[QGIS-Developer] [processing] launching separate process/thread

[Andreas Plesch]

I would like to launch a minimal web server from a processing script to
serve html properly (rather than using the file protocol).

Since the web server needs to run and keep running separately from qgis or
the qgis python interpreter, I investigated various ways to accomplish this
using SimpleHTTPServer. On windows 2.18.7 as linux should be more robust.

- threading.Threat : start() works until the server actually serves a file.
Then qgis crashes with a minidump . For some reason, the crashing happens
not always but more often than not.
- multiprocessing : seems to be the recommended solution but I do not seem
to have it with Qgis python (?)
- QProcess.start() : works from the python terminal, seems robust but does
not seem to work from a processing script (?). Would be the preferred
solution.
- QProcess.startDetached('python',(args),dir) : works reliably but requires
killing and restarting the process to change the root directory served

This may all change with Qgis 3 but I suspect 2.18 will be around for a
while, too.

Any recommendations or ideas would be welcome.

I will look into qgis2web to see what it does.

-- 
Andreas Plesch
39 Barbara Rd.
Waltham, MA 02453
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