[pacman-dev] Repository management

[Dave Reisner]

On Tue, May 09, 2017 at 10:54:44PM +1000, Allan McRae wrote:
> Hi all,
> 
> Every time I attempt to work on repo-add, I find it to be a very
> difficult endeavour.  Even though it is half the size of makepkg
> (without even including any of libmakepkg), it is much more convoluted
> to work on.
> 
> We also have a weird repository database system.  We have:
> - .db dbs with package information, signatures and delta information
> - .files dbs that are the same as .db dbs but additionally include filelists
> 
> There are two reasons the .files dbs replicate all information in the
> .db dbs
>  - .db and .files dbs getting out of sync could cause issues
>  - a complete database is useful for things like archweb, mostly to
> avoid the above
> 
> I would also like to include information on source packages to these
> databases.  The files information is separate due to wanting our primary
> database to be small.  Likewise, source package information needs to be
> separate (the signatures take most of the size in the .db dbs, so adding
> source package signatures effectively doubles the size).
> 
> So two points up for discussion:
> 
> 
> 1) Sync repository layout?  I don't see any point in leaving the tar
> based format, as reading of sync databases is not a bottleneck.  (The
> local db format can be a bottleneck, but that is a separate discussion...)

Isn't this a historical reversal? IIRC, the sync DBs used to be expanded
onto disk, and we decided to leave them as tarballs to address
performance/fragmentation concerns.

> Do we split the information in .db out of .files and add a .full db with
> complete information?  Then any .src db could follow suit and just have
> source package information.  How do we get around the out of sync issue
> (e.g., a package is removed from .db, but we have an old .files database
> with it).  Do we add timestamps, and print a warning on -F operations
> when the two are out of sync?
> 
> 
> 2) Do we need a better (read "more easily maintainable") tool for
> handling database generation and updates?  libalpm already can read in
> information package files, so we could add libalpm/db_write.c with the
> database creation functions.   Should we unify our repo format with our
> local database format which we already write?
> 

I'd urge you not to make this a part of pacman. It's too far off the
beaten path for most users to make it a part of an already complicated
tool.

> 
> I am looking for ideas here.  Please brainstorm to your hearts content.

WRT replacing repo-add, I'd suggest we come up with a the use cases we
want to support, design an interface to meet them, and then come up with
the implementation. Might be nice to start with the Arch Linux
repository layout as an example that we'd want to support (pooled
packages with symlinks into repo dirs).

> Cheers,
> Allan