webapp: use multithreaded server to avoid 'hanging' requests

[davidHarwardt]

Loading a page in the webapp sometimes incurs a significant loading delay.
The issue isn't perfectly reproducible but occurs often enough to be a problem.

Due to a problem with Chromium (and presumably other major browsers) mentioned here:
https://issues.chromium.org/issues/40978518
the single threaded webserver used by sedrila deadlocks with the browser until a timeout is reached.
The Chromium issue is marked WontFix thus we'll probably have to use a concurrent server implementation.

A temporary fix with a shorter timeout is already implemented.

[prechelt]

Super. We knew the phenomenon for a long time, but nobody had a good idea how to debug it. Thanks.

The next step is probably to make the webserver underlying bottle multi-threaded.
https://bottlepy.org/docs/dev/deployment.html describes how to do that, it does not sound too complicated.
Which server to use?

• rocket (which I had not even heard of before) had its last release in 2017.
• paste is being phased out (doing only the barest minimum of maintenance)
• cherrypy is looking good: https://cherrypy.dev/ , https://github.com/cherrypy/cherrypy , https://pypi.org/project/CherryPy/
• tornado or twisted might also be options.

I vote for whatever seems lightest and/or easiest to use.