https://ma.ttias.be/enable-keepalive-connections-in-nginx-upstream-proxy-configurations/ 前提条件として Nginx > 1.1.4 が必要。http://qiita.com/toritori0318/items/a85d0b1efbd3ea1fc950 http://blog.nomadscafe.jp/2012/02/nginx-11x-httpupstream…