CollectSinkOperatorCoordinator checkpointed its address field to state and restored back. That field is listener address of CollectSinkFunction. After resetToCheckpoint (eg. global failover}}, address is meaningless. If client request comes before CollectSinkAddressEvent, it will use that meaningless address for connection. In best situation, error happens, and nothing hurts. In bad situation, no one knows where the restored address points to now.