Strange requests stalling inside nginx

[MichaelLogutov]

Maxim Dounin Wrote:
-------------------------------------------------------
> Hello!
> 
> On Sat, Feb 11, 2017 at 04:06:29PM -0500, MichaelLogutov wrote:
> 
> > Hello.
> > We have some strange issues when requests seems to stall inside
> nginx - in
> > nginx log we see that request took 1 second (and was terminated by
> client
> > timeout), while excactly the same request (we have special unique
> headers to
> > mark them) from the uwsgi logs took only 100ms to complete.
> 
> It is not clear how do you measure that request took 1 second.  
> Note well that request time as seen by nginx is unlikely to be 
> less that the time seen by your backend, but can easily be much 
> longer: for example, nginx has to read the request from client, 
> and it sometimes takes significant time.
> 
> > We also saw some very strange pauses in nginx debug log:
> 
> [...]
> 
> I don't see any "strange pauses" in the logs provided.  If you 
> think there are any - please elaborate.
> 
> Note well that it's almost impossible to analize debug logs for 
> pauses if these logs doesn't contain information about processing 
> of events.  To make sure all needed information is present it is 
> important to configure debug logs at global level, as recommended 
> at http://nginx.org/en/docs/debugging_log.html.
> 
> -- 
> Maxim Dounin
> http://nginx.org/
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Thank you.
I was talking about 3 seconds gap here:

2017/01/26 20:17:51 [debug] 2749#0: *75780960 http upstream recv(): -1 (11:
Resource temporarily unavailable) 
2017/01/26 20:17:54 [debug] 2749#0: *75780960 http upstream request:
"/api/info/account/type/278933/?"

Posted at Nginx Forum: https://forum.nginx.org/read.php?2,272357,272371#msg-272371