<div style="line-height:1.7;color:#000000;font-size:14px;font-family:Arial">The Nginx document said that there are two upstream-related directives introduced in the version of 1.15.3:  "keepalive_requests" and "keepalive_timeout".  But the directive "keepalive" has already been instroduced in the version of 1.1.4. So I want to know how does Nginx handle the keepalive connections for upstream before the version 1.15.3 was released. When will the keepalive connections for upstream be closed?</div><br><br><span title="neteasefooter"><p> </p></span>