服务启动时，有什么机制能控制先不注入流量，等服务配置加载初始化都完成后，再注入流量吗？

现在主要是在一种动态扩容场景，比如A调用B，现在需要增加一个B服务的实例B1，由于B1启动时，需要拉取很多配置信息，需要耗费一定的时长，若这个时候A来调用B1，则会出现请求调用失败，想看看ServiceComb有没有机制来避免这种问题，比如B1启动完成时，再通知服务中心A可以调用B1了。

No files or tests are named. Start by tracing service startup, configuration loading, and service-center registration for a newly added instance; define how readiness should prevent traffic before initialization completes. Done means a B1 instance is not discoverable or callable until its configuration is loaded and startup is complete.

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