So, I need to monitor a fairly large nested directory tree for changes on Linux. It seems like there are a few different watcher modules that I could use – fsnotify and notify being the main ones, both of which use the inotify interface and attempt to set watches on each individual subdirectory and maintain all their watchers as things change. I have way too many directories for that to be a workable approach. It looks like the underlying issue is just that this is a difficult problem on Linux; both inotify and fanotify have some issues which make them difficult for library authors to use to present a clean and useful API.
Long story short - I coded up an fanotify-based solution which seems like a good start of what I need, and I’m planning on sharing it back in the hopes that it’s useful. I guess my question is, did I miss something? Is there already an easy and straightforward way to monitor a big directory for changes?
Just looking briefly it looks like it uses inotify (which definitely won’t work; I don’t have a super heavy write load but I have a total of 124,000 subdirectories to monitor) or can fall back to polling (which I could do myself without having to involve a library).
Why this app is constructed to store its stuff in 124,000 subdirectories is a separate issue but one that I can’t immediately snap my fingers and make go away, unfortunately.
124,000 subdirectories is a separate issue
Yeah sure, but that’s also not for discussion here.
Would it solve the issue by finding the limit of how much inotify can handle and then running multiple instances of a watcher on a subset of directories?
Say, inotify can deal with 1000 subdirs, so having 124 instances running should in theory be equal in resourse usage as if it would monitor 124k subdirs, give or take.
Just a thought tho 🤷♂️
I think inotify’s limit is per system… and even if it wasn’t, why would I want to take on the artificial challenge of keeping up with making sure all the watchers are set on the right directories as things change, instead of just recursively monitoring the whole directory? The whole point of asking the question was “hey can something do this for me” as opposed to “hey I’d like the opportunity to code up for myself a solution to this problem.” 🙂
