[Nepomuk] Review Request 106748: FileWatch: Use KAuth to automatically raise the inotify watch limit if we run out of watches.

[Simeon Bird]

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http://git.reviewboard.kde.org/r/106748/
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(Updated May 4, 2013, 2:48 a.m.)


Review request for Nepomuk, Sebastian Trueg and Vishesh Handa.


Changes
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Fixed issues


Summary (updated)
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FileWatch: Use KAuth to automatically raise the inotify watch limit if we run out of watches.


Description (updated)
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FileWatch: Use KAuth to automatically raise the inotify watch limit if we run out of watches.

When we run out of watches, use a KAuth action to double the inotify
watch limit (by writing to /proc/sys/fs/inotify/max_user_watches).
At the same time, make the new setting persist across reboots by writing
/etc/sysctl.d/97-kde-nepomuk-filewatch-inotify.conf.

If for some reason raising the limit does not work, print a message to
syslog.

While the limit is being raised, no new watches will be added, only
queued.

==Potential issues==

1. At the moment there is no way to turn this off, except by not using nepomuk or denying the user the requisite kauth permissions. This is the sort of thing that people complain about, but I can't really see any reason to want to do that - you'd be running nepomuk in a "known broken" configuration, which makes no sense.

2. the action description string is "To avoid missing file changes, raise the folder watch limit", which could probably be improved.

3. The method of making the change persist across reboots is to write a file to /etc/sysctl.d, which is a bit anti-social. (note that if /etc is not writable, it simply does nothing). /etc/sysctl.d should work on all systemd distros, debian (including derivatives such as ubuntu) and gentoo.

Part of me wants to make this a separate action, but as I understand it this would require a second prompt and a second authorization, which would be a bit annoying. Also, the user's file system isn't going away - if they wanted a larger limit once, they almost certainly want it again, so there are limited reasons for not wanting it permanent. But finer grained permissions are a Good Thing, so I'm not so sure about this.

4. If the user has manually set the watch limit to a too-low number in sysctl.conf, it could potentially over-ride the file in /etc/sysctl.d, leading to the prompt appearing on every boot.

Also, I'd just like to mention that I was quite impressed at how easy to KAuth was to work with.


Diffs (updated)
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  cleaner/CMakeLists.txt 87bae29f4dfa8eb9c1d5c0414e4661d7d461b726 
  cleaner/cleaningjob.h eb0548b06daaf07dc7ba4b2ede6fc0b3bc65acdb 
  cleaner/nepomukcleaner.desktop 35136a0b50f4419dfc40c3c5bfa65e23887fd368 
  cleaner/nepomukcleaningjob.desktop 6ebb1c96c5abb09c7d0048768729ab4252cde579 
  libnepomukcore/service/nepomukservice2.desktop 0361017fdb519b2881d1be8151026bfbab917d88 
  services/fileindexer/indexer/extractorplugin.h 8e264941bfa40ca6ac7d546740c9d6cea84f77ab 
  services/fileindexer/indexer/nepomukexiv2extractor.desktop aea0ec8b496c96eb853aa0426cc72a14b4eb505c 
  services/fileindexer/indexer/nepomukextractor.desktop 8e8da0cc3b08b33bd2962b4dcd92207ac717d688 
  services/fileindexer/indexer/nepomukffmpegextractor.desktop b7b21a65e30a1df9bd6ab4d849ab609313e5d33c 
  services/fileindexer/indexer/nepomukplaintextextractor.desktop 9653070e96e85d6a1b4def1f421e1a7d05ea61e0 
  services/fileindexer/indexer/nepomukpopplerextractor.desktop 25aa375e72bbf9777d4d74728af853571d31f90e 
  services/fileindexer/indexer/nepomuktaglibextractor.desktop f5ca96b784d73fdebfda11762f0cd35280e90b70 
  services/fileindexer/indexer/test/CMakeLists.txt 6422c895484a30722e882ecdb65beca917bf46df 
  services/filewatch/CMakeLists.txt 338fe8c2b008b1c898d71934e4de3028c0078fca 
  services/filewatch/kinotify.h e795371d922d483bce29e9eea03c1eeb97738355 
  services/filewatch/kinotify.cpp 94babfe437ddfa8c9318b8b29dd8c8a03a4e71b1 
  services/filewatch/nepomukfilewatch.h 66e0112d909a2abefed48d0959323e7f32a5ff9b 
  services/filewatch/nepomukfilewatch.cpp fbbf3db619516e296bc1e4aa07f53808fbe4a4c0 
  services/filewatch/nepomukfilewatch.desktop a0710e3fd399123b23012faec25a5a687ca9eacb 
  services/filewatch/org.kde.nepomuk.filewatch.actions PRE-CREATION 
  services/filewatch/raiselimit.h PRE-CREATION 
  services/filewatch/raiselimit.cpp PRE-CREATION 

Diff: http://git.reviewboard.kde.org/r/106748/diff/


Testing (updated)
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Compiled, ran, raised and lowered the limit a few times.


Thanks,

Simeon Bird

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