthRequestInterceptor;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.context.annotation.Scope;

 /**
  * @author : Jixiaohu
  * @Date : 2019-04-13.
  * @Time : 11:25.
  * @Description :
  */
 @Configuration
 public class UserConfiguration2 {
     @Bean
     public BasicAuthRequestInterceptor basicAuthRequestInterceptor() {
         return new BasicAuthRequestInterceptor("user", "password123");
     }

     @Configuration
     public class FooConfiguration {
         @Bean
         @Scope("prototype")
         public Feign.Builder feignBuilder() {
             return Feign.builder();
         }
     }
 }

启动服务，进行测试

下面，我们停掉eureka，和user服务，在一次查看返回结果

启用hystrix的返回结果如下：

没有启用hystrix的返回结果，提示500错误

从中，可以看出，hytrix的熔断，可以有很细的粒度。

如果想要查看fallback回退的原因，可以使用可以使用@FeignClient中的fallbackFactory属性。

看一下如何实现？

参考一下官网文档：

先写一个hystrixFactory：

 package com.zwjk.cloud.fegin;

 import com.zwjk.cloud.entity.User;
 import feign.hystrix.FallbackFactory;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import org.springframework.stereotype.Component;

 /**
  * @author : Jixiaohu
  * @Date : 2019-04-17.
  * @Time : 19:37.
  * @Description :
  */
 @Component
 public class UserFeginClientFactory implements FallbackFactory<UserFeignClient> {

     private static final Logger Log = LoggerFactory.getLogger(UserFeginClientFactory.class);

     @Override
     public UserFeignClient create(Throwable cause) {
         UserFeginClientFactory.Log.info("fallback:reason was : {}", cause.getMessage());
         return id -> {
             User user = new User();
             user.setId(-1L);
             user.setName("haha");
             return user;
         };
     }
 }

修改一下原feignClient

 package com.zwjk.cloud.fegin;

 import com.zwjk.cloud.entity.User;
 import org.springframework.cloud.openfeign.FeignClient;
 import org.springframework.web.bind.annotation.GetMapping;
 import org.springframework.web.bind.annotation.PathVariable;
 import org.springframework.web.bind.annotation.PostMapping;
 import org.springframework.web.bind.annotation.RequestBody;

 /**
  * @author : Jixiaohu
  * @Date : 2019-04-12.
  * @Time : 16:50.
  * @Description :
  */
 @FeignClient(name = "microservice-provider-user", fallbackFactory =
     UserFeginClientFactory.class)
 public interface UserFeignClient {
     //@PathVariable得设置value
     @GetMapping("/simple/{id}")
     User findById(@PathVariable("id") Long id); //@PathVariable得设置value
 }

启动user服务，movie服务，先正常访问：

然后关闭user服务，会发现控制台开始打印日志：

这是为什么呢？因为此时，断路器并没有打开，实际的原因是TimeoutException

当断路器打开时，就会答应异常的信息。