On 27/3/2014 4:32 μμ, James Day wrote:
noa.gr relay:noa.gr.local
I have then configured A records for the multiple relay destinations, queries
are then balanced in a DNS round robin fashion.
Yes, I undertand. However, we don't want balancing (our traffic is low -
but we want failover).
In my case, this scenario could be implemented by using a very low TTL
for vmail.noa.gr and then use a script to monitor target and, in case it
does not respond, then update the A record to point to another IP address.
This assumes that Postfix observes the TTL for DNS lookups (on names
used in transport maps).
However, in my case I would not go for this solution because we want
vmail and vmail1 to have different host names (they include Dovecot IMAP
servers replicated using dsync). They cannot behave to others as being
the same host.
One thing that could be done would be to monitor vmail.noa.gr on the
gateway servers and if it does not respond, then use a script to update
transport maps and reload postfix. It does not sound very elegant to me...
(Nor can we employ multiple IP addresses per server; it is a VPS service
offering a single IP address per VM.)
Nick
