A program which can monitor HTTP service and change DNS recor d on fail?

[Sam Pointer]

Here we do something crude, but it works. We have 2 leased lines with 2
different IP ranges. All of our webservers are multihomed. We autogenerate
our DNS info from an internal database.

Usually our DNS info presents both IP addresses for any given webserver.
This does some crude load-balancing (we're not high volume). An in-house
perl script does HTTP GETs and PINGs to major sights. Using a very simple
algorithm it decides when one of our lines has gone bad. I get an SMS
message.

Then all I do is log on, verify the situation and run a script which issues
a reload to BIND giving it a configuration containly only one of the IP
ranges (whichever is the `good` line).

All of our caching values are set to 0 (like I said, low volume) so the
change is more of less instant. Mostly people are unaware, execpt for
dropped ssh sessions and the like.

Not great or fancy, but it works for us and is good enough as an ad-hoc
"resilience" solution. It is obviously not very scalable and relies heavily
on the in-house nameservers.

Just a thought.

-----Original Message-----
From: Barry Margolin [mailto:barmar at genuity.net]
Sent: 04 April 2002 16:42
To: comp-protocols-dns-bind at isc.org
Subject: Re: A program which can monitor HTTP service and change DNS
record on fail?


In article <a8g7q9$1hf at pub3.rc.vix.com>,
Steven E. Ames <sames at officescape.com> wrote:
>
>From a data center perspective couldn't you just use BGP to broadcast
>the same subnet from two different locations? When the route to one
>fails traffic won't even try going to it. No DNS witchery involved. You
>want IP failover right? So it really should be handled at the IP layer.

That will work if you can get a full class C or larger block, or if all
your data centers are connected to the same ISP.

-- 
Barry Margolin, barmar at genuity.net
Genuity, Woburn, MA
*** DON'T SEND TECHNICAL QUESTIONS DIRECTLY TO ME, post them to newsgroups.
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