On Thu, 20 Jun 2013, Russell Jones wrote:
> For example, I am trying to create a dependency for the local DNS tests
> on my monitoring server for not only all services on all hosts, but also
> the host checks themselves. It seems like if local DNS resolution on the
> monitoring server failed, I will still get host check alerts.
I hate to be a pedant here, but one of the characteristics of a
monitoring/alerting system is that it needs to retain its sanity in
a sometimes-insane world. Sometimes that means that one can't trust
that DNS works which is why it's actually best to hard-code the IP
addresses for servers under monitoring (and is probably the *only*
case where hard-coding IP addresses is a good thing).
As an alternative to hard-coding IP addresses, one could
periodically scrape the DNS and construct an /etc/hosts file
from that which would allow the use of symbolic names and still
preserve sanity if the DNS quit. Other hints I've heard is to
put a slave DNS server on the monitoring host, but what does one
do if^W when *that* goes wonky?
The point is that when the world around you is insane, the
monitoring system must remain a touchstone of sanity and point
the troubleshooters in the right direction with an absolute
minimum of misinformation or meaningless information. That's
why this admin hard-codes his IP addresses and periodically
does a verification run against the DNS to keep sanity (even
though if the IP address changes the monitoring system will
immediately lose contact with the monitored object).
> Thoughts?
I have lots. Some are printable and some are not.
Cheers!
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| Carl Richard Friend (UNIX Sysadmin) | West Boylston |
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