node1.npulse.net
Did you see one of our IP like 91.82.18.20 or 2001:1aa3:4:0:4e50:554c:5345:2 in your log file?
Nothing to worry about it's just our monitoring system, seems like someone really care of your services, totally harmless.
Our services may ping your services to detect it's state, this is performed maximum once per minute this is part of the normal usage of internet.
Interested? for more details check out our website: nPulse.net