Re: Algorithms and Hashing

From: Guillaume Bourque <>
Date: Thu, 13 Mar 2008 08:22:51 -0400

Patrick Viet a écrit :
> On Wed, Mar 12, 2008 at 8:10 PM, Michael Rennt <> wrote:
>> I see that the server identifier is stored inside the cookies. This is pretty
>> good, as it keeps stickyness even when there's a failover to another equally
>> configured loadbalancer.
>> The only question left for now: How is all the hashing and distribution implemented?
>> I see that the source IP (or whatever other parameter) is hashed and divided by
>> the total weight of all servers. But what if a new server is added?
>> Won't the stickiness be completely different after that, messing up any existing
>> stickiness?
> The hashing choice is done only if there isn't already a persistency cookie.
> Therefore the old sessions don't move, and the new sessions will
> benefit from the extra server.
> You should really try the software. Nothing beats experience.
> Patrick

I was asking this because we are using tcp mode which don't use cookie for persistency so the only thing that is important, I think, is to define the backend server in the same order on my 2 haproxy. That way a particular client with is hash will always end up on them same backend server.

I will do more testing but in tcp mode the important thing in a ha setup is to define alle the server in the same order.

I'M correct here ?


Guillaume Bourque, B.Sc.,
consultant, infrastructures technologiques
Logisoft Technologies inc.
514 576-7638
Received on 2008/03/13 13:22

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