Given the format and the informations provided in the sample log entry posted in the question the huge log file has nothing (directly) to do with nginx nor with its configuration files, despite it's located in
....access.log file is written by php-fpm worker processes when a specific option is set into php-fpm's configuration file
The file (on my server) is located into
At some point in the configuration file there is:
; The access log file ; Default: not set ; access.log = /usr/local/nginx/logs/$pool.access.log
By default that option is not set and should remain unset; as far as I know the log file it produces is used to test php-fpm proper operation.
If the line is uncommented by removing the semicolon...
; The access log file ; Default: not set access.log = /usr/local/nginx/logs/$pool.access.log
.access.log file prefixed with the pool name (
www in the case exposed in the question) is generated. And it grows quickly as each time a php script is run due to a request a new log entry is appended.