spring cloud 学习笔记0x4

[hugeterry]

熔断器Hystrix

ribbon+Hystrix

• 使用笔记0x2的eurekaribbon工程，在pom中增加hystrix的起步依赖

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

• 在application启动类中添加@ EnableHystrix,开启Hystrix

@SpringBootApplication
@EnableEurekaClient
@EnableHystrix
public class EurekaribbonApplication {

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

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

• 改造RibbonService，加上@HystrixCommand，创建熔断器

@Service
public class RibbonService {
    @Autowired
    RestTemplate restTemplate;

    @HystrixCommand(fallbackMethod = "errorService")
    public String niceService(String name) {
        return restTemplate.getForObject("http://EUREKACLIENT/nice?name=" + name, String.class);
    }

    public String errorService(String name) {
        return "sorry," + name;
    }
}

注解HystrixCommand指定fallbackMethod熔断方法，熔断方法返回抱歉提示的字符串

• 关闭端口8662,8664的进程，请求http://localhost:8661/b?name=hdusdhu ，此时熔断器发挥作用，会看到
  sorry,hdusdhu

feign+Hystrix

• 使用笔记0x3的eurekafeign工程，在配置文件中开启熔断器
  feign.hystrix.enabled=true

  feign本身含有熔断器，D版本后默认没有打开

• 对InvokeService进行改造在@ FeignClient注解中加入fallback的指定类

@FeignClient(value = "eurekaclient", fallback = InvokeServiceHystric.class)
public interface InvokeService {
    @RequestMapping(value = "/nice", method = RequestMethod.GET)
    String sayService(@RequestParam(value = "name") String name);
}

• InvokeServiceHystric需要实现InvokeService，并注入到ioc中

@Component
public class InvokeServiceHystric implements InvokeService {
    @Override
    public String sayService(String name) {
        return "sorry," + name;
    }
}

• 启动eurekafeign服务，打开http://localhost:8665/feign?name=hugeterry ，会正确显示8662，8664的端口返回报文，将8662，8664进程关闭，此时熔断器响应，看到返回如下报文:
  sorry,hugeterry

命令

• 查看端口进程命令 lsof -i:-P
  P为端口号例如：lsof -i:4200
• 关闭进程命令 kill -9 [pid]