From: Deepak Jain (no email)
Date: Mon May 05 2008 - 00:32:35 EDT
> note that joe's example brings up the interface before starting the name
> server program, and bringing it down if the name server program exits.
> this presumes that the name server will start very quickly, and that while
> running, it is healthy. since i've seen name server programs be unhealthy
> while running, and/or take a long time to start, i'm now considering an
> outboard shell script that runs some kind of DNS query and decides, based
> on the result, whether to bring the dedicated loopback interface up or down.
All deference to this model, we've all seen these kinds of problems with
name servers. We *can* be certain that bringing a loopback interface up
or down takes almost no time (with the implied effect to a speaker like
Quagga). There is *no* reason with a sufficiently deep name server depth
(depends on your load) that your monitoring script should *need* to
hurry to test this condition. Every 5-10 or even 15 minutes to see if
its eligible to bring up, more frequently to see if its eligible to take
down. This also reduces oscillation.
This means, bring up/kill off your name server in one cronjob
(automatically taking the interface down at the end or after a kill),
and monitor/talk to the interface in another (up function and sometimes
the down).
You'll be much happier.
Deepak Jain
AiNET
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