專案中Nginx多級代理是如何獲取使用者端的真實IP地址

log_format  main  '$remote_addr - $remote_user [$time_local] "$request" '
                  '$status $body_bytes_sent "$http_referer" '
                  '"$http_user_agent" "$http_x_forwarded_for"';
access_log  /var/log/nginx/access.log  main;

10.0.3.137 - - [09/Oct/2020:09:41:02 +0800] "GET / HTTP/1.0" 304 0 "-" "Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; rv:11.0) like Gecko" "10.1.9.98"

#!/bin/bash
#紀錄檔檔案存放目錄
LOGS_PATH=/usr/local/nginx/logs
#備份檔名稱
YESTERDAY=$(date -d "yesterday" +%Y%m%d%H%M)
#重新命名紀錄檔檔案
mv ${LOGS_PATH}/access.log ${LOGS_PATH}/access_${YESTERDAY}.log
mv ${LOGS_PATH}/error.log ${LOGS_PATH}/error_${YESTERDAY}.log
## 向 Nginx 主程序傳送 USR1 訊號。USR1 訊號是重新開啟紀錄檔檔案
kill -USR1 $(cat /usr/local/nginx/logs/nginx.pid)

# crontab -e
*/1 * * * * /bin/bash /usr/local/nginx/logs/nginx_log.sh

worker_processes  1;

events {
    worker_connections  1024;
}

http {
    include       mime.types;
    default_type  application/octet-stream;
    log_format main '$remote_addr - $http_x_forwarded_for - $http_x_real_ip';
    access_log  logs/access.log  main;
    server {
        listen  80;

        location / {
                # proxy_set_header X-Real-IP $remote_addr;
                # proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
                proxy_pass http://10.0.4.105;
        }
    }

}

...
        location / {
                # proxy_set_header X-Real-IP $remote_addr;
                # proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
                proxy_pass http://10.0.4.129;
        }
...

...
        location / {
                # proxy_set_header X-Real-IP $remote_addr;
                # proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
                proxy_pass http://10.0.4.120;
        }
...

...
        location / {
                root html;
                index index.html;
        }
...

# 類似nginx中的$remote_addr
request.getRemoteHost();

request.getHeader("x-real-ip");