spring cloud hystrix在普通应用和feign上使用

hystrix普通用法

• 引入包

<dependency>
    <groupId>org.springframework.cloudgroupId>
    <artifactId>spring-cloud-starter-hystrixartifactId>
dependency>

• 在main类中添加注解@EnableCircuitBreaker

@SpringBootApplication
@EnableEurekaClient
@EnableCircuitBreaker
public class MicroserviceSimpleConsumerApplication {

    @Bean
    @LoadBalanced
    public RestTemplate restTemplate() {
        return new RestTemplate();
    }

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

• 在接口处实现fallback方法使用@HystrixCommand注解，指明方法名

 @GetMapping("/consumer/{id}")
    @HystrixCommand(fallbackMethod = "findByIdFallback", commandProperties = @HystrixProperty(name = "execution.isolation.strategy", value = "SEMAPHORE"))
    public User findById(@PathVariable("id") Long id) {
        return this.restTemplate.getForObject("http://SIMPLE-PROVIDER/provider/" + id, User.class);
    }

    public User findByIdFallback(Long id) {
        User u = new User();
        u.setId(-1L);
        return u;
    }

hystrix在feign中应用

注意的是：fegin中默认hystrix功能是关闭的，具体见https://github.com/spring-cloud/spring-cloud-netflix/issues/1277

• 首先开启feign中的hystrix功能

  feign:
  hystrix:
  enabled: true

• 使用 @FeignClient 注解属性进行设置fallback

@FeignClient(name = "SIMPLE-PROVIDER", fallback = HystrixFallBackClient.class)
public interface UserFeignClient {

    @GetMapping("/provider/{id}")
    public User findUserById(@PathVariable("id") Long id);
}

• 写fallback的类

package com.example.demo.client;

import org.springframework.stereotype.Component;

import com.example.demo.entity.User;

@Component
public class HystrixFallBackClient implements UserFeignClient {

    @Override
    public User findUserById(Long id) {
        User user = new User();
        user.setId(0L);
        return user;
    }
}

另外一种写fallback方法

• 利用fallbackFactory进行编写（原理和直接写fallback类似，但factory可以提供异常信息）

@FeignClient(name = "SIMPLE-PROVIDER", configuration = UserFeignClientConfig.class, /**fallback = UserFeignClientFallback.class,**/ fallbackFactory = UserClientfallbackFactory.class)
public interface UserFeignClient {

    @GetMapping("/provider/{id}")
    @HystrixCommand(fallbackMethod = "findUserByIdFallback")
    public User findUserById(@PathVariable("id") Long id);
}

• 编写factory类实现client接口

package com.example.demo.client;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Component;

import com.example.demo.entity.User;

import feign.hystrix.FallbackFactory;

@Component
public class UserClientfallbackFactory implements FallbackFactory<UserFeignClient> {

    Logger log = LoggerFactory.getLogger(UserClientfallbackFactory.class);

    @Override
    public UserFeignClient create(Throwable cause) {
        return new UserFeignClient() {

            @Override
            public User findUserById(Long id) {
                log.info("fall back cause :{}", cause.getMessage());
                User u = new User();
                u.setId(-2L);
                u.setName("fallbackFactory");
                return u;
            }

        };

    }

}

注意的是：@FeignClient 中的fallback和fallbackFactory只能同时配一个

hystrix用法总结

– 使用hystrix自生的注解
– 使用feign注解中的设置