Currently its almost impossible to know which host actually handled the request, this extra variable logs the upstream server too
@@ -108,7 +108,8 @@ gzip_types text/plain text/css application/javascript application/json applicati
log_format vhost '$host $remote_addr - $remote_user [$time_local] '
'"$request" $status $body_bytes_sent '
- '"$http_referer" "$http_user_agent"';
+ '"$http_referer" "$http_user_agent" '
+ '"$upstream_addr"';
access_log off;