SpringCloud Feign Hystrix后備

Hystrix支持回退的概念：當它們的電路斷開或出現(xiàn)錯誤時執(zhí)行的默認代碼路徑。要為給定的@FeignClient啟用回退，請將fallback屬性設置為實現(xiàn)回退的類名稱。您還需要將實現(xiàn)聲明為Spring bean。

@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");
    }
}

如果需要訪問引起后備觸發(fā)器的原因，則可以使用@FeignClient中的fallbackFactory屬性。

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

@Component
static class HystrixClientFallbackFactory implements FallbackFactory<HystrixClient> {
	@Override
	public HystrixClient create(Throwable cause) {
		return new HystrixClient() {
			@Override
			public Hello iFailSometimes() {
				return new Hello("fallback; reason was: " + cause.getMessage());
			}
		};
	}
}

Feign中的后備實現(xiàn)以及Hystrix后備如何工作存在局限性。返回com.netflix.hystrix.HystrixCommand和rx.Observable的方法當前不支持后備。