[Qgis-developer] [Server] performance questions

[Andrea Peri]

I Guess the time difference between the qgis desktop and qgis-server
when using a postgres,

is due to the protocol.
Infact the http is a connection-less session-less protocoll,
so after every map the qgis-server disconnect from postgres.

Instead when you work on a qgis desktop as a user on its own pc you
are connectin with a postgres and sray connected for all the time.

So the postgres don't waste time to open and staryup your connection.

Also don't forget that if you stay about 18-20 minutes without do
nothing on qgis in a postgres connection.
The postgres kill your connection and your qgis go in crazy state.

A.


2016-02-23 15:20 GMT+01:00 Régis Haubourg <regis.haubourg at eau-adour-garonne.fr>:
> Hi all,
> we are working on using qgis server here and we face some performance issues
> on big data sets. Cache is not an option for those layers that will be
> edited by users. Currently performances are not acceptable for production
> uses.  Here is a couple of questions that I could not answer by myself on
> the net:
>
> 1- Clarifying multithread on server side vs multithread on desktop:
>
> We use qgis 2.12 server from qgis repository for debian on a 4 core Xeon
> (2.1Ghz) + 16Go RAM.
>
> We configured apache2 with MPM worker and we have a pool of 10
> qgis_mapserv.fcgi waiting for client request.
> The behaviour here is that one client will only consume one fcgid process,
> when desktop can use several processes to make some parallel rendering of
> project layers.
> When having QGIS desktop  using only one thread, I have similar rendering
> time. The difference is purely proportionnal to CPU speed difference.
> Did we miss something in configuration process or is that the intended
> behavior? I did try to use QGIS_OPTION_PATH on a QGIS2.ini but I really
> can't be sure it is really being used.
> Do QGIS packages miss the multithread option on compile cmake options?
> If this is expected, does the web architecture would allow to have fcgid do
> parallel rendering like desktop? Would that be a big work (I could partly
> fund that)?
>
>
> 2- Overhead on first request with postgres complex view compared to
> shapefiles
>
> We have almost only postgis views being used as QGIS layers. Qgis server
> builds get capabilities and requests views to get extent and primary keys.
> There is a severe overhead for the first wms request by a client session.
> When generating the image takes about 7s, the first request can take from 24
> to 30s. Desktop multihreaded will get the image in about 3s (same postgres
> server, same network).
> That overhead starts to become annoying on desktop side too, but it's only
> qgs loading time, once in a work session. Does someone have any idea that
> one day postgis could collect such metadata on views so that QGIS do not
> have to scan all rows when data are in views? Direct access to tables, or
> same project with shp datasources do not show that overhead on server nor in
> desktop.
>
>
> Thanks for your hints,
> Cheers
>
> Régis
>
>
>
> --
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-- 
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Andrea Peri
. . . . . . . . .
qwerty àèìòù
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