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net-snmp-lvs module fails under high load

I'm using the net-snmp-lvs module to interface LVS statistics to SNMP so I can graph them (I'm using OpenNMS).

I have a virtual HTTP service that is balanced across eight real servers. In testing, everything seemed to work just fine and I got some nice graphs that show the Connection Rate, Packet Rate, and Byte Rate for the virtual service and each of the real servers.

This morning, we attempted a cutover, ie. we re-directed real traffic to the new service. Sadly, our perimeter firewall hit > 90% CPU so we had to revert. But, in the time that we were live, I noticed that the Connection Rate statistics were missing for both the virtual service and the real servers for the period in which the service was under high load:


Notice the gap in the Connection Rate graph when the Packet & Byte rate graphs show high values.

I am currently investigating the cause of this issue.

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