Cleaning of $XDG_CACHE_HOME and $XDG_CACHE_HOME/thumbnails

[Bollinger, John C]

On Wednesday, February 26, 2020 8:51 AM, Benjamin Berg wrote:

> [...] I *do* want applications to explicitly ship an opt-out file if they do not want any cleaning ever. And threatening with automatic clean-up is probably a good idea, because otherwise no one will bother.

This is simply wrongheaded.  Applications should not be required to opt-out, period, and it is reasonable for them to rely on not having to opt out.  It is moreover absolutely unacceptable to threaten people in order to obtain compliance with an arbitrary policy, as you propose to do.  It would be fine to provide a facility for explicit opt-out, and some applications might make use of it for extra assurance.  It is probably right that most will not bother, but that should not be regarded as a problem.

> So, I would still propose to write the requirement to ship a configuration file and the possibility of defaulting to clean after e.g. 30 days into the specification.

On the contrary.  If this generalized facility is implemented then it should provide a clear promise that only cache contents explicitly configured for automatic cleanup will be affected, with the possible pseudo-exception that areas that are already subject to such cleanup (e.g. thumbnails) will continue to be cleaned up by default.  I would expect the "by default" part of that to take the form of opt-in configuration being shipped and installed by default, presumably in $XDG_CONFIG_DIR, as opposed to the behavior being built directly into the software.

> That does not say anything about how long the grace period for such a change would be. And while I personally think we should flip the default eventually, we could still decide to never actually do so. Or leave the decision up to distributions and administrators.

If it makes you feel any better, you can make the promise that opt-in is required a weak one, so that you can imagine that it would be on the table to flip the policy at some point in the future.  In reality, however, I don't see any reason to think that it would ever be reasonable to require opt-out under any circumstances.


John Bollinger


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