Re: [lvs-users] FQDN as Real Server reference

To: " users mailing list." <lvs-users@xxxxxxxxxxxxxxxxxxxxxx>
Subject: Re: [lvs-users] FQDN as Real Server reference
From: Graeme Fowler <graeme@xxxxxxxxxxx>
Date: Sat, 28 Feb 2009 11:19:11 +0000
On Fri, 2009-02-27 at 21:37 -0600, Stjohnson wrote:
> Both of you are right on. I think you both understand. FQDN for Real server
> definition, not IP. So For load balancing, the LVS has to do a DNS query.

You're quite right in thinking that LVS won't do that.

> The ipvs does show dns names, but it's a reverse query, not so much
> responsible for the allocation of load.


> So it's looking like I'm not going to be able to do this LVS. I'm
> investigating other solutions actually just to cover all my bases. There has
> to be a system that does this w/o special modifications.

If this is for web services, you could use Squid. What you're really
after is a proxy, not a load balancer per se. Note however that in most
cases this sort of application will be running on an OS which caches the
results of DNS queries for a while (depending on config)  - the inbuilt
resolver in glibc might do this, plus the queried nameservers tend to
deliver the same result and many apps use the first result they receive.

If you're looking to do something whereby you automatically add/remove
hosts as realservers without having to modify the load balancer
itself... I'm not aware of one. Sorry!

>From a different perspective, this doesn't seem like a very efficient
way of handling incoming queries - a lookup for every "hit"? Do you mean
every connection, or every single packet?


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