about request_time and upstream_response_time

[yt]

Hi all,

     My site's architecture likes this: nginx (upstream) ->  apache (image process),
apache processes a picture and consumes about 0.030 seconds, that is to say,
upstream_response_time is about 0.030 seconds. However, nginx's request_time
always more than 2 seconds. And , I know, the request_time include receiving
request time, processing time, and sending response time, but I don't know why
my nginx's request_time is so much too higher than upstream_response_time?


Best regards,
yt