On Apr 20, 2016, at 3:40 PM, user-87556346d4af@xymon.invalid wrote:
Date: Wed, 20 Apr 2016 15:40:14 -0700
From: "J.C. Cleaver" <user-87556346d4af@xymon.invalid>
To: "Xymon Mailing List" <xymon at xymon.com>
Subject: Re: [Xymon] Xymon disruption every night!
Message-ID:
<user-cb72d07412d6@xymon.invalid>
Content-Type: text/plain;charset=iso-8859-1
On Wed, April 20, 2016 12:55 pm, Greg Earle wrote:
On Feb 17, 2016, at 12:50 AM,"J.C. Cleaver" <user-87556346d4af@xymon.invalid>
wrote:
- Why I have a "DNS error" here ? I set up the IP yesterday to this
host
to solve the issue. The "conn" error disappeared since yesterday
evening
but the http error still remains.
All signs do point to an issue with DNS resolution here.
Was this a custom compile or are you using a package? If custom, what
version of c-ares is on your system? That's the underlying resolution
library that xymonnet is using by default to handle DNS lookups. The
fact that the 'conn' test remained good after you added the local hosts
entry matches that, since HTTP tests are performed using their own
secondary DNS lookup (to deal with vhosts, etc.) unless the IP is
specified there as well.
J.C.,
I just stumbled across this thread from 2 months ago. We're having DNS
glitches at my work and it's causing a flood of <hostname>:http
"DNS error" alerts in Xymon, which is becoming a real problem.
But here's what I don't understand. All of our HTTP-tested hosts are
in the "hosts.cfg" file with their short names (instead of FQHNs). So I
couldn't understand why DNS was involved since the IP addresses and names
were right there in "hosts.cfg" for Xymon to use.
Your response - specifically "unless the IP is specified there as well" -
implies that there might be another location where I could load the
names and addresses of our HTTP-tested hosts, to avoid this problem.
(Yes, I know - hosts and IP addresses can change. But I'm in control of
that so I can deal.)
If this is the case, where is that other location where I can specify the
short names/IP addresses for the HTTP tests?
Yep: https://xymon.com/help/manpages/man5/hosts.cfg.5.html#lbAR
192.168.0.10 mywebserver # http://www.sample.com=192.168.0.10/
For HTTP tests, an IP override is put in for each URL you're using. This
will prevent a DNS lookup at http-test time for this URL, and when
combined with combined with testip (for any other TCP checks here) and
noconn (for ping->fping resolution), it should prevent any DNS lookups
from being done for the string "mywebserver".
Unless there's been a regression, that should be sufficient. It's
definitely worked at scale for mass testing of "hosts" that are not being
referred to by a valid DNS name and simply listen on a distinct port.