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Re: [Openstack] Thoughts on client library releasing


On 06/18/2012 02:25 PM, Doug Hellmann wrote:
> How do these plans fit with the idea of creating a unified client
> library (either as one package or several, based on a common core)?

They are kind of orthogonal. At the point where python-openstackclient
is ready for release, we'd likely want to manage it the same way.

> On Mon, Jun 18, 2012 at 5:11 PM, Monty Taylor <mordred@xxxxxxxxxxxx
> <mailto:mordred@xxxxxxxxxxxx>> wrote:
>     We're trying to figure out how we release client libraries. We're really
>     close - but there are some sticking points.
>     First of all, things that don't really have dissent (with reasoning)
>     - We should release client libs to PyPI
>     Client libs are for use in other python things, so they should be able
>     to be listed as dependencies. Additionally, proper releases to PyPI will
>     make our cross project depends work more sensibly
>     - They should not necessarily be tied to server releases
>     There could be a whole version of the server which sees no needed
>     changes in the client. Alternately, there could be new upcoming server
>     features which need to go into a released version of the library even
>     before the server is released.
>     - They should not be versioned with the server
>     See above.
>     - Releases of client libs should support all published versions of
>     server APIs
>     An end user wants to talk to his openstack cloud - not necessarily to
>     his Essex cloud or his Folsom cloud. That user may also have accounts on
>     multiple providers, and would like to be able to write one program to
>     interact with all of them - if the user needed the folsom version of the
>     client lib to talk to the folsom cloud and the essex version to talk to
>     the essex cloud, his life is very hard. However, if he can grab the
>     latest client lib and it will talk to both folsom and essex, then he
>     will be happy.
>     There are three major points where there is a lack of clear agreement.
>     Here they are, along with suggestions for what we do about them.
>     - need for "official" stable branches
>     I would like to defer on this until such a time as we actually need it,
>     rather than doing the engineering for in case we need it. But first, I'd
>     like to define we, and that is that "we" are OpenStack as an upstream.
>     As a project, we are at the moment probably the single friendliest
>     project for the distros in the history of software. But that's not
>     really our job. Most people out there writing libraries do not have
>     multiple parallel releases of those libraries - they have the stable
>     library, and then they release a new one, and people either upgrade
>     their apps to use the new lib or they don't.
>     One of the reasons this has been brought up as a need is to allow for
>     drastic re-writes of a library. I'll talk about that in a second, but I
>     think that is a thing that needs to have allowances for happening.
>     So the model that keystone-lite used - create an experimental branch for
>     the new work, eventually propose that it becomes the new master - seems
>     like a better fit for the "drastic rewrite" scenario than copying the
>     stable/* model from the server projects, because I think the most common
>     thing will be that library changes are evolutionary, and having two
>     mildly different branches that both represent something that's actually
>     pretty much stable will just be more confusing than helpful.
>     That being said - at such a time that there is actually a pain-point or
>     a specific need for a stable branch, creating branches is fairly easy
>     ... but I think once we have an actual burning need for such a thing, it
>     will make it easier for us to look at models of how we'll use it.
>      - API or major-rewrite-driven versioning scheme
>     I was wondering why bcwaldon and I were missing each other so strongly
>     in the channel the other day when we were discussing this, and then I
>     realized that it's because we have one word "API" that's getting
>     overloaded for a couple of different meanings - and also that I was
>     being vague in my usage of the word. So to clarify, a client library
>     has:
>      * programming level code APIs
>      * supported server REST APIs
>     So I back off everything I said about tying client libs version to
>     server REST API support. Brian was right, I was wrong. The thing that's
>     more important here is that the version should indicate programmer
>     contract, and if it that is changed in a breaking manner, the major
>     number should bump.
>     If we combine that with the point from above that our libraries should
>     always support the existing server REST APIs, then I think we can just
>     purely have statements like "support for compute v3 can be found in
>     2.7.8 and later" and people will likely be fine, because it will map
>     easily to the idea "just grab the latest lib and you should be able to
>     talk to the latest server" Yea?
>     So in that case, the client libs versions are purely whatever they are
>     right now, and we'll increase them moving forward using normal library
>     version thoughts.
>      - room for deprecating old APIs
>     The above then leads us to wanting to know what we do about supported
>     server REST APIs over time, especially since I keep making sweeping
>     statements about "should support all available server versions" .... How
>     about this as a straw man: Since we're planning on beginning to run
>     tests of the client libs against previous versions (so we'll test trunk
>     novaclient against essex nova in addition to trunk nova) ... we need
>     support for past versions of servers as long as our automation can
>     sensibly spin up a past version. (Since the support for that API version
>     shouldn't need huge amounts of work moving forward) But there will reach
>     a point where old server versions require stuff that's older than we
>     feel like supporting, and at that point we drop it. (or, more to the
>     point, that we reserve the right in the future to declare that we're
>     going to drop old server API versions - but the general policy is that
>     we'll keep old support until it becomes a pain in the ass)
>     Does that all sit well with folks?
>     Monty
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