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Re: [Xen-API] Xen Management API draft
I also reviewed the API document this afternoon. I'll say that I'm a
bit less emphatic about this one (although I still appreciate the effort).
My basic problem is that this API is huge. I understand why most of
this stuff is included but at the same time, it greatly conflicts with
existing systems that already do this (for instance, IBM Director's CIM
What I'd like to see is a minimalistic API that only dealt with Xen
specific stuff. If you wished to have an accompanying API that also
provided other system info (via the same model) that would seem like a
rather good compromise.
We're interested in a minimalistic Xen stack. So being able to omit the
portions of this API that we don't need would be very useful.
Ewan Mellor wrote:
Attached is a draft Xen Management API. This document presents our ideas in
terms of a data model, with an implied binding to XML-RPC calls. There are a
few examples in there too -- hopefully it's clear how the mapping between the
document and the wire protocol.
Hopefully, we can standardise the data model and wire protocol (one implying
the other) and then the Xen project would guarantee that that wire protocol
would be supported for the long term. Behind that interface, we would then be
free to improve Xend, and giving a solid foundation for Xen-CIM, and third
party GUIs and tools and so on. The API becomes effectively part of the
"guarantees" for Xen.
I expect that we will be asked for client-side bindings for a number of
languages. It is my intention that a binding to any particular language would
be a very thin translation from the host language's values and types onto the
fixed XML-RPC, and then we shouldn't have too much trouble maintaining
bindings in Python or Perl or C++ or whatever people want.
This document is totally open to discussion and modification, so please, let's
In particular, we need to get this API into a state so that it is the right
API for Xen-CIM. We need to think whether libvirt is ready to rely upon this
API too. That would mean moving the hypercalls and Xenstore reads and writes
out of libvirt, and pushing it up the stack alongside the other client-side
Like the OVA spec, this document is for narrow circulation, and once we are
getting happy with it, we'll circulate it more widely. I'd like to be able to
circulate this before OLS, as that will be a good chance to discuss it with
people face-to-face once they've had a chance to read it.
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