[openstack-dev] [all][tc][cinder][mistral][manila] A path forward to shiny consistent service types

Ben Swartzlander ben at swartzlander.org
Mon May 1 14:44:36 UTC 2017

On 04/28/2017 06:26 PM, Monty Taylor wrote:
> Hey everybody!
> Yay! (I'm sure you're all saying this, given the topic. I'll let you
> collect yourself from your exuberant celebration)
> == Background ==
> As I'm sure you all know, we've been trying to make some hearway for a
> while on getting service-types that are registered in the keystone
> service catalog to be consistent. The reason for this is so that API
> Consumers can know how to request a service from the catalog. That might
> sound like a really easy task - but uh-hoh, you'd be so so wrong. :)
> The problem is that we have some services that went down the path of
> suggesting people register a new service in the catalog with a version
> appended. This pattern was actually started by nova for the v3 api but
> which we walked back from - with "computev3". The pattern was picked up
> by at least cinder (volumev2, volumev3) and mistral (workflowv2) that I
> am aware of. We're also suggesting in the service-types-authority that
> manila go by "shared-file-system" instead of "share".
> (Incidentally, this is related to a much larger topic of version
> discovery, which I will not bore you with in this email, but about which
> I have a giant pile of words just waiting for you in a little bit. Get
> excited about that!)
> == Proposed Solution ==
> As a follow up to the consuming version discovery spec, which you should
> absolutely run away from and never read, I wrote these:
> https://review.openstack.org/#/c/460654/ (Consuming historical aliases)
> and
> https://review.openstack.org/#/c/460539/ (Listing historical aliases)
> It's not a particularly clever proposal - but it breaks down like this:
> * Make a list of the known historical aliases we're aware of - in a
> place that isn't just in one of our python libraries (460539)
> * Write down a process for using them as part of finding a service from
> the catalog so that there is a clear method that can be implemented by
> anyone doing libraries or REST interactions. (460654)
> * Get agreement on that process as the "recommended" way to look up
> services by service-type in the catalog.
> * Implement it in the base libraries OpenStack ships.
> * Contact the authors of as many OpenStack API libraries that we can find.
> * Add tempest tests to verify the mappings in both directions.
> * Change things in devstack/deployer guides.
> The process as described is backwards compatible. That is, once
> implemented it means that a user can request "volumev2" or
> "block-storage" with version=2 - and both will return the endpoint the
> user expects. It also means that we're NOT asking existing clouds to run
> out and break their users. New cloud deployments can do the new thing -
> but the old values are handled in both directions.
> There is a hole, which is that people who are not using the base libs
> OpenStack ships may find themselves with a new cloud that has a
> different service-type in the catalog than they have used before. It's
> not idea, to be sure. BUT - hopefully active outreach to the community
> libraries coupled with documentation will keep the issues to a minimum.
> If we can agree on the matching and fallback model, I am volunteering to
> do the work to implement in every client library in which it needs to be
> implemented across OpenStack and to add the tempest tests. (it's
> actually mostly a patch to keystoneauth, so that's actually not _that_
> impressive of a volunteer) I will also reach out to as many of the
> OpenStack API client library authors as I can find, point them at the
> docs and suggest they add the support.
> Thoughts? Anyone violently opposed?

I don't have any problems with this idea. My main concern would be for 
backwards-compatibility and it sounds like that's pretty well sorted out.

I do think it's important that if we make this improvement that all the 
projects really do get it done at around the same time, because if we 
only implement it 80% of projects, it will look pretty weird.

> Thanks for reading...
> Monty
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