I have a basic health check script on my recursive servers:

#!/bin/sh

digarg="+time=1 +tries=1 +short cam.ac.uk in loc"
digout='52 12 19.000 N 0 7 5.000 E 18.00m 10000m 100m 100m'

for host in 127.0.0.1 ::1
do
	for proto in +ignore +tcp
	do
		case $(dig @$host $proto $digarg) in
		($digout) : ok ;;
		(*) exit 1 ;;
		esac
	done
done
exit 0

I am running a load test using adns-masterfile as described at
http://fanf.livejournal.com/141030.html

This load test involves one client using one UDP socket and one TCP
socket. The client is running on a different machine connecting over a
LAN.

The server is running Linux 3.13.0-77-generic #121-Ubuntu
BIND 9.10.3-P4+0-large <id:03b54c5> built by make with '--enable-threads' '--enable-getifaddrs' '--with-ecdsa=yes' '--with-geoip=no' '--with-gost=no' '--with-gssapi=no' '--with-idn=no' '--with-iconv=no' '--with-libjson=yes' '--with-libxml2=yes' '--with-openssl=yes' '--with-pkcs11=no' '--with-python=yes' '--with-readline=yes' '--with-tuning=large' '--prefix=/home/named/BIND/9.10.3-P4+0' '--mandir=/home/named/BIND/9.10.3-P4+0/man' '--localstatedir=/home/named/var' '--sysconfdir=/home/named/etc'

The server accumulates a lot of completed TCP connections in TIME_WAIT.
When `netstat -an | grep -c TIME_WAIT` gets over 28,000 then the health
check script starts to fail, because `dig` cannot open a TCP connection -
it fails with

	dig: isc_socket_bind: address in use

I think this means that `dig` needs to use ISC_SOCKET_REUSEADDRESS and I
suspect that `named` might need some attention in this area as well.

Tony.
-- 
f.anthony.n.finch  <dot@dotat.at>  http://dotat.at/
Viking, North Utsire: Southerly 5 to 7. Moderate or rough. Mainly fair. Good,
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