[Qgis-user] Qgis crashes while loading WMTS layers

[Patrick Dunford]

Further investigation and comment

Since recently installing Qgis 3.4.15 or 3.4.14 on some of my computers 
running Debian 10, I immediately began to see a trend of the software 
exhibiting an increased tendency to crash when working with certain WMTS 
layers that I had previously worked with extensively over recent weeks 
for mapping purposes.

After attempting numerous changes including special versions of projects 
containing no file based raster layers and only containing one WMTS 
layer at a time and being unable to use the software regardless I 
created a virtual machine running Debian 9 which has the latest version 
available for that platform, 3.4.4. This has resulted in immediate major 
improvement in the reliability of the software to the point I can resume 
using it without the numerous crashes of the software that have been 
noted recently, especially in the last week approximately.

On 27/01/20 1:19 am, Patrick Dunford wrote:
> Good day to all.
>
> Not so long ago I wrote a post about issues handling large numbers of 
> raster files. This results from what appears to be an architectural 
> design limitation of Qgis in that it only has enough resources 
> available for a certain (unknown) number of raster layers and does not 
> have any effective system for dealing with the exhaustion of these 
> resources.
>
> I also noted that the software does not appear to have the ability to 
> use the swap (virtual memory) resources within a system to deal with 
> the apparent exhaustion of resources, as other software would. For 
> example, Gimp which I use for graphical editing is able to handle 
> certain projects using a swap space of 200 GB, which consists of 32 GB 
> of physical RAM and the rest in SSD. It is not unusual with some of 
> these graphics projects to have 100 GB or more of swap space in use, 
> without crashing the system. (This being possible since Gimp 2.10 with 
> its ability to write files of more than 4 GB)
>
> Whilst it is possible to manage the number of layers with file based 
> rasters, this cannot be done with a WMTS server because there is no 
> way I am aware of to manage the number of layers that can be 
> downloaded from the server.
>
> Version 2.18 and earlier almost never crashed with excess layers, 
> usually all that would happen is a layer would be displayed with 
> invalid data. However, crashes have become the norm with 3.x versions 
> of software.
>
> It seems to me there is a big architectural problem in the software 
> with its inability to utilise the full resources of the system in 
> order to process the number of layers that a WMTS server is capable of 
> issuing.
>