[arch-general] Question about repository updates and atomicity

[Allan McRae]

On 15/08/13 17:08, Johannes Ernst wrote:
> I'm trying to understand what may and may not go wrong between package
> uploads to a repository, repository synchronization via rsync (which seems
> to be the preferred method for mirrors to get their stuff) and downloads
> via pacman.
> 
> Assume a developer uploads a new version of two packages to a repository.
> My understanding is that uploads delete the older version of the uploaded
> package currently in the repository. (unlike other package management
> systems e.g. debian's where multiple versions of the same package can
> reside in the same repository).
> 
> An hour later, a mirror repository starts rsycing. While the rsync is
> ongoing, a user uses pacman to download both packages from the mirror.
> 
> Question: what mechanisms exists, if any, to avoid that the user gets the
> old version of package A and the new version of package B? (assume the
> rsync is still ongoing while the download occurs)

The database file will either have both new packages or no new packages.


> It seems the "safe" way of doing the rsync would be to take down the mirror
> during the critical section (when all old versions are removed and the new
> ones put there instead), and restart it afterwards? Or is there something
> somewhere that I'm not seeing? The debian guys probably keep the old
> version(s) around for exactly that reason...
> 
> Any insight very much appreciated ...