[Qgis-psc] (QGIS 2020 Grant Report) QGIS Server and performance monitoring

[Paul Blottiere]

Hi Andreas,

> Paul: can you clarify if you tested "sequentially" without parallel
requests? To me, if I interpret it correctly, this seems to be the case
here. Are you doing 20 subsequent, sequential, requests?

Yes there aren't scenarios with parallel requests. As soon as you have
parallel requests, you need several QGIS Server instances and a load
balancer (because a QGIS Server instance is able to address 1 request at a
time). So in this case, you don't test the nominal behavior of QGIS Server,
but the response time of the whole "infrastructure".

And in case of the QGIS-Server-PerfSuite, we want to check the rendering
time for a specific request.


> In the Solothurn benchmarks that Marco did, we almost always did parallel
requests - and we found out that the threaded rendering slows down
rendering if you have a lot of parallel requests, whereas, if you have no
or only 2-3 parallel requests, the threaded rendering is faster. In
general, in reality we often have 5-15 parallel requests in our
organization in Solothurn.

If you have too many instances of QGIS Server with the parallel rendering
activated, then you won't necessarily have enough cores to process the
rendering efficiently in case of parallel requests. In this case, it may
even lead to performance issues but it's not an issue with QGIS Server
itself.


Regards.
-- 
Paul Blottiere
QCooperative: https://www.qcooperative.net/
Hytech Imaging: https://hytech-imaging.fr/
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