On Wed, Jul 20, 2011 at 02:18:52PM -0700, Matthieu Tourne wrote:
> Hi all,
>
> I was looking at the code in ngx_http_upstream_ip_hash_module.c
> And I'm not sure where the hashing algorithm for IPs is coming from,
> especially those lines :
>
> iphp->hash = 89;
>
> hash = (hash * 113 + iphp->addr[i]) % 6271;
>
> Just wondering if those constants are arbitrary chosen, or if there is
> something there to guarantee a good distribution ?
>
> If you have some links explaining this algorithm, it would be greatly
> appreciated!
> Also, how would you get a good distribution on IPv6. Maybe it would make
> sense to use murmur ?

This algorithm came from FastMail.fm. Murmur2 may be better, I'm going
to use it in upcoming upstream hash module which allows to hash any
expression.


--
Igor Sysoev

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