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nextaccountic

Is inotify broken? What should be used instead of it to watch for filesystem events?

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http://wingolog.org/archives/2018/05/21/correct-or-inotify-p...

Thanks!

Does fanotify fix those issues?

Lose events due to inotify buffer overflow, or provide backpressure on entire vfs and allow a watcher to DoS the entire system. Pick one.

Similar "minor implementation issues" occur when considering how to fix all of the other "bugs."

It's fine if you don't like the design trade-offs of a particular solution. But pretending that they aren't trade-offs, or they aren't valid choices, is just going to leave people shaking their heads at you.

Edit: and by "you" i mean the authors of these articles. Although I think Marek is a very talented guy and probably just a bit hyperbolic with his titles.

I don't know man, I've given up and handed it over to someone more senior. Their port was half the performance and the project was killed. We kept on using FreeBSD for the product.

Is it broken regarding to correctness or just performance? I mean, does inotify have some obscure race condition or drop events or duplicate events or something

> Is it broken regarding to correctness or just performance?

Yes.

This blog entry explains it much better then I could: https://wingolog.org/archives/2018/05/21/correct-or-inotify-...

For watching filesystem events FreeBSD's kqueue is much more difficult to use correctly though, and in my experience it certainly doesn't outperform inotify.

inotify (and now, fanotify) are specifically designed to watch for filesystem events, whereas kqueue is a generic event system used for many things. In many ways that's better, but it this lack of specialisation also comes with some drawbacks.

From what I can recall, the performance issues were on the network side. I suspected accept() calls not scaling right, but instrumentation on Linux was quite poor at that time. They had nothing like dtrace back then so I can't be certain.

Jesus, is it sad when I hear senior now I don't dream of leading the design of big systems?

I think of stakeholder meetings and fighting business requirements?

I had an inotify project in process for creating a better developer experience. Seeing this hit Hacker News tells me it's a fucking political landmine.

Sigh.

Don't worry, I'll have the strength to argue the proper technical solution that still satisfies business needs. That's the important thing!

I don't understand what you mean.

Anyway I used inotify multiple times in various programming languages and it was always fine, I'm a bit surprised that it's considered "broken" in any way.

I mean, is it broken regarding to correctness or just performance?

I don't consider it broken, I was referring to political will to build the healthy base of a developer ecosystem.

But, you've inspired me to do a deeper historical and technical deep dive of the filesystem event space. Thank you.

Have a great weekend!

And I do understand. I am one who reached out. Thank you for showing me.

They understand who I am.

Have a good week!

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