Hello Everyone,
In the ppb meeting last week[1] we discussed third party apis and decided that
the policy is not to include them in core. Specifically the motion that passed
is:
An OpenStack project will support an official API in it's core implementation
(the OpenStack API). other APIs will be implemented external to core. the core
project will expose stable, complete, performant interfaces so that 3rd party
APIs can be implemented in a complete and performant manner.
So now that we have settled on a long term goal for third party apis, we need
to deal with the short term. We do have a stable interface in Nova in the form
of the OpenStack API but it remains to be seen whether it is complete and
performant enough to allow other apis to be layered on top of it.
Ultimately, I would like to see a stable internal python api that the other
apis could speak through (including the OpenStack api layer), but it will
probably take a while to get there. In the short term I see three possibilities
for third party apis.
1 Proxy Layer
This is the approach being taken by AWSOME, and it is definitely the easiest to
maintain. It has some big advantages, like allowing new apis deployed in a
completely decoupled manner. The main potential drawbacks are performance and
an incomplete mapping of concepts from one api to another. This will most
likely require adding OpenStack api extensions to support some of the extra
features in other apis
2 Separate Project that talks to internal apis
It is possible to write a separate component that imports the compute.api in
nova and uses it directly. This will deal with the performance issues of the
above approach, but it runs the risk of being broken if the compute.api changes
over the course of the release. The advantage of this approach is it will drive
requirements for having a stable/versioned internal api. In this model,
automated testing would be necessary to alert any breakages.
3 Feature Branch in Core
We are doing some work to support Feature and Subsystem branches in our CI
system. 3rd party apis could live in a feature branch so that they can be
tested using our CI infrastructure. This is very similar to the above solution,
and gives us a temporary place to do development until the internal apis are
more stable. Changes to internal apis and 3rd party apis could be done
concurrently in the branch and tested. Once the branch has stabilized, the
updates could be pushed into the internal apis in nova, and the 3rd party api
could grow up into its own project like option 2
It may be that there are other options that I haven't thought of, but
regardless of the approach taken by the various 3rd party apis, I think it is
valuable for us all to work together on stabilizing the internal apis. I'd
like the ec2 api to be able to live separately as well.
Vish
[1]
http://eavesdrop.openstack.org/meetings/openstack-meeting/2012/openstack-meeting.2012-05-08-20.00.log.txt
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