Re: [qooxdoo-devel] Generator changes - /tmp may not be a good choice on *ix systems

[Gene A. <ge...@pc...>]

I have a question related to the clearing of any old temp files - does
the Qooxdoo build system update the time-date stamp of the cache files
on each run?  If so, frequent build runs would prevent any automatic
cache cleanup that only removes old files from removing the Qooxdoo
cache files.  If not, maybe that would be a smart thing to change in the
Qooxdoo build system.

  Gene

On Sun, 2009-05-31 at 23:24 +0200, Fritz Zaucker wrote:

> Hi Thomas
> 
> On Sat, 30 May 2009, thron7 wrote:
> 
> >> Most Linux distributions either clear out /tmp each time the computer
> >> boots, or mount /tmp on a virtual file system (e.g. tmpfs) that is
> >> recreated on each boot. I believe this means that on a laptop that is
> >> rebooted a few times each day, an application in development would
> >> require a complete rebuild following each boot -- a very long process, of
> >> course, with any substantial application.
> >
> > Mh, I was not aware of that. I have been working with Linux the past 10
> > years and never had my /tmp been cleared automatically.
> 
> In general, the /tmp directory on most Unix systems (including Linux) should
> be cleared at reboot. I am surprised to hear that there are systems that
> don't do that.
> 
> Of course, this isn't something that is done magically. Usually there is a
> script in /etc/init.d/ doing that. On Ubunty Jaunty (which happens to run on
> my laptop) it is the script mountall-bootclean.sh
> 
> > But then, I'm not using one of those modern desktop versions of Linux. And
> > actually, since 2 years I hardly reboot, I only hibernate. - But of
> > course, I'm interested in other people's experiences.
> 
> Even if a reboot does occur only rarely (Unix servers often aren't rebooted
> for months if not years, as a reboot is required only rarely compared to
> other OSes), the cache data might still be wanted to survive (and I don't
> really see a reason why they shouldn't).
> 
> In some sense I even think it is a mistake to not clean the tmpdir ... and a
> well maintained system might actually clean the /tmp regularly once it
> starts filling up (although a well designed algorithm will only delete old
> files and not the recently modified Qooxdoo cache).
> 
> >> I would suggest using a different environment variable variable name,
> >> e.g. QOOXDOO_CACHE_DIR, with a fallback to TMPDIR.
> >
> > I'm not sure I completely understand you here. For one thing, we are not
> > evaluating environment variables. Technically, we use the gettempdir()
> > function of one of Python's standard modules, tempfile. This in turn does
> > evaluate environment variables, but also applies a lot of platform logic,
> > so we don't have to worry about it. Since we are running
> 
> This seems reasonable for getting the "local" location for temporary files.
> And according to the documentation the first place gettempdir() tries IS the
> TMPDIR environment variable.
> 
> On the other hand, as Derrell points out, it might not be the ideal location
> IF the data in this directory is supposed to survive a reboot.
> 
> > But more importantly, the TMPDIR *is* the fallback already. Just set your
> > CACHE macro to some other path and you're set. If you don't like the
> > TMPDIR location, just override it. Config macros are our way of tailoring
> > the system, and I wouldn't want to add another mechanism, like environment
> > variables, without compelling need. - If you are running multiple
> > applications on your machine, and want to maintain a central setting, just
> > create some "site.json" and include it in the individual config.json's.
> 
> It seems to make sense to me to configure the cache location in the
> config.json file on a per application basis. This way each developer can
> decide what he wants to do.
> 
> Personally, I think it would make sense to have the cache directory default
> to a directory inside the application tree.
> 
> > But sure enough, while this should help you individually, the fallback
> > setting should be sensible for most people, so if a lot of people have the
> > issues you describe we should re-consider the default.
> 
> Perhaps /var/tmp/ would be more reasonable, although I am not sure if there
> aren't distributions that clear this as well (Ubuntu Jaunty doesn't).
> >
> >> If QOOXDOO_CACHE_DIR is not found in the environment, a warning should be
> >> issued (but not in -q "quiet" mode) because falling back to TMPDIR will
> >> cause the problem described above on each boot, causing a poor user
> >> experience of long build times. Maybe a suggestion of how to add it to
> >> .profile could be provided.
> >
> > As I said, the solution is as close as your config.json. As for the poor
> > user experience due to automatically erased /tmp directories, I would be
> > interested to learn who else has this issue?!
> 
> Just tried my current application with
> 
> ./generate source
> 
> With cache: 	 1.592u 0.112s 0:01.76 96.5%    0+0k 1944+0io 0pf+0w
> Without cache:  56.003u 0.956s 1:08.43 83.2%    0+0k 48432+0io 0pf+0w
> 
> So this WILL hurt, if the cache is deleted unintentionally.
> 
> Cheers,
> Fritz
>