PollingObserver misses some new files when previously seen files are removed

[smola]

I'm observing missing events for newly created files in the following scenario:

• Process 1 is creating files in a directory.
• Process 2 is observing the directory with PollingObserver, whenever it sees file X, it creates X.processed and removes X.
• Tested on Linux with ext4.

Here's a gist with code to reproduce the issue: https://gist.github.com/smola/d40614a9b546a650d87bc3588efc1014

Apparently, under these fast create/deletes, the operating system is reusing inodes for new files, and they are being detected as file moves, rather than creations:

watchdog/src/watchdog/utils/dirsnapshot.py

Lines 112 to 117 in 48c49a1

	for path in set(created):
	inode = snapshot.inode(path)
	old_path = ref.path(inode)
	if old_path:
	created.remove(path)
	moved.add((old_path, path))

However, the moves are arbitrary. For example, it detects a move from 87 to 83.processed. A possible workaround is looking for creation, modified events, and also moves (with dest_path in this case).

[smola]

I realize that that the problem of distinguishing remove/create with reused inodes vs file move is simply not solvable. But it seems something else is off in this scenario, where file modified events are also created for all files that were already deleted.