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Upstream Keepalive Nginx Module
Yichun Zhang , 26 Aug 2011 (created 21 Jun 2011)This is a keepalive balancer module for nginx that implements cache for backend connections.
Documentation: https://nginx.org/en/docs/http/ngx_http_upstream_module.html#keepalive
Project page: http://mdounin.ru/hg/ngx_http_upstream_keepalive/