让nginx后端访问日志显示真实ip

架构：前端两台nginx做负载，后端real server，nginx作为web服务器，还会用到apache
目的：让后端nginx的访问日志显示真实ip，以便于统计
配置：
    前端：

server {

        listen       80;
        server_name  xxx.com;

        access_log  /data/logs/access.log  main;
        error_log  /data/logs/error.log;

        location / {
            proxy_pass http://abc_server;
            proxy_set_header   Host             $host;
            proxy_set_header   X-Real-IP $remote_addr;
            proxy_set_header   X-Forwarded-For $proxy_add_x_forwarded_for;

        }

    }

    nginx后端：

http {

    include mime.types;

    default_type  application/octet-stream;

    log_format  main '$http_x_forwarded_for - $remote_user [$time_local] "$request" '
                      '$status $body_bytes_sent "$http_referer" '
                      '"$http_user_agent" "$http_x_forwarded_for"'

apache后端：
http.conf中添加

<IfModule log_config_module>
    #
    # The following directives define some format nicknames for use with
    # a CustomLog directive (see below).
    #
    #LogFormat "%h %l %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-Agent}i\"" combined
    LogFormat "%{X-Forwarded-For}i %l %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-Agent}i\"" combined
    LogFormat "%h %l %u %t \"%r\" %>s %b" common

CustomLog "|/soft/apache/bin/rotatelogs /data/httplogs/access.%Y%m%d 86400 +480" combined