Let's see the meaning of request_time and upstream_response_time in stress testing, request_time
request processing time in seconds with a milliseconds resolution; time elapsed
between the first bytes were read from the client and the log write after the last
bytes were sent to the client
upstream_response_time
keeps time spent on receiving the response from the upstream server; the time is
kept in seconds with millisecond resolution. Times of several responses are
separated by commas and colons like addresses in the [$upstream_addr]
(http://nginx.org/en/docs/http/ngx_http_upstream_module.html#var_upstream_addr)
variable.
so with these two variables record in request log, we can calculate time spent in upstream server and in nginx repectively. The bottleneck may be found in nginx or upstream server. For example, if upstream_response_time is small, but request_time is very large, even timeout in some conditions, it is a hint that the nginx server working as gateway is a bottleneck.
