Per the man page, A successful call to inotify_add_watch() returns a unique
watch
descriptor for this inotify instance, for the filesystem object
(inode) that corresponds to pathname.That implies that if the inode
doesn't exist yet, then the watch doesn't work. I'm pretty sure it won't keep
checking for it to start existing, then grab the inode.
So, I think filtering out watches for things that don't exist yet is probably
the right answer.
On Tuesday, March 20, 2018, 2:31:50 PM EDT, H. William Welliver III
<will...@welliver.org> wrote:
I guess what I was looking for was an answer to whether or not it is a design
feature to be able to create monitors on folders that don't exist. I was
planning to ensure that new monitors have valid stat objects on creation. That
way, if the directory is gone by the time the monitor attempts to create a
monitor object for the folder, it will throw an exception and not end up
hanging around.
If, however it's intended that a monitor could exist for something that doesn't
exist yet, I don't think that my plan can be used to mitigate the problem. I
think then that the only real solution would be to filter out non-existent
paths from within the inotify callback.
Any thoughts?
March 17, 2018 2:56 PM, "H. William Welliver III" <will...@welliver.org> wrote:
Yes, that’s true, but (I think) the problem here is that the monitor is being
created without there being a valid stat object, so the stat comparison never
changes. I think that if it was at least initially populated with some stat,
subsequent checks would detect it.
On Mar 17, 2018, at 2:20 PM, Lance Dillon <riffraff...@yahoo.com> wrote:
Unless the action is atomic, there is still no guarantee that the path will
exist between the time you check and when you set the monitor.
Sent from Yahoo Mail on Android
On Sat, Mar 17, 2018 at 12:28 PM, H. William Welliver III
<will...@welliver.org> wrote: I’ve noticed that when using Filesystem.Monitor
on a system with inotify there is the possibility of monitors being created on
paths that don’t exist. Specifically, if a directory is created and deleted in
very rapid succession, the inotify events are processed after the directory is
already gone. The resulting Monitors hang around forever (with their associated
polls). It doesn’t appear that any events get triggered for this situation,
though I can’t be absolutely sure because I’m not watching for directory
changes. My concern is that these phantom monitors can build up over time.
Does it make sense to check for the existence of something before monitoring
it? I didn’t want to assume that was desirable because I suppose it’s possible
someone might want to watch with the expectation that it will exist later…
(maybe?) Bill
