Newly added/Removed ServiceInstance should be passed to ServiceCacheListener#cacheChanged method

Hey fellows,

We're using service discovery extension to refactor our raw zookeeper based service monitor.

Every time a service instance exits or joins, the monitor must be notified and push a notification to us, the only thing I found in service discovery package meets the requirement is ServiceCacheListener interface, but when the interface is fired, there's no way we could know which service has changed.

Please help !

Thank in advance.