Strange thing : User dcui@127.0.0.1 logged in and out messages flooding in event list

In ESXi's hot web page's event list, nearly every minutes, there are messages saying "User dcui@127.0.0.1 logged in as" and immediately "User dcui@127.0.0.1 logged out". Even if I reboot the host, the messages continues. What does the message come from? 127.0.0.1 seems it comes from the host itself, why? What it is doing?

ESXi: 6.0.0 Update 3 (Build 5050593)

And, I inspected /var/log/hostd.log, it has more details:

Want to know the reason. And what is sub=Vimsvc.ha-eventmgr? is Vimsvc.ha-eventmgr related to High Availablity?

Thanks a lot!