Initial Map loading takes very long

[meyerlor]

As this thread ist stale and maybe not completely the right topic, i open a new issue

Uff, i thought i was running qgis-server 3.40.4 since quite a while (In Lizmap Admin it told me qgis-server 3.40 is recognized) but two days ago i had to restart my server and since then, the initialisation of my (heavy) project takes ~40 seconds. After the legend symbols are loaded, it is perfectly smooth.

I downgraded to qgis-server 3.34.15 - initialisation takes the same amount of time, but at least the legend symbols are then cached - closing the tab and opening again the same project leads to a loading time of ~6sec.

Should the thread be reopened? Or should i open a new ticket?

Originally posted by @meyerlor in #4750

Since QGIS Server 3.40.X project load in Lizmap takes significant longer. Legend symbols are also not cached anymore, so revisiting a LWC projekt will always download all legend-symbols first and therefore again it will take a lot of time to load the project.

[mdouchin]

We should look deeper :

• control a cache (client & server side) could be added
• see if another approach could be used to retrieve each layer legend

@meyerlor Do you have a project with data you can share (with enough complexity but non sensitive data) ?

[meyerlor]

Will provide one as soon I'm back from the FOSSGIS conference! :)

[gioman]

control a cache (client & server side) could be added

@mdouchin sorry for asking again, but there isn't a way to have the json legends pre-generated on the server or client side and avoid LMWC to have to get them generated by qgis server on project load?

[mdouchin]

@mdouchin sorry for asking again, but there isn't a way to have the json legends pre-generated on the server or client side and avoid LMWC to have to get them generated by qgis server on project load?

It could, but it is never simple to manage synchronization afterwards. For example, the editor saved a modified version of the project, containing new symbology classes, but does not save the Lizmap configuration with the plugin: this would lead to out-of-date list of symbols.

Imagine also some layers with a symbology depending on the variable @lizmap_user or @lizmap_user_groups. Such layers would need to have a different list of classes and symbols depending on the authenticated user.

We will look into it as soon as possible, but we really think this should be managed server side to be efficient and bullet-proof. I know this issue has been raised quite a long time ago, sorry for the lack of feedback.

[guenterw]

I had already reported the speed problems on discourse:
https://discourse.osgeo.org/t/speed-problems-after-update-to-qgis-server-3-40-4/113474

We have test projects, all on the same type of (very small) cloud server.

Once a quite small project ""Test BürgerGIS..." and once one with several, also non-existent, layers "Test WebGIS-Projekt Bauleitplanung ..." always with Lizmap 3.8.6

Under Apache with QGIS-Server 3.40.5
https://cx21-8.webgis.biz

With Apache and QGIS Server 3.34.15
https://cx22-34-8.webgis.biz
(loads significantly faster)

and with nginx and QGIS-Server 3.40.5
https://fossgis.gisgeometer.de/

Another project will follow from @meyerlor
Greetings from the FOSSGIS

[guenterw]

The difference in speed between 3.34 and 3.40 is particularly clear here

[SecondGIS]

Hi there,
you are pointing QGis-server version but from what I experimented here legend loading latency issues are related to LWC version (>3.6) whichever QGis-server version is used...

[gioman]

It could, but it is never simple to manage synchronization afterwards. For example, the editor saved a modified version of the project, containing new symbology classes, but does not save the Lizmap configuration with the plugin: this would lead to out-of-date list of symbols.

@mdouchin this does not seems a major issue to me, just issue a warning as it is already done when a new layer is added in a project that is already under LM "control".

Imagine also some layers with a symbology depending on the variable @lizmap_user or @lizmap_user_groups. Such layers would need to have a different list of classes and symbols depending on the authenticated user.

I didn't think about it, but seems a corner case. I understand that the right solution must cover all possible cases, but the bottom line is that right now there is an overall sense on slowness affecting any project that is not just 3 or 4 layers, and while it may have got a little better with the latest versions of LMWC and QGIS Server, is still very much an issue affecting many (also by looking at the several threads/comments on this matter here in the tracker).

Happy to chat about this in June in Sweden if you'll be there.

[meyerlor]

would it maybe be possible, to load the legends after the map layers?