Cancel running algorithm in QGIS

Question

Running QGIS (using currently 3.14.1, but this happens in older versions as well) on Windows 10, I sometimes encounter the problem of a task (algorithm) running endlessly without the possibility to stop it. The only workaround is to force QGIS to close, losing temporary layers.
In this specific case, I started vectorize - it's running for two hours and I don't know for how long it will continue. I would like to change parameters and start it again. However, the Cancel button is not active.

There are other cases of tasks that I canceled, but they still continue to run in the background. So it seems to be a general issue of QGIS.
Is there a solution to cancel running algorithms without closing the program?

etrimaille · Accepted Answer

We see on your screenshot that you are using gdal_polygonize algorithm. There is currently no way to cancel GDAL/OGR based algorithms.
It works for QGIS based algorithms (provider native or qgis).
Algorithms must check regularly if the user has cancelled the operation, so it can take some time, depending of the background algorithm how it is built.
You can read this topic on the QGIS Dev mailing list explaining the situation : http://osgeo-org.1560.x6.nabble.com/QGIS-Developer-Cancelling-a-running-processing-model-td5443718.html#none

Cancel running algorithm in QGIS

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