How to log the correct Ip having Varnish and Nginx

When you run a webserver behind a reverse proxy or HTTP accelerator such as Varnish, the webserver access logs will display the IP of the proxy (generally instead of the end user’s IP.
This is a problem when you have a software like webalizer, awstats or similar log file analysis program, because you lose one of the most important information: ???Who is the requestor of a page ????, also having all the access coming from the same IP ( you lose information such as ???what’s the browsing pattern of visitors ???? ???Is someone trying to do something Nasty ????

In this small how-to I’ll show how to put this information back on your Nginx log files in 2 different ways.