7:22 p.m.
On 2012-6-20 5:32, Saggi Mizrahi wrote:
There is an important discussion starting about the future of the
VDSM API on
vdsm-devel. If you want to be involved in the future of the VDSM API don't miss
out and join vdsm-devel. To sign up go to
https://fedorahosted.org/mailman/listinfo/vdsm-devel
There growing need for a way to more easily reuse of the functionality of VDSM
in order to service projects other than Ovirt-Engine.
Originally VDSM was created as a proprietary agent for the sole purpose of
serving the then proprietary version of what is known as ovirt-engine. Red Hat,
after acquiring the technology, pressed on with it's commitment to open source
ideals and released the code. But just releasing code into the wild doesn't
build a community or makes a project successful. Further more when building
open source software you should aspire to build reusable components instead of
monolithic stacks.
We would like to expose a stable, documented, well supported API. This gives
us a chance to rethink the VDSM API from the ground up. There is already work
in progress of making the internal logic of VDSM separate enough from the API
layer so we could continue feature development and bug fixing while designing
the API of the future.
In order to achieve this though we need to do several things:
1. Declare API supportability guidelines
2. Decide on an API transport (e.g. REST, ZMQ, AMQP)
3. Make the API easily consumable (e.g. proper docs, example code, extending
the API, etc)
4. Implement the API itself
Now, VDSM version was highly bound with oVirt
Engine version. In order
to make oVirt to work, both VDSM and ovirt engine should be synced with
the latest binary, no back compatibility yet. If we want to break this
binding out, we should classify the level of the VDSM APIs like these:
1) public stable
2) public evolving
3) undocumented volatile
And the we should make sure public stable interfaces to be supported in
a very long time as possible as we can. public evolving interfaces
should keep the compatibility in the same major release(ie, 4.x.x).
undocumented volatile is not recommended to the application and it is
the responsibility of the application to take the risk.
All of these are dependent on one another and the permutations are endless.
This is why I think we should try and work on each one separately. All
discussions will be done openly on the mailing list and until the final version
comes out nothing is set in stone.
If you think you have anything to contribute to this process, please do so
either by commenting on the discussions or by sending code/docs/whatever
patches. Once the API solidifies it will be quite difficult to change
fundamental things, so speak now or forever hold your peace. Note that this is
just an introductory email. There will be a quick follow up email to kick start
the discussions. Don't forget to sign up to the vdsm-devel mailing list.
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--
Shu Ming <shuming(a)linux.vnet.ibm.com>
IBM China Systems and Technology Laboratory