How nignx handled the header to the client in this situation

[allenhe]

Hi Francis,

Thanks for the reply!
w.r.t. the "http://nginx.org/r/proxy_buffering", the doc does not mention if
the buffering works for header, body or both, I'm wondering if nginx can
postpone the sending of upstream header in any ways? otherwise the client
will get wrong status code in this case.

Allen
BR

Posted at Nginx Forum: https://forum.nginx.org/read.php?2,287990,288056#msg-288056