[nsd-users] NSD4 goes unresponsive with lots of TCP connection!
kabindra at geeks.net.np
Tue Apr 5 16:28:04 UTC 2016
We are seeing some large number of TCP connections to our DNS servers (in thousands) and NSD goes unresponsive after certain time and doesn't recover, it stops responding to UDP as well. We tried increasing the number of tcp-counts but it doesn't help.
I noticed the TCP backlog is hardcoded to 256 in NSD config, so even with customised TCP backlogs on the system its still being throttled at around 256. Is there anyway we can change this value without recompiling the NSD.
[kabindra at 05 nsd-4.1.8]$ grep BACKLOG *
configure:#define TCP_BACKLOG 256
configure.ac:AC_DEFINE_UNQUOTED([TCP_BACKLOG], , [Define to the backlog to be used with listen.])
We are using NSD4.1.8.
( From one of the servers that went unresponsive, we have seen that TCP number closing to 10k. )
Total: 5591 (kernel 5640)
TCP: 5067 (estab 4968, closed 4, orphaned 0, synrecv 0, timewait 3/0), ports 28
Transport Total IP IPv6
* 5640 - -
RAW 0 0 0
UDP 122 63 59
TCP 5063 5017 46
INET 5185 5080 105
FRAG 0 0 0
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