keeyong Wrote:
-------------------------------------------------------
> I am wondering if it is possible to compute some kind of hash value
> from ip address or do modulo operation on the last numeric value from
> ip address (for example on 24 given 172.16.4.24)? Based on this, I
> want to send the request to different endpoints (not to different
> servers). If this can be done without installing any new module, that
> would be the best.
>
> As far as I can see, I feel like I should do something similar using
> the regex?

Yes, regex and map should help. If you want to derive four distinct values, you can do something like this:

map $remote_addr $key {
~\.[0-9]$ 1; # 0..9
~\.[0-5][0-9]$ 1; # 10..59
~\.6[0-4]$ 1; # 60..64
~\.6[5-9]$ 2; # 65..69
~\.[7-9][0-9]$ 2; # 70..99
~\.1[0-1][0-9]$ 2; # 100..119
~\.12[0-8]$ 2; # 120..128
~\.129$ 3; # 129
~\.1[3-8][0-9]$ 3; # 130..189
~\.19[0-2]$ 3; # 190..192
default 4;
}

Caveats: This does not work for IPv6.

I have no idea if the fourth IP byte is normally distributed. If not, then may generate a full mapping (~\.1$, ~\.2$, ... ~\.10$, ..., ~\.99$, .., ~\.255$)

If you want to do something even more fancy you can go totally binary with the $binary_remote_addr variable and \xYY in the regexp (never tried this as it is more difficult to debug).

Oliver