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Re: Compressed Pristines (Design Doc)

From: Daniel Shahaf <danielsh_at_elego.de>
Date: Thu, 22 Mar 2012 17:43:16 +0200

Ashod Nakashian wrote on Thu, Mar 22, 2012 at 08:18:40 -0700:
> >________________________________
> > From: Daniel Shahaf <danielsh_at_elego.de>
> >To: Ashod Nakashian <ashodnakashian_at_yahoo.com>
> >Cc: "dev_at_subversion.apache.org" <dev_at_subversion.apache.org>
> >Sent: Thursday, March 22, 2012 7:30 AM
> >Subject: Re: Compressed Pristines (Design Doc)
> >
> >OK, I've had a cruise through now.
> >
> >First of all I have to say it's an order of magnitude larger than what
> >I'd imagined it would be.† That makes the "move it elsewhere" idea I'd
> >had less practical than I'd predicted.† I'm also not intending to take
> >you up on your offer to proxy me to the doc, though thanks for making it.
>
> If there are any ideas for simplifying things, I think it's well worth
> the effort. I for one am not for unecessary complexity. This is why
> I took the time to outline a set of requirements. If the requirements
> are excessive, let's simply them first. And based on the requirements
> alone can one justify the design.
>

Fair enough.

One requirement is extensibility (features in 1.9 timeframe, assuming
your design is released in 1.8). I see you included a format number,
but --- for example --- perhaps the index entries should contain a few
RESERVED bytes too? (It would have help a lot in manually fixing FSFS
corruptions if we'd left a few unused bytes here and there in revision
files...)

Another requirement is concurrency. ra_serf downloads files
concurrently, and the editor (svn_delta_editor_t, 1.8's svn_editor_t)
allows retrieving the text of multiple files concurrently. Does your
design allow for adding two new pristines with their contents arriving
interleaved? (There is one thread in the client process, but several
TCP sockets.)

> >
> >Design-wise I'm a bit surprised that the choice ended up being rolling
> >a custom file format.
>
> Personally I know not of any library that can deliver the requirements
> that we need (outlined in the doc). Again, if the requirements are in

I'm not familiar offhand with such a library either, but perhaps someone
else on list is.

> question, let's simplify them. If there is such a library, suggesting
> it will save us a lot of time and effort. Otherwise, using a Tar-like
> container will just not cut it. On the other hand, the proposed custom
> format is rather simple and its code shouldn't be complex. In fact,
> I suspect Tar is more complex (considering it must store more
> information than we do).
>

Let's see how far we can get with the custom format. If the "someone
invented that wheel already" factor pops up too often I'm sure we'll
notice.

Cheers,

Daniel

>
> -Ash
>
> >
> >Thanks for your work.
> >
> >Cheers,
> >
> >Daniel
> >
> >Ashod Nakashian wrote on Thu, Mar 22, 2012 at 00:15:21 -0700:
> >> >________________________________
> >> > From: Daniel Shahaf <danielsh_at_elego.de>
> >> >To: Greg Stein <gstein_at_gmail.com>
> >> >Cc: Ashod Nakashian <ashodnakashian_at_yahoo.com>; dev_at_subversion.apache.org
> >> >Sent: Wednesday, March 21, 2012 2:08 PM
> >> >Subject: Re: Compressed Pristines (Design Doc)
> >> >
> >> >Greg Stein wrote on Wed, Mar 21, 2012 at 16:51:47 -0400:
> >> >> On Wed, Mar 21, 2012 at 16:11, Daniel Shahaf <d.s_at_daniel.shahaf.name> wrote:
> >> >> > Ashod Nakashian wrote on Wed, Mar 21, 2012 at 12:19:02 -0700:
> >> >> >> All,
> >> >> >>
> >> >> >> I'm happy to share[1] with you the design document for the Compressed Pristines feature. The document is public and anyone can comment on any part
> >> >> >
> >> >> > I can't. †Can you please move the document to our wiki, or dump it in an
> >> >> > email to dev@, or on a pastebin, somewhere everyone canread it.
> >> >>
> >> >> I just opened it in an incognito window in Chrome. You should be able
> >> >> to access the thing.
> >> >>
> >> >
> >> >Tried, I get as far as the doc title.† I don't see its contents.
> >>
> >>
> >> Daniel (and all who can't access the doc),
> >>
> >> I'm attaching the PDF and ODT versions with updates based on Greg's comments. I'd like to hear all opinions and comments. Google docs is a fairly ideal environment for live commenting and editing, so it's too bad that you can't access the file.
> >>
> >> Please let me know if you have any notes/comments on the design. If you'd like to use the ODT file for comments and edits, please mark your input clearly and I'll update the Google doc with your notes.
> >>
> >> Thanks,
> >> Ash
> >
> >
> >
> >
> >
> >
Received on 2012-03-22 16:43:58 CET

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