Re: decision process to accept new libraries

On Fri, Feb 24, 2017 at 02:17:31PM +0100, Olivier Matz wrote:

On Fri, 24 Feb 2017 11:33:11 +0000, Remy Horton [off-list ref]
wrote:

quoted

On 22/02/2017 19:06, Dumitrescu, Cristian wrote:
[..]

quoted

This essentially leads to the "other" repos becoming second class
citizens that can be broken at any time without prior notice or the
right to influence the change. The amount of maintenance work
becomes very difficult to quantify (e.g. we all know what a ripple
effect a chance in the mbuf structure can cause to any  of those
"other" DPDK libraries).  

+1 - In my experience anything other than a single repository ends up
in tears sooner or later. At a previous company I worked on a project
where each "module" went into its own repo, all fourty-five of which
were strung together using Gerrit/Jenkins, the result being I spent
more time on rebases and build breakages than writing business logic.
Patchsets that cross repo boundaries are a recipe for pain, and if
DPDK goes down the same route, it will likley cripple development.

On the other hand, I think we can agree that everything that depends on
dpdk cannot be hosted in dpdk repository.

Many applications are hosted in other repositories: for instance pktgen
or vpp. A given version of these applications runs on a given version of
dpdk. It could also applies for libraries.

Having apps/libs outside the dpdk repo is more work for their
maintainers because they may need to revalidate (compilation + test) for
each dpdk version. Having them inside the dpdk repo is more work for
the maintainers of dpdk core libs, because they need to update all of
them when they do a big changes. This is sometimes not doable because
they don't have a test platform or knowledge for each pmd or lib.

Maybe not, and I wouldn't expect someone making a change to have to test
every library affected by the change. However, I would expect them to have
enough knowledge of the change being made to update the affected code in
other libraries in a semi-mechanical way, and ensure it compiles. If you
are changing a core library and are not able to change all uses of the
API yourself, then you really need to question if the change is a good
one or not, or if you are qualified to make a change if you don't
understand how the old code was being used.

I also think it's likely that many users of DPDK code will have legacy
code using DPDK, for which the original programmer may be the one making
any updates. If, again, the change is such that it can't be done in a
relatively mechanical way, that is going to be a problem for all those
users.

As for review and testing, that is the responsibility of the maintainers
and validators responsible for the individual library being updated.

/Bruce