F26 Self Contained Change: Fontconfig cache directory change

[Jan Kurik]

= Proposed Self Contained Change: Fontconfig cache directory change =
https://fedoraproject.org/wiki/Changes/FontconfigCacheDirChange

Change owner(s):
* Akira TAGOH <tagoh AT redhat DOT com>

The fontconfig cache files are placed onto /var/cache/fontconfig now.
this seems incompatible with the ostree model. so this is a proposal
to move it to /usr/lib/fontconfig/cache.



== Detailed Description ==
The fontconfig cache files are placed onto /var/cache/fontconfig now.
this seems incompatible with the ostree model. so this is a proposal
to move it to /usr/lib/fontconfig/cache as proposed at #1377367 [
https://bugzilla.redhat.com/show_bug.cgi?id=1377367 ]



== Scope ==
* Proposal owners: Rebuild the fontconfig package with the changes of
the proposed cache directory.

* Other developers: N/A (not a System Wide Change)

* Release engineering: N/A (not a System Wide Change)

* List of deliverables: N/A (not a System Wide Change)

* Policies and guidelines: N/A (not a System Wide Change)

* Trademark approval: N/A (not needed for this Change)
-- 
Jan Kuřík
Platform & Fedora Program Manager
Red Hat Czech s.r.o., Purkynova 99/71, 612 45 Brno, Czech Republic

[Ralf Corsepius]

On 12/21/2016 09:22 AM, Jan Kurik wrote:
>  = Proposed Self Contained Change: Fontconfig cache directory change
> =
>  https://fedoraproject.org/wiki/Changes/FontconfigCacheDirChange
>
>  Change owner(s):
>  * Akira TAGOH <tagoh AT redhat DOT com>
>
>  The fontconfig cache files are placed onto /var/cache/fontconfig now.
>  this seems incompatible with the ostree model. so this is a proposal
>  to move it to /usr/lib/fontconfig/cache. 
This proposal likely is incompatible to the FHS.

Files in directories below /usr/lib are supposed to static and not to be 
dynamically created.

[Randy Barlow]

On Wed, 2016-12-21 at 09:42 +0100, Ralf Corsepius wrote:
>  > The fontconfig cache files are placed onto
> /var/cache/fontconfig
>  > now.
>  > this seems incompatible with the ostree model. so this is a
>  > proposal
>  > to move it to /usr/lib/fontconfig/cache.
>  
>  This proposal likely is incompatible to the FHS.
>  
>  Files in directories below /usr/lib are supposed to static and not to
>  be 
>  dynamically created. 
I agree - let's not violate FHS.

[Matthew Miller]

On Wed, Dec 21, 2016 at 11:18:54AM -0500, Randy Barlow wrote:
>  > > to move it to /usr/lib/fontconfig/cache.
>  > This proposal likely is incompatible to the FHS.
>  > 
>  > Files in directories below /usr/lib are supposed to static and not
>  > to be  dynamically created.
>  I agree - let's not violate FHS. 
Keeping to standards where they make sense is valuable. In this case, I
want it to be clear that this isn't just a "doesn't meet red tape!
denied!" stamp — the desire is to avoid runtime-generated files under
/usr, right?

When I look at the details, this seems like an edge case. See the
linked bug (https://bugzilla.redhat.com/show_bug.cgi?id=1377367). This
isn't really _runtime_ variable content. It's generated at
package install time. The FHS says:

   /var is specified here in order to make it possible to mount /usr
   read-only. Everything that once went into /usr that is written to
   during system operation (as opposed to installation and software
   maintenance) must be in /var.

... and the thing is, this particular cache is generated during
"installation and software maintenance".

I see that the fc-cache data is arch-specific, but is it really
host-specific? What if we just pre-generated it at *build* time and put
it into /usr/share or /usr/lib? I guess that'd end up making font files
archful, but that's not the worst thing.

Hmmm, I see that the arch-specific part is encoded in the filename
(like d3379abda271c4acd2ad0c01f565d0b0-le64.cache-7). None of this
stuff is very big; only a few k per font. What if we just included all
of the arch-specific files in every font package?

Bonus: less stuff run in %post scripts!

-- 
Matthew Miller
<mattdm(a)fedoraproject.org&gt;
Fedora Project Leader

[Vít Ondruch]

Dne 21.12.2016 v 18:08 Matthew Miller napsal(a):
>  On Wed, Dec 21, 2016 at 11:18:54AM -0500, Randy Barlow wrote:
> >>> to move it to /usr/lib/fontconfig/cache.
> >> This proposal likely is incompatible to the FHS.
> >>
> >> Files in directories below /usr/lib are supposed to static and not
> >> to be  dynamically created.
> > I agree - let's not violate FHS.
>  Keeping to standards where they make sense is valuable. In this case, I
>  want it to be clear that this isn't just a "doesn't meet red tape!
>  denied!" stamp — the desire is to avoid runtime-generated files under
>  /usr, right? 
While you are afraid, I see in the bugzilla a lot of "it was done
previously, we can do it again". And next time this case will be used as
a justification for moving more and more stuff into /var.

>  When I look at the details, this seems like an edge case. See the
>  linked bug (https://bugzilla.redhat.com/show_bug.cgi?id=1377367). This
>  isn't really _runtime_ variable content. It's generated at
>  package install time. The FHS says:
>
>     /var is specified here in order to make it possible to mount /usr
>     read-only. Everything that once went into /usr that is written to
>     during system operation (as opposed to installation and software
>     maintenance) must be in /var.
>
>  ... and the thing is, this particular cache is generated during
>  "installation and software maintenance".
>
>  I see that the fc-cache data is arch-specific, but is it really
>  host-specific? What if we just pre-generated it at *build* time and put
>  it into /usr/share or /usr/lib? I guess that'd end up making font files
>  archful, but that's not the worst thing. 
I live under impression (may be wrong) that it should be safe to delete
content of /var/cache on disk restricted devices ...


Vít


>  Hmmm, I see that the arch-specific part is encoded in the filename
>  (like d3379abda271c4acd2ad0c01f565d0b0-le64.cache-7). None of this
>  stuff is very big; only a few k per font. What if we just included all
>  of the arch-specific files in every font package?
>
>  Bonus: less stuff run in %post scripts!
>

[Vít Ondruch]

Dne 21.12.2016 v 18:26 Vít Ondruch napsal(a):
>  Dne 21.12.2016 v 18:08 Matthew Miller napsal(a):
> > On Wed, Dec 21, 2016 at 11:18:54AM -0500, Randy Barlow wrote:
> >>>> to move it to /usr/lib/fontconfig/cache.
> >>> This proposal likely is incompatible to the FHS.
> >>>
> >>> Files in directories below /usr/lib are supposed to static and not
> >>> to be  dynamically created.
> >> I agree - let's not violate FHS.
> > Keeping to standards where they make sense is valuable. In this case, I
> > want it to be clear that this isn't just a "doesn't meet red tape!
> > denied!" stamp — the desire is to avoid runtime-generated files under
> > /usr, right?
>  While you are afraid, I see in the bugzilla a lot of "it was done
>  previously, we can do it again". And next time this case will be used as
>  a justification for moving more and more stuff into /var. 
Of course I meant /usr ...

V.


> > When I look at the details, this seems like an edge case. See the
> > linked bug (https://bugzilla.redhat.com/show_bug.cgi?id=1377367). This
> > isn't really _runtime_ variable content. It's generated at
> > package install time. The FHS says:
> >
> >    /var is specified here in order to make it possible to mount /usr
> >    read-only. Everything that once went into /usr that is written to
> >    during system operation (as opposed to installation and software
> >    maintenance) must be in /var.
> >
> > ... and the thing is, this particular cache is generated during
> > "installation and software maintenance".
> >
> > I see that the fc-cache data is arch-specific, but is it really
> > host-specific? What if we just pre-generated it at *build* time and put
> > it into /usr/share or /usr/lib? I guess that'd end up making font files
> > archful, but that's not the worst thing.
>  I live under impression (may be wrong) that it should be safe to delete
>  content of /var/cache on disk restricted devices ...
>
>
>  Vít
>
>
> > Hmmm, I see that the arch-specific part is encoded in the filename
> > (like d3379abda271c4acd2ad0c01f565d0b0-le64.cache-7). None of this
> > stuff is very big; only a few k per font. What if we just included all
> > of the arch-specific files in every font package?
> >
> > Bonus: less stuff run in %post scripts!
> >
>  _______________________________________________
>  devel mailing list -- devel(a)lists.fedoraproject.org
>  To unsubscribe send an email to devel-leave(a)lists.fedoraproject.org

[Matthew Miller]

On Wed, Dec 21, 2016 at 06:26:48PM +0100, Vít Ondruch wrote:
>  > I see that the fc-cache data is arch-specific, but is it really
>  > host-specific? What if we just pre-generated it at *build* time and put
>  > it into /usr/share or /usr/lib? I guess that'd end up making font files
>  > archful, but that's not the worst thing.
>  
>  I live under impression (may be wrong) that it should be safe to delete
>  content of /var/cache on disk restricted devices ... 
While I haven't done it, it's my understanding that it is safe to
delete the fontconfig cache files. They're a performance optimization.

The trouble is that in Fedora, we generate them at package install
time; I don't _think_ anything else ever recreates the system cache. I
guess another option would be to move this to user sessions and rely on
~/.cache/fontconfig somehow. Maybe someone from the desktop team can
weigh in here.... I've got files in that directory on my systems, some
of them recent, and I'm not sure how they got there.

-- 
Matthew Miller
<mattdm(a)fedoraproject.org&gt;
Fedora Project Leader

[Randy Barlow]

On Wed, 2016-12-21 at 12:08 -0500, Matthew Miller wrote:
>  I see that the fc-cache data is arch-specific, but is it really
>  host-specific? What if we just pre-generated it at *build* time and
>  put
>  it into /usr/share or /usr/lib? I guess that'd end up making font
>  files
>  archful, but that's not the worst thing.
>  
>  Hmmm, I see that the arch-specific part is encoded in the filename
>  (like d3379abda271c4acd2ad0c01f565d0b0-le64.cache-7). None of this
>  stuff is very big; only a few k per font. What if we just included
>  all
>  of the arch-specific files in every font package? 
I think moving this stuff to build time does make sense if it really
isn't host specific.

[Björn Persson]

>  The fontconfig cache files are placed onto /var/cache/fontconfig
> now.
>  this seems incompatible with the ostree model. so this is a proposal
>  to move it to /usr/lib/fontconfig/cache. 
Is OStree calling for the entire /var/cache to disappear, or is there
something special about the Fontconfig cache?

If the Fontconfig cache doesn't belong in /var/cache for some reason,
then shouldn't it be /var/lib/fontconfig/cache? I don't see how a cache
could belong under /usr.

Björn Persson

[Colin Walters]

On Wed, Dec 21, 2016, at 07:19 AM, Björn Persson wrote:
>  > The fontconfig cache files are placed onto /var/cache/fontconfig
> now.
>  > this seems incompatible with the ostree model. so this is a proposal
>  > to move it to /usr/lib/fontconfig/cache.
>  
>  Is OStree calling for the entire /var/cache to disappear, or is there
>  something special about the Fontconfig cache? 
No.  I replied to this in the bug:
https://bugzilla.redhat.com/show_bug.cgi?id=1377367#c9