Use 'watchgod' module instead of 'watchdog'

I’m just starting to use Lektor but i noticed that it uses the watchdog module and one of the first comments that i saw at the quickstart tutorial was:

When I run lektor server I get OSError: inotify watch limit reached

I ran into that myself and thus i know what it is and that it’s related to watchdog but a lot of beginners probably don’t know. Instead of using separate approaches for each OS to watch for file-changes, i think that using the watchgod module could be a better and simpler solution.

Maybe it’s a good idea to at least check the module out and see if it fits better than the overly complex watchdog implementation.

[dairiki]

Hitting the inotify limits is a system problem, not a Lektor problem — sometimes even tail -f won’t run in this case — but it would be good if Lektor would degrade gracefully when this happens.

The watchdog distribution provides several different types of “Observers” that can be used to watch for file changes. On Linux, the default observer is InotifyObserver. There are other observers which are used on different OSes, but watchdog also provides a PollingObserver, which — while not as efficient as the other observers — should work anywhere.

From looking at the Lektor code, it appears that Lektor does not catch exceptions when creating the default (InotifyObserver on Linux) observer, so if that fails the server just craps out.

We should catch errors when creating the default observer, report them with a big warning, and then fall back to using PollingObserver.

[yagebu]

Yes, that error sounds like it is related to file watching. Does it crash the server or does it just show this error message and work as expected?

I understand that the “one size fits all” approach of watchgod sounds appealing, but I don’t think that it would be a good choice for Lektor. Watching for file-changes is inherently platform-specific (by using inotify, fsevents, etc., which watchdog does) or inefficient (by using polling, which watchgod and which is also offered by watchdog). Also, after having looked rather dead for a while, the watchdog repo has gotten more active recently and there’s frequent releases, so I think that’s also not an argument against watchdog anymore.