[PLUG] Anyone know of "lossy" version-control software?

[William A Morita]

Wil

Perhaps you should not be using subversion or cvs for the task.
Maybe something more like dervish with code added to delete older revisions.



- Bill Morita
wamorita At hevanet.com

-----Original Message-----
From: plug-bounces at lists.pdxlinux.org
[mailto:plug-bounces at lists.pdxlinux.org] On Behalf Of wcooley at nakedape.cc
Sent: Saturday, December 19, 2009 7:35 PM
To: plug at lists.pdxlinux.org
Subject: [PLUG] Anyone know of "lossy" version-control software?

I am looking for something that, as far as I have been able to find, does
not exist. I want a version-control package that intentionally and
programmatically destroys revisions.

Before I explain further, let me provide some background use-cases. We
maintain a lot of data automatically and usually do a plain-text dump for
back up and in some cases we stuff these dumps into Subversion, primarily
for ease of roll-back in case something should break. For example, we have
LDIF dumps of our LDAP tree; text dumps of our Cyrus IMAP mailbox list;
generated /etc/group files that are stored and distributed via Subversion,
etc. At other times, when I was subject to Windows DNS admins, I stored
periodic snapshots of DNS zones with RCS.

The problem with keeping this data in a traditional VCS like Subversion is
that I don't actually need all of those revisions. I really need hourly
dumps for the last few days for roll-back purposes. It is sometimes nice to
have a daily or weekly dump to use for data-mining purposes, to answer
questions like, "When did we start setting this attribute like this?" or "At
what rate has our mailbox list grown?" Having snapshots every 5 minutes for
a couple hours wouldn't be bad either, but it's not really feasible if they
exist forever. If you think of the way rrdtool maintains numerical
time-series data, then the idea should seem pretty familiar.

So what I want is some sort of archival or version-control software that can
be configured for the programmed destruction of old versions and keeping
selected samples. Back-up software sort of does this and many packages will
backup to a file, but it seems like overkill to have to setup and configure
Bacula or Amanda just to manage a handful of files.

Part of the problem is that I just don't know what to call something like
this. "Round-robin archive" sounds good, but that's what rrdtool calls its
archive files. "Rolling-archive" also sounds right, but from what I can tell
that's a feature of the K2 WordPress UI theme. "Lossy VCS" or "lossy SCM"
leads only to snide comments about VisualSourceSafe.

I have used CVS and Subversion enough to know that getting them to throw
away revisions is painful. I've been using Git a lot lately and it likewise
seems unwilling to get rid of stuff. There are a lot of other ones, like
Arch, Darcs, Bazaar, Mercurial, etc., that I know little to nothing of, but
what I am asking for is something they are fundamentally designed to not do.
I've been wondering about something built on top of the Git plumbing-layer,
but do not have enough of a grasp of it to know if it is possible.

Any ideas?

Wil

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