[Bug 1372673] Re: excessive debconf use when triggered

Fri Sep 26 09:26:34 UTC 2014

Fixed in utopic now:

man-db (2.7.0-1) unstable; urgency=medium

  * New upstream release:
    - Add systemd tmpfiles snippet to clean up old cat files after a week.
    - Run "col -b -p -x" over cat pages if possible before parsing them
      (closes: #751934).
    - Move database mtime out of the database into file metadata, making the
      database reproducible between installations (closes: #760895).
    - Use high-precision timestamps.
    - Order files by first physical extent before reading (closes: #574410).
    - Prioritise COLUMNS above TIOCGWINSZ (LP: #1315282).
    - Formatting improvements to man(1) (closes: #726266).
    - Don't use pointed-to name as title for database-located pages (closes:
      #709405).
    - Move zsoelim to /usr/lib/man-db/.
  * Remove unnecessary entries from debian/dirs.
  * Cache the value of man-db/auto-update in the file system, so that we
    don't have to talk to debconf when processing triggers (closes:
    #579075).
  * Add MIME handlers (thanks, Kevin Ryde; closes: #725157).
  * Override the long-standing Lintian warning for non-standard-dir-perm on
    /var/cache/man.
  * Adjust cron.daily to skip cat file cleanup if running under systemd,
    since the upstream-provided tmpfiles snippet now handles that.
  * Rebuild the database on upgrade to this version, since the format has
    changed.

 -- Colin Watson <cjwatson at debian.org>  Mon, 22 Sep 2014 19:43:40 +0100

** Changed in: man-db (Ubuntu)
       Status: Fix Committed => Fix Released

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https://bugs.launchpad.net/bugs/1372673

Title:
  excessive debconf use when triggered

Status in “man-db” package in Ubuntu:
  Fix Released
Status in “man-db” source package in Lucid:
  Fix Committed
Status in “man-db” source package in Precise:
  Fix Committed
Status in “man-db” source package in Trusty:
  Fix Committed
Status in “man-db” package in Debian:
  Fix Released

Bug description:
  SRU justification:

  [Impact]

  We see rather frequent hard-to-debug upgrade failures that amount to
  man-db's trigger failing in some way that has nothing to do with the
  mandb program itself, but rather in some kind of communication with
  the package management frontend.  Almost all the open bugs on Ubuntu
  man-db come down to this in one way or another.  The root cause is, I
  believe, that it is not really safe to use debconf from a dpkg
  trigger: while debconf itself behaves as if it were Essential, the
  debconf protocol is often mediated by various frontends with less
  stringent practices.  It would certainly be a good idea to get man-
  db's trigger out of the loop here, as dpkg tends to run it at the end
  of an unpack phase when large numbers of packages are unconfigured,
  which is pretty much the worst case for having this work properly.

  In the past I've tried to investigate why debconf fails in these
  situations.  I've come to believe this is a wild goose chase, and that
  the common case of ordinary postinsts sourcing the debconf confmodule
  is much less likely to be a problem due to the nature of
  unpack/configure sequencing; I admit that I don't have proof of this,
  but having one fewer script using debconf is surely not going to make
  things worse, and since lots of unpack runs pull the man-db trigger it
  seems likely to improve things substantially.

  The man-db trigger reads a single value from debconf to tell it
  whether to automatically update the manual page database (used by
  apropos and whatis).  This is in an agreed location in debconf so that
  such things as package builders can save time by suppressing the
  database update.  There is, however, no reason to read this value
  every time the trigger is activated; we can just cache it under
  /var/lib/man-db/ when man-db is configured and then do a much simpler
  file-level test in the trigger.  I should have thought of this years
  ago.

  To have the maximum benefit for upgraders, we should do what we can to
  ensure that they have a fixed version of man-db installed before the
  upgrade.  I'd therefore like to apply this fix to all currently-
  supported releases.

  [Test Case]

  I don't have a reliable reproduction scenario, but I have two
  suggestions, which are in the sort of general vein of unit testing and
  integration testing respectively:

   * Install the new version of man-db and check that it causes /var/lib/man-db/auto-update to exist if and only if the debconf value for man-db/auto-update is true, and in turn that this still causes the database to be updated or not updated respectively when installing a package containing a manual page.
   * After installing the new version of man-db, upgrade to the next supported or development series using the upgrade tool of your choice.

  [Regression Potential]

  Installing packages that contain manual pages and running system
  upgrades should exercise this pretty thoroughly.  Since in general
  this weakens the constraints on achieving successful upgrades, the
  main thing to watch out for would just be things like inverted logic
  that might cause the database not to be updated when it should be or
  vice versa.

  Original report follows, imported from Debian bug
  http://bugs.debian.org/579075:

  Package: man-db
  Version: 2.5.7-2
  Severity: wishlist

  I noticed that man-db starts debconf when triggered. Given how
  often triggers run, I think that should be optimised. Ie, move
  the $1 = triggered test above the confmodule sourcing.

  -- System Information:
  Debian Release: squeeze/sid
    APT prefers unstable
    APT policy: (500, 'unstable'), (500, 'stable')
  Architecture: i386 (i686)

  Kernel: Linux 2.6.32-3-686 (SMP w/2 CPU cores)
  Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8)
  Shell: /bin/sh linked to /bin/dash

  Versions of packages man-db depends on:
  ii  bsdmainutils            8.0.10           collection of more utilities from
  ii  debconf [debconf-2.0]   1.5.32           Debian configuration management sy
  ii  dpkg                    1.15.7.1         Debian package management system
  ii  groff-base              1.20.1-9         GNU troff text-formatting system (
  ii  libc6                   2.10.2-6         Embedded GNU C Library: Shared lib
  ii  libgdbm3                1.8.3-9          GNU dbm database routines (runtime
  ii  zlib1g                  1:1.2.3.4.dfsg-3 compression library - runtime

  man-db recommends no packages.

  Versions of packages man-db suggests:
  ii            5.0.386.0~svn20100423r45407-0u Chromium browser
  ii            2.30.2-1                       Intuitive GNOME web browser
  pn            <none>                         (no description available)
  ii            3.5.9-2                        Web browser based on Firefox
  ii            436-1                          pager program similar to more
  ii            0.5.2-4                        WWW browsable pager with excellent

  -- debconf information excluded

  --
  see shy jo

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