[Freeipa-users] routing requests to local servers - DNS SRV + view?

[Petr Spacek]

On 04/13/2012 10:28 PM, Jakub Hrozek wrote:
> On Fri, Apr 13, 2012 at 01:04:55PM -0700, Brian Cook wrote:
>>     Ideally I would rely on a -group- of servers, and then rely on DNS if it
>>     is down.  I don't want to hammer one server.  We're talking about 500-1000
>>     servers running virtual machines, so potentially a lot of traffic.  Got
>>     any suggestions for that?
>
> Hello Brian,
>
> I'm not sure I understand what you are trying to achieve. Are you trying
> to spread the client load among replicas? If so, then I think the SRV
> records in DNS are really the best answer. You can organize the servers
> in "tiers" by using the priority field and then spread the load in a
> tier by using the "weight" field.

Greetings,

if I understand correctly, you need to set different priority for SRV 
records and this new priority has to be dependent on client's IP address.

AFAIK only way how to accomplish this is BIND "view" clause. You have to:
- create copy of original zone for each location and modify SRV record 
priorities
- then you have to set "views" and create mapping between IP address <-> 
new zone


This way requires multiple copies of original zone, each with little 
differences.
In case of classical zone files is not a big problem: You can keep SRV 
records separated in small files and "$INCLUDE" normal records to them 
from single place.

In cases with LDAP database it's a much harder, because there is no 
simple $INCLUDE clause, I think.
We have to consult this problem with 389 guys ... It can be task for 
some kind of directory server plugin.


Some examples and documentation:
http://wiki.sipfoundry.org/display/sipXecs/Location+based+DNS+views+for+sipXecs+using+BIND
(It belongs to some SIP solution, but it's exactly what you want.)

http://www.zytrax.com/books/dns/ch7/view.html

http://ftp.isc.org/isc/bind9/cur/9.7/doc/arm/Bv9ARM.ch06.html#view_statement_grammar


I'm adding BIND maintainer to this discussion.

Petr^2 Spacek