Re: [Gnu-arch-users] Re: libraries don't play well with partial mirrors

[Aaron Bentley]

Jason McCarty wrote:
> Aaron Bentley wrote:
>
> > That's another argument for local caches instead of local mirrors;
>
>
> Maybe, but in this case I would want most of the changesets to be
> locally cached, as well as a few full revisions. Sounds a lot like a
> partial mirror+revlib to me.

No, cache+revlib would be much better.

The differences between a mirror and a cache are
1. if data is not in a cache, that's a cache miss, not a corrupt mirror.
2. a well-designed cache will never return outdated data
3. partial mirrors contain entire versions, while caches can contain 
parts of specific revisions
4. caches can be used in such a way that they will not download 
unnecessary data

The differences between a cache and a greedy are
1. archive-format storage takes much less space per revision
2. archive-format storage cannot be used as a reference tree
3. caches often have a fixed maximum size

> > Well, if you have a library revision for tla--devo--1.2--patch-114, you 
> > can't determine whether that's an ancestor of tla--devo--1.3--patch-2 
> > without consulting the revision data for all intermediate revisions.
>
>
> But if my mirror doesn't contain the 1.2 branch, I don't expect my
> revlib to either.

Why not?  Maybe that's true for your case, but it's not necessarily true 
in every case.  I can well imagine that I might mirror Tom's archive, 
but I still have revlibs for 1.2.

> > It would sure help the backbuilder if stuff like this didn't cause 
> > immediate program termination.  The backbuilder doesn't need every 
> > arch_archive_connect to succeed, but arch_archive_connect will panic if 
> > it fails.
>
>
> Sounds reasonable. Is my bug one of those failures which are easily
> recoverable?

With the current code, it could be done by checking for missing 
revisions before determining their type.  This would cause the archive 
scan to take twice as long.  Or else we could change the interface of 
arch_revision_type() so it can indicate a missing revision.

Any fixes to the current code will be obsolete when the backbuilder's 
integrated.  It currently doesn't tolerate missing revisions.

Aaron

--
Aaron Bentley
Director of Technology
Panometrics, Inc.