Another look at bzr network traffic

[John Arbash Meinel]

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Andrew Cowie wrote:
> On Sun, 2010-04-04 at 12:06 -0500, John Arbash Meinel wrote:
> http://article.gmane.org/gmane.comp.version-control.bazaar-ng.general/67118
> 
> So I was about to reply to that message, but we've got this thread here,
> so here we are.
> 
> On Thu, 2010-03-18 at 08:51 -0500, John Arbash Meinel wrote: 
>> I was sort of staying out of this as a 'known bug' of the 2a format, but
>> since it wasn't clear in Andrew's head, I'll explain.
>> ...
> 
>> What that means for the current smart protocol, is that all fetches will
>> copy at least 1 fulltext, regardless of the delta size. So a 1 byte
>> change to a 1MB file will transmit 1MB of data, though after
>> autopack/pack it will probably get stored as a small handful of bytes
>> again. (While it is in its own pack, it is still stored as 1MB on disk.)
> 
> Once upon a time when people were optimizing normal operations over
> http:// it was mentioned that Bazaar is very good about using HTTP Range
> requests to only grab the actual bytes that it cares about. All good.
> 
> But this makes it sound like over the bzr{,+ssh}:// protocol that
> requesting a small revision may end up shipping an entire pack file no
> matter what. If true, then the obvious concern is "I just got repacked
> into a single pack that's now 100 MB big, goodie! here it comes!"

Not an entire pack file. An entire group-compress block, which is a much
lower level thing. It will likely send the entire fulltext of a file.

John
=:->
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