[Dirvish] A suggestion for dirvish-expire

Dave Howorth dhoworth at mrc-lmb.cam.ac.uk
Wed Dec 5 10:00:39 UTC 2012


Hernán J. González wrote:
> This works, and might seem ingenious. Actually, it's terribly fragile,
> it's a nightmare to maintain - or a bomb waiting to explode
> Suppose someday you want to change your backup schedule, and you start
> running dirvish on Sunday-Tuesday-Thrusday. You're doomed. You can't do it.
> And if you do it and naively change the '5' (week day) in
> your expire-rules to '4' ... ooops... you've lost all your old backups.
> (And if you don't change them, the new backups will expire after 10 days)

Either you or I misunderstands how expiry works. I think dirvish
calculates the expiry date when it creates each backup and stores it in
the summary file. dirvish-expire just checks that date, so changing the
day on which you run dirvish makes absolutely no difference to backups
that already exist.

> Another useful (orthogonal) option to dirvish-expire would be to
> look for some special file inside the vault that works as a "dont ever
> expire me" flag.

It already exists. If you change the expiry date in the summary file to
a century in the future, that's what it will do.

As Ken says, though, if you write a useful new expiry program that
behaves as you wish then people will use it. There's no need to change
the behaviour of the existing programs (i.e. 'break' them)

Cheers, Dave


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