1. Detecting Googlebot
2. Logging the requests

#Detecting Googlebot

It's very easy to detect the Googlebut using the user agent in nginx, here we use the map directive to set the variable $googlebot to yes or keep it empty depending on the given user agent:

map $http_user_agent $googlebot {
    default "";
    "~*googlebot" "yes";
}

#Logging the requests

When $googlebot is filled, we want to log the request in a log file. This can be done using the access_log directive:

access_log /var/www/logs/googlebot.log bots if=$googlebot;

That's it!

You can read here how you can log multiple bots how to log multiple bots for your virtual host in nginx.