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Multiple TCP connections for logging

Question asked by Kaspars Zibarts on May 30, 2018
Latest reply on May 31, 2018 by Vladimir Yakovlev

We have a small problem Houston.

One of our gateways is located in the kingdom far far away with over 200ms latency to the log server. Lately we noticed that part of the logs started to be saved locally on the gateway.

Investigation proved that we have reached the "limit" of a single TCP pipe (latency plus window size) that's around 1.5Mbps. Other evidence includes the fact that 2GB log file on log server never fills faster than 1.5hrs (note though that includes 2 VS logs so technically rate there is 2x1.5=3Mbps) and TCP send queue is noticeable on the gateway.

Solutions could be:

  • keep disabling logging for highly used rules - not ideal as we already have cut a lot of fat
  • bring log server closer to gateway - can't really as we have MLM that serves many other kingdoms far away
  • increase TCP window - not ideal to go any higher as re-transmission overhead would grow a lot
  • transfer locally saved files with a script - but that potentially would introduce noticeable latency in log delivery
  • add the second TCP connection for log transfer because that would double transfer rate capacity

Does anyone know if it's really possible - to have multiple TCP connections for log transfer. I did some digging in UC but did not find anything. I'm interested in VSX "version"

Or does anyone know if we can "split" MLM or have two MLMs?

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