def _OnServersChanged(self, endpoint, channel_factory, added):
    if added:
      self._AddSink(endpoint, channel_factory)
    else:
      self._RemoveSink(endpoint)
Invoked by the LoadBalancer when an endpoint joins or leaves the
dataset/ETHPy150Open steveniemitz/scales/scales/loadbalancer/heap.py/HeapBalancerSink._OnServersChanged