[Nepomuk] Review Request 109078: Add a base class for the file watcher back-ends

[Vishesh Handa]

On Fri, Feb 22, 2013 at 11:47 PM, Simeon Bird <bladud at gmail.com> wrote:

> Hi Gabriel,
>
> On 22 February 2013 08:55, Gabriel Poesia <gabriel.poesia at gmail.com>wrote:
>
>> - fanotify is completely silent regarding moves and deletes - it gives no
>> clue something happened. It doesn't catch any other event related to the
>> directories involved (file unlink, for example). Thus, it would need
>> KDirNotify as a complement, which yes, only reports things done via kio.
>>
>
> None at all? Not even a directory open? If using, eg, dolphin or other
> kio, will the directory reliably get opened (for listing) before a move
> takes place?
>
>  - The fanotify_init man page confirms that you need root privileges
>> (specifically, the CAP_SYS_ADMIN capability), and says that this constraint
>> might be relaxed in the future. But, at least currently, yes, we'd need a
>> root daemon even to watch $HOME.
>> - I couldn't get the "directed" mode to work. This is the mode in which
>> you would presumably only receive events from the directories you mark. It
>> should just be a matter of changing a couple of parameters in
>> fanotify_mark, but I didn't get it to work. If it really doesn't work,
>> we'll need to manually filter global events (as I get here about 30 "open"
>> events for /etc/passwd per second, for example).
>>
>
> Ouch. Does filtering on event type work? ie, can you listen to just
> CLOSE_WRITE events? Also, is it not working, or is it just not working
> recursively?
>
> I can see instances where a kDirWatch backend might work, if it can
> perform better than 1 million inotify watches - but I can't see it as a
> default, because a careless mv or rm would cause problems.
>

Lets use the correct terminology - It's KDirNotify. KDirWatch is KDE's
abstraction over inotify, dnotify, fam and others. We do not care about it
cause it doesn't support move events.

KDirNotify is the dbus notification api which we care about.

----

Since fanotify requires root access, it really doesn't seem like a viable
option.

How about we just stick with just inotify or inotify + kdirwatch? I know a
stray move might remove stuff, but it does have significant advantages as
well.


> Simeon
>



-- 
Vishesh Handa
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