[Bug 1393832] Re: Modules fail to enable when configured after apache2 is configured

[Robie Basak]

I tried building 1.17.21 from Debian on Vivid, downgrading to that, and
I still get the same (different) behaviour on Vivid. So it seems that it
isn't directly a dpkg version difference, but perhaps something else
different in Ubuntu (or dpkg configuration?) that is causing this
difference in behaviour.

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Title:
  Modules fail to enable when configured after apache2 is configured

Status in “apache2” package in Ubuntu:
  New
Status in “dpkg” package in Ubuntu:
  New

Bug description:
  This is related to Debian bug 745834 and Launchpad bug 1312854, which
  Stefan kindly fixed in http://anonscm.debian.org/cgit/pkg-
  apache/apache2.git/commit/?id=804b53b7d5901e47c2751cdf78908ccd9c594c5b
  that went into 2.4.10-3 that I merged in 2.4.10-7ubuntu1 that is now
  stuck in vivid-proposed.

  The fix seems to work fine in Debian, but not in Ubuntu, though I
  haven't been able to figure out why. It seems to be a difference in
  behaviour between dpkg 1.17.21 in Debian and dpkg 1.17.21ubuntu1 in
  Ubuntu.

  The code:

      if ! dpkg-query -f '${Status}' -W apache2|grep -q installed; then

  is inside apache2-maintscript-helper, which is called from libapache2
  -mod-passenger's postinst.

  I thought this was a bit dubious as I seem to recall something about
  dpkg reentrancy within a maintainer script to be unreliable and not
  recommended, though I can't find any reference to that right now.

  I can reproduce this on Ubuntu (with vivid-proposed in sources.list)
  by running "apt-get install apache2 libapache2-mod-passenger", but
  also again by running "dpkg -P apache2 libapache2-mod-passenger" and
  then (from /var/cache/apt/archives) "dpkg -i
  apache2_2.4.10-7ubuntu1_amd64.deb libapache2-mod-
  passenger_4.0.53-1_amd64.deb".

  In both these cases apache2 is configured first, and then libapache2
  -mod-passenger. However, on Ubuntu, I get the output "Package apache2
  is not configured yet. Will defer actions by package libapache2-mod-
  passenger." during configuration of libapache2-mod-passenger, even
  though apache2 was configured. As a consequence, the module never gets
  enabled as expected, and the puppet dep8 test fails.

  On Debian, I cannot reproduce this. The result of "if ! dpkg-query -f
  '${Status}' -W apache2|grep -q installed" seems to be the opposite in
  exactly the same scenario.

  So I'm not sure whether I can file this as a bug in Debian since I
  don't know whether the dpkg-query is defined to work, or in fact why
  Debian and Ubuntu behave differently on this.

  Adding a dpkg task, since it'd be nice to have a definitive answer
  (that applies to Debian too) as to whether this call is defined to
  work as expected, or if it is documented to not be permitted to be
  used.

  If we cannot do it this way, then maybe touching a file in
  apache2.postinst (and removing it in prerm or wherever) would be
  another way to test to see if apache2 is configured yet, that would
  work for us in this case.

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