time to read packets for HTTP query

[Lukas Tribus]

Hi,


> I'm running a SAAS service running via NGINX and have been running tcpdump
> to look at the incoming packets for HTTP queries. Many of the HTTP queries
> are bigger than the MTU of 1,500 bytes and therefore arrive as 2, 3, or 4
> packets. I noticed that for some customers there are significant delays
> between packets. The average size of these delays acts as a kind of
> fingerprint for each customers. The inter packet delay various from a few
> milliseconds to 100ms plus! Some customers have no delay. There are all
> shades of grey.
>
> When processing a SAAS query I log how long the processing time took etc. So
> it would be useful to log how long NGINX took to read the HTTP query packets
> too. Using tcpdump and a script to analyze the packet dump is not very
> handy. So I'm wondering if there is a mechanism in NGINX to report somehow
> the total time necessary to read all the packets of a particular HTTP query?
> I was thinking that if available, I could add it to the HTTP query in the
> form of an HTTP header? If not, how easy would it be to implement such a
> mechanism?

What about $request_time [1]?

Lukas


[1] http://nginx.org/en/docs/http/ngx_http_core_module.html#var_request_time