Re: [gentoo-dev] Re: emerge-webrsync bandwidth improvement

[Brian Harring <ferringb@gentoo.org>]

On Mon, May 09, 2005 at 09:09:57AM +0200, sf wrote:
> Brian Harring wrote:
> ...
> > B) Permenant solution needed for when snapshots upstream aren't 
> >    generated, as occured 04/29.  This probably will have to be 
> >    serverside- easiest route, otherwise have to implement version 
> >    jumping logic in bash, which is ugly
> 
> Generate an empty delta when no snapshot exists?
Doesn't really work that way; each patch basically is a list of 
commands, multiple patches == pulling bits/pieces of commands from 
the the referencing version for that patch.
Basically it's overlaying commands; an empty patch would break the 
chain.  While it doesn't sound perfect/pretty, generating a patch that 
is just a copy of the reference (the command list is just a copy of 
all of the reference file to the versioned file).  It's actually 
easier/cleaner to go this route, then modify the client- the client's 
approach is simply, I get patch from day N-1 to N, wash rinse repeat.  

Modifying it to handle arbitrary jumps basically means the client has 
to inspect the remote server for what's available, rather then 
just making an attempt for a fetch.  It's easiest, and is only around 
60 bytes per day upstream snapshots go out... so it's minor overhead, 
and shouldn't occur all that often :)

> > C) cleansing of old snapshots.  Current 'handling' of it (read: not 
> >    doing a damn thing) is ugly.  :)
> 
> Always create the most recent snapshot and delete old snapshots and all
> deltas?
Pretty much.  Pushed emerge-delta-webrsync-2 into the tree last 
friday, should address all of the issues I mentioned.
~brian
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