RFE: Stackable namespaced repositories

I've been working on trying to package python virtual environments with rpm (outline here: http://orionlibre.blogspot.com/2015/05/deploying-scientific-python-enviro...). While this particular project is python based, the same basic concept can be applied to anything else that allows manipulating the load path - which is pretty much everything (PATH, LD_LIBRARY_PATH, PERLINC, etc). I'm most familiar with the HPC world which does this a lot - providing different versions of various packages in a hierarchy and using environment modules to allow users to load the desired stack at runtime. This is also essentially the same thing that SCLs do, though SCLs are more isolated from the base system. The big problem that this exposes in rpm packaging is "namespacing" the rpms: rpms in the "stacked" repo can depend on packages in the system repos, but not vice-versa. So we need to put them into a different namespace manually (I'm using a %{?pyvenv_name_prefix} macro, SCLs use %{scl_prefix}). Complicating this is that one needs to add the prefix to the names of other packages in the repository when specifying requirements - which may not be known ahead of time. It would be very nice if this could be handled automatically. What I think would work is if a repository could be marked as a "stacked" repository and given a namespace - essentially a prefix to the names in the repository. For example, my pyvenv-nwra repo could be given that prefix - and marked as such - say with pyvenv-nwra:. Then when depsolving dnf would allow dependencies in the pyvenv-nwra repo to be satisfied by packages in base repositories but not allow the reverse. Installed packages/depnames would be given the pyvenv-nwra: prefix to keep them separate from the system resources. This strikes me as a complicated technical challenge, so I really would like to hear back from the packaging ecosystem folks their thoughts about it. But I really think this could move us into the model of providing software stacks targeting different applications with different package/version requirements that build upon a stable OS core while still allowing for the tracking and deployment benefits of using rpm packages. And by having pre-populated buildroots that make any needed macro changes (say %_prefix), many packages could be built unmodified from the Fedora git repos as opposed to having to hack in the namespace prefixes into the spec files. - Orion -- Orion Poplawski Technical Manager 303-415-9701 x222 NWRA/CoRA Division FAX: 303-415-9702 3380 Mitchell Lane orion(a)cora.nwra.com Boulder, CO 80301 http://www.cora.nwra.com