Re: Algorithms and Hashing (was: Re: Reread of config without restart)

From: Michael Rennt <>
Date: Thu, 13 Mar 2008 11:21:53 +0100

Patrick Viet wrote:
> 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.

This is what I did yesterday before sending the mail. I just didn't test source persistence together with cookie persistence.

I see that y'all rather use the source option in combination with a persistency cookie.

Let me explain why I was asking this question: We are running a different software for a customer for 4 years now in a cluster with 100+ machines. On some VIPs he's using source persistence only, because cookies are not applicable.

This is the background why I'm afraid that a new server will mess up the stickyness.


Michael Received on 2008/03/13 11:21

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