[Qgis-user] Qgis crashes while loading WMTS layers

[Patrick Dunford]

Hi there

Due to imminent deadlines on a project I was working on, I had to leave 
the issue and just press on with a VM running an older version.

I am currently building some test VMs and projects and hope to log this 
issue in the bug tracker in the next few days.

On 2/02/20 5:25 am, Jonathan Moules wrote:
> Hi Patrick,
>
> I'd suggest reporting this to the QGIS bug tracker as a regression.
>
> Cheers,
>
> Jonathan
>
> On 2020-02-01 07:20, Patrick Dunford wrote:
>> 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.
>>>
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