概览
Ribbon | Feign | Zuul |
---|---|---|
使用的是@HystrixCommand注解,其实就是一个api | 针对一个类,使用的是fallback属性 | 针对一个或多个微服务 |
Ribbon的Fallback机制
==使用的是@HystrixCommand注解,其实就是一个api ;==
如下:
@HystrixCommand(fallbackMethod = "defaultStores")
这个注解是通用的,不一定是Ribbon才用;
如何使用:
@Component
public class StoreIntegration {
@HystrixCommand(fallbackMethod = "defaultStores")
public Object getStores(Map<String, Object> parameters) {
//do stuff that might fail
}
public Object defaultStores(Map<String, Object> parameters) {
return /* something useful */;
}
}
如果要让某些线程本地上下文传播到@HystrixCommand,则默认声明不起作用,因为它在线程池中执行该命令(可能造成超时)。 通过配置或直接在注释中切换Hystrix以使用与调用者相同的线程,方法是要求它使用不同的“隔离策略”。
以下示例演示如何在注释中设置线程:
@HystrixCommand(fallbackMethod = "stubMyService",
commandProperties = {
@HystrixProperty(name="execution.isolation.strategy", value="SEMAPHORE")
}
)
...
@HystrixCommand由名为“javanica”的Netflix contrib库提供。 Spring Cloud在连接到Hystrix断路器的代理中自动包装带有该注释的Spring bean。 断路器计算何时打开和关闭电路以及在发生故障时应采取的措施。
See here for more details. See the Hystrix wiki for details on the properties available.
Feign的Fallback机制
==针对一个类,使用的是fallback属性==
如下:
-
第一种fallback形式:
@FeignClient(name = "hello", fallback = HystrixClientFallback.class)
- 代码示例:
@FeignClient(name = "microservice-provider-user", fallback = HystrixClientFallback.class) public interface UserFeignClient { @RequestMapping(method = RequestMethod.GET, value = "/user/{id}", consumes = "application/json") public User findById(@PathVariable("id") Long id); } static class HystrixClientFallback implements UserFeignClient { @Override public User findById(Long id) { User user = new User(); user.setId(1L); return user; } }
-
第二种:fallbackFactory形式
@FeignClient(name = "microservice-provider-user", /*fallback = HystrixClientFallback.class, */ fallbackFactory = HystrixClientFallbackFactory.class)
- 代码示例:
@FeignClient(name = "microservice-provider-user", /*fallback = HystrixClientFallback.class, */ fallbackFactory = HystrixClientFallbackFactory.class) public interface UserFeignClient { @RequestMapping(method = RequestMethod.GET, value = "/user/{id}", consumes = "application/json") public User findById(@PathVariable("id") Long id); } @Component static class HystrixClientFallbackFactory implements FallbackFactory<UserFeignClient> { private static Logger LOGGER = LoggerFactory.getLogger(HystrixClientFallbackFactory.class); @Override public UserFeignClient create(Throwable cause) { //打印日志 HystrixClientFallbackFactory.LOGGER.info("fallback; reason was: " + cause.getMessage()); return new UserFeignClient() { @Override public User findById(Long id) { User user = new User(); user.setId(-1L); user.setUsername("我是HystrixClientFallbackFactory"); return user; } }; } }
Zuul的Fallback机制
==针对一个微服务==