Adding cachekey to log_format directive

[Wouter van der Schagt]

Hi Graham,

Thank you for your reply, the r->cache->file.name was particularly useful
for this use-case, thank you for the insight!

Sincerely,
- Wouter van der Schagt

Posted at Nginx Forum: http://forum.nginx.org/read.php?2,232747,233189#msg-233189