see  http://sueboy.blogspot.tw/2017/11/nginx-proxy-pass-best-practices.html
http://sueboy.blogspot.tw/2017/11/nginx-proxy-pass-best-practices-2-for.html

server {
  listen 80;
  server_name aaaa.bbbbb.com;
  location /
    {
        proxy_http_version 1.1;
        #proxy_set_header Upgrade $http_upgrade;
        #proxy_set_header Connection “upgrade”;
        proxy_pass http://xxx.xxx.xxx.xxx:80;
    }
}

proxy_redirect off;
proxy_buffering off;
proxy_set_header Host $host;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header REMOTE-HOST $remote_addr;

proxy_set_header X-Original-Host $http_host;
proxy_set_header X-Original-Scheme $scheme;

proxy_set_header X-Real-IP $remote_addr;

proxy_set_header X-Forwarded-For $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header X-Forwarded-Proto $scheme;
proxy_set_header X-Forwarded-Port $server_port;

client_max_body_size 10m;
client_body_buffer_size 128k;

# client_body_temp_path /var/nginx/client_body_temp;

proxy_connect_timeout 90;
proxy_send_timeout 90;
proxy_read_timeout 90;
#proxy_send_lowat 12000;

proxy_buffer_size 32k;
proxy_buffers 4 32k;
proxy_busy_buffers_size 64k;
proxy_temp_file_write_size 64k;

# proxy_temp_path /var/nginx/proxy_temp;

proxy_ignore_client_abort on;

proxy_next_upstream error timeout invalid_header http_500 http_503 http_404;

proxy_max_temp_file_size 128m;