number of connections which nginx is waiting the resopnse from upstream

[foxgab]

according to the documentation of http_stub_status_module, there are 3 kinds
of connections show in the status page, but I'm confused that which kind the
connections, which are waiting or reading responses from upstream servers,
should be classified into ?

Posted at Nginx Forum: https://forum.nginx.org/read.php?2,275549,275549#msg-275549