IP Upstream Hash

Matthieu Tourne matthieu.tourne at gmail.com
Wed Jul 20 21:18:52 UTC 2011


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 ?

Thank you,

Matthieu.
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