Hystrix是Netflix开源的一个延迟和容错库，用于隔离访问远程系统、服务或者第三方库，防止级联失效，从而提升系统的可用性与容错性。

Hystrix基本使用

添加依赖

<dependency>
   <groupId>org.springframework.cloud</groupId>
   <artifactId>spring-cloud-starter-netflix-hystrix</artifactId>
   <version>2.2.8.RELEASE</version>
</dependency>

为启动类增加@EnableHystrix注解，从而为项目启用断路器支持

@SpringBootApplication
@EnableFeignClients
@EnableHystrix
public class MicroserviceConsumerMovieApplication {

    public static void main(String[] args) {
        SpringApplication.run(MicroserviceConsumerMovieApplication.class, args);
    }

}

修改方法，增加容错能力

  @GetMapping("/user/{id}")
    @HystrixCommand(fallbackMethod = "findByIdFallback",
            commandProperties = {
                    @HystrixProperty(name = "execution.isolation.thread.timeoutInMilliseconds", value = "5000"),
                    @HystrixProperty(name = "metrics.rollingStats.timeInMilliseconds", value = "10000")
            },
            threadPoolProperties = {
                    @HystrixProperty(name = "coreSize", value = "1"),
                    @HystrixProperty(name = "maxQueueSize", value = "10")
            })
    public User findById(@PathVariable Long id) {
        return userFeignClient.findById(id);
    }

    public User findByIdFallback(Long id, Throwable throwable) {
        log.info(throwable.getMessage());
        User user = new User();
        user.setName("默认用户");
        return user;
    }

测试

我们断开此时的服务提供者，访问方法，可以看到进入了容错方法，并获取到了异常信息。

feign集成hystrix

feign:
  circuitbreaker:
    enabled: true

早期版本的Spring Cloud需要配置如下

feign:
  hystrix:
    enabled: true

为feign添加回退

通过fallback添加回退

通过fallback添加回退，不能获取回退原因。

@FeignClient(name = "microservice-provider-user",fallback = UserFeignClientCallback.class)
public interface UserFeignClient {

    /**
     * 使用Feign自带的注解 @RequestLine
     * @param id
     * @return
     */
    @RequestLine("GET /{id}")
    User findById(@Param("id") Long id);

}

@Slf4j
@Component
class UserFeignClientCallback implements UserFeignClient{

    /**
     * 使用Feign自带的注解 @RequestLine
     *
     * @param id
     * @return
     */
    @Override
    public User findById(Long id) {
        User user = new User();
        user.setName("默认用户");
        return user;
    }
}

通过fallbackFactory添加回退

fallbackFactory是fallback的升级版本，能够获取到回退原因。

@FeignClient(name = "microservice-provider-user",fallbackFactory = UserFeignClientCallbackFactory.class)
public interface UserFeignClient {

    /**
     * 使用Feign自带的注解 @RequestLine
     * @param id
     * @return
     */
    @RequestLine("GET /{id}")
    User findById(@Param("id") Long id);

}

@Slf4j
@Component
class UserFeignClientCallbackFactory implements FallbackFactory<UserFeignClient> {


    @Override
    public UserFeignClient create(Throwable cause) {
        return new UserFeignClient() {
            @Override
            public User findById(Long id) {
                log.info(cause.getMessage());
                User user = new User();
                user.setName("默认用户");
                return user;
            }
        };
    }
}

feign项目中Hystrix的监控

首先需要添加依赖

<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-netflix-hystrix</artifactId>
    <version>2.2.8.RELEASE</version>
</dependency>
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-actuator</artifactId>
</dependency>

启动类添加@EnableHystrix

@SpringBootApplication
@EnableFeignClients
@EnableHystrix
public class MicroserviceConsumerMovieApplication {

    public static void main(String[] args) {
        SpringApplication.run(MicroserviceConsumerMovieApplication.class, args);
    }

}

修改配置文件，暴漏地址

management:
  endpoints:
    web:
      exposure:
        include: hystrix.stream

测试

打开地址http://localhost:8081/actuator/hystrix.stream

使用hystrix-dashboard可视化监控项目

我们刚才项目监控时，返回的都是Json数据，通过hystrix-dashboard我们可以实现可视化的监控。

添加hystrix-dashboard依赖

<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-netflix-hystrix-dashboard</artifactId>
    <version>2.2.8.RELEASE</version>
</dependency>

在启动类添加@EnableHystrixDashboard注解

@SpringBootApplication
@EnableFeignClients
@EnableHystrix
@EnableHystrixDashboard
public class MicroserviceConsumerMovieApplication {

    public static void main(String[] args) {
        SpringApplication.run(MicroserviceConsumerMovieApplication.class, args);
    }

}

修改配置文件

配置文件添加

hystrix:
  dashboard:
    proxy-stream-allow-list: "*"

如果不添加，监控会提示Unable to connect to Command Metric Stream.

测试

打开http://localhost:8081/hystrix,监控地址输入http://localhost:8081/actuator/hystrix.stream,title随便输入即可。
点击Monitor Stream，然后访问任意的接口，系统输出界面如下