Cleaning of $XDG_CACHE_HOME and $XDG_CACHE_HOME/thumbnails

[Egmont Koblinger]

Hi guys,

On Wed, Feb 26, 2020 at 10:54 PM Bollinger, John C
<John.Bollinger at stjude.org> wrote:

> > Is it OK to clean $XDG_CACHE_HOME after a fixed time period by default?
>
> No, it is not, as a matter of policy and of the nature of $XDG_CACHE_HOME.  It is not safe or reasonable to assume that all of the contents are similar to thumbnail or browser caches, that go stale over time and that can easily and cheaply be repopulated.  What's more, those particular items are already accounted for.  The default should be to protect users' data, including cache data, about which the system has no specific knowledge or instructions.

I'm absolutely on John's side here.

Let's take ccache for example. It's a weird example because they don't
use XDG_CACHE_HOME, but they could :). I might compile a project, play
with it, get some result out of it, and think that I won't ever need
to work on it again, thus remove the git checkout tree. Then months
later something pops up and I need to check the project again. Having
the compilation cache still available might very easily save me in the
order of minutes or tens of minutes.

_My time_ is the most precious bottleneck, not the disk space or CPU
time or whatever technical. Automatic purging (based on no more
information than the timestamp of files) has much more chance to harm
than to help me.

> Overall, the assertion that the cache directory should be subject to cleaning by default seems to be a solution without a problem.

I don't think it's even a solution to that non-problem. Because if I'm
running short on disk space, I need to take immediate action purging
some files, I cannot wait for the automatic cleaning to kick in who
knows when, in days or weeks, to hopefully free up enough space (which
it most likely won't, by the way).


cheers,
egmont