In version 1.0.2 of redislog module I added a feature that allows you to do conditional logging. What can you do with it? For example, logging only unique visitors. E.g.:
userid on; userid_name uid; userid_expires 365d; access_redislog test "$server_name$redislog_yyyymmdd" ifnot=$uid_got;
$uid_got becomes empty whenever a visitor doesn’t have an UID cookie. Therefore, this directive effectively logs all hits of unique visitors. You can populate a list (one per virtual host and day or hour) with unique visitor records and count them with LLEN. For that just use LPUSH command instead of default APPEND. Details could be found in the manual.