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Re: DNS & multiple names and copy statements

Subject: Re: DNS & multiple names and copy statements
From: Andrew Stribblehill
Date: Fri, 23 Dec 2005 18:58:50 +0000
Newsgroups: gnu.cfengine.help
Quoting Martin, Jason H <jason.h.martin@xxxxxxxxxxxx> (2005-12-06 00:05:30 GMT):
> Has there been any thought into having CFE do failover based on a given
> name returning multiple IP addresses? Lets  say www.yahoo.com was
> hosting my CFE server:
> 
> # host www.yahoo.com
> www.yahoo.com is an alias for www.yahoo.akadns.net.
> www.yahoo.akadns.net has address 68.142.197.85
> www.yahoo.akadns.net has address 68.142.197.64
> www.yahoo.akadns.net has address 68.142.197.65
> www.yahoo.akadns.net has address 68.142.197.67
> www.yahoo.akadns.net has address 68.142.197.68
> www.yahoo.akadns.net has address 68.142.197.76
> www.yahoo.akadns.net has address 68.142.197.80
> www.yahoo.akadns.net has address 68.142.197.83
> 
> Cfagent could iterate over the whole list trying to perform a copy,
> instead of requiring the user to add a 'failover=' line (which is
> therefore limited to just 2 potential sources). One could even expand on
> that to have it randomly choose from the list or do some sort of check
> (ie ping) to try them in some order. This would be very handy when one
> has CFE clients on opposite ends of a 3-way WAN pipe with a CFE server
> on each end. Clients would pick the best available server and fail over
> to the next best on down until they get one that worked.

I agree, something would be useful. I've been looking at DNS SRV
records of late, and they cope with this sort of issue. Think of them
as a cross between CNAMEs, DNS round-robin and MX records. However,
it would require bespoke DNS queries to take advantage of SRV.

http://www.dur.ac.uk/a.d.stribblehill/dns+srv.html describes the
system.

-- 
SHANNON SOUTH ROCKALL
SOUTHWEST BACKING SOUTH OR SOUTHEAST 4 OR 5. OCCASIONAL RAIN AT
FIRST. MODERATE OR GOOD

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