libuv, osx and fsevents

[curtis...@gmail.com]

As far as I can tell, libuv on OS X uses FSEvents to watch directories but kqueue to watch files, resulting in one open fd per watched file.  Combined with OS X's insanely small default fd table, this makes it tough to build a dropbox style sync utility on top of libuv.

The FSEvents doc says that since 10.7, FSEvents can watch files as well as directories.  But the libuv code still seems to test for S_IFDIR and otherwise goto fallback (kqueue).

I'm wondering whether a pure FSEvents file watcher isn't in libuv because it wouldn't work for some reason, or because it's just a low priority.  If the latter, I'd be happy to try and come up with a patch.

[Saúl Ibarra Corretgé]

Hi,

On 06/02/2015 02:21 AM, curtis...@gmail.com wrote:
> As far as I can tell, libuv on OS X uses FSEvents to watch directories
> but kqueue to watch files, resulting in one open fd per watched file.
> Combined with OS X's insanely small default fd table, this makes it
> tough to build a dropbox style sync utility on top of libuv.
>

FAIS we still open an fd when FSEvents is used, which should be solvable.

> The FSEvents doc says that since 10.7, FSEvents can watch files as well
> as directories. But the libuv code still seems to test for S_IFDIR and
> otherwise goto fallback (kqueue).
>
> I'm wondering whether a pure FSEvents file watcher isn't in libuv
> because it wouldn't work for some reason, or because it's just a low
> priority. If the latter, I'd be happy to try and come up with a patch.
>

Fedor can probably give you a better answer, but probably it has to do
with the fact that OSX < 10.7 is still supported (ish). Personally, I'm
open to the debate of dumping support for OSX < 10.8, but we should
probably preserve it in v1.x, dumping it in master should be fine though.

You're more than welcome to write a patch for it and improve it, of course!


Cheers,

--
Saúl Ibarra Corretgé
bettercallsaghul.com

[Curtis Yarvin]

Yes, it looks like that fd is opened just because there's an fd field in the handle and otherwise it could get lonely ;-)

There are already OSX version ifdefs in the code so another probably won't hurt.  Glad to hear this problem exists only because it's a low priority and not because there's a fundamental obstacle.

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[Fedor Indutny]

Yeah, the compatibility is a problem as usual.

It sounds very interesting to explore it behind the v1.x, maybe I'll work on it if someone will create an issue on github and cc me ;)

Thank you for asking this!

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[Curtis Yarvin]

Issue posted, https://github.com/libuv/libuv/issues/387.  Thanks!