proxy_cache_lock stat under log (no replies)

Hi,

We are using proxy_cache_lock feature of nginx and have set proxy_cache_lock_age and proxy_cache_lock_timeout attributes.

To monitor and get overall stats we are looking for nginx log generated and any option to add some proxy cache lock based numbers to log entries.

Some info about request being on hold or time wait under proxy lock criteria and time spent for the same.
Any input will be really appreciated.

Regards,
Yogesh