[ILUG] DNS based failover for ftp servers?

[Conor Daly]

Hi all,

This is an area where I basically have no clue.  I have an RHEL box that
runs an ftp server to receive incoming files.  I don't necessarily have
control of the upstream suppliers so I need to have something there at all
times to catch incoming files.

A recent failure hung the machine to the point where an ftp connection
would hang waiting for a response.  The machine would respond to pings.  I
took the machine down for repairs and booted another to receive the
incoming ftp files.  I just gave it the primary machine's ip address.

In the course of considering failover possibilities, I note that something
that manages to detect the hung machine would not be able to take over the
task since the hung machine's ip address would be still in use.

So, is there any equivalent in DNS of MX records' priority numbers for
other server types?  Assuming the primary machine is ftp1.example.com and
the backup machine is ftp2.example.com, I would like ftp.example.com to
resolve to ftp1.example.com and only to resolve to ftp2.example.com if
ftp1... is unavailable.  Is this possible to do within a standard DNS
setup?  Even if the DNS is an MS machine?

Alternatively, is there some way by using a short TTL and some kind of
scripting on the DNS to update ftp.example.com's ip?  I would envisage
that ftp2.example.com would run some kind of heartbeat monitor against
ftp1.example.com and would, on heartbeat failure, call the DNS and claim
the ftp.example.com domain.

Any other thoughts come to mind?  Apart from the notion of requesting
upstream suppliers to attempt to send to ftp1... and, if that fails, to send
to ftp2...

Regards,

Conor

-- 
Conor Daly <conor.daly at cod.homelinux.org>
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