Nginx + Lua 實現動態更新後端節點，主動監控檢測方案：
1、nginx + upsync 模塊
https://github.com/weibocom/nginx-upsync-module
https://github.com/xiaokai-wang/nginx-stream-upsync-module 支持TCP轉發
https://github.com/CallMeFoxie/nginx-upsync
2、右拍雲的slardar
https://github.com/upyun/slardar
3. tengine + ngx_http_dyups_module
https://github.com/yzprofile/ngx_http_dyups_module
https://github.com/alibaba/tengine/blob/d271c477f9f8dd18411145853536cc947cc74e0d/docs/modules/ngx_http_dyups_module.md
http://www.ttlsa.com/nginx/nginx-modules-ngx_http_dyups_module/
4. consul nginx template
consul template定義nginx配置文件模版，從consul上讀取server信息(ip + port)，然後更新nginx,並reload nginx. 這些都是consul幫助實現的，不過還是有reload操作。
業務相關實現代碼：
https://github.com/easemob/SwallowKeeper
https://www.jianshu.com/p/59d7173c78a9