Sorry if I'm oversimplicating this, as I'm no core dev, so please ignore or correct me where I'm wrong: Can't you simply define a versioned interface between vdsm and engine ? this interface can be split up in different sections: section a) must be reported : since 3.5 item 1 : all versions item 2 : since 3.4 item 3 : since 3.5 section b) can be reported if data is available : since 3.5 item 1 item 2 section c) ??? as you can see, you can even version the sections with all data prior to the integration of this interface falling into section a) or a special section for backwards compatibility. If such a thing doesn't exist yet it's maybe hard to introduce, but worth it. HTH Am 09.04.2014 16:25, schrieb Dan Kenigsberg:
But Vdsm cannot make this decision. Soon, Vdsm is to report the host's boot time. Now assume that Vdsm fails to do so. Is the stats "partial"? It's partial for engine-3.5, but it's complete for engine-3.4.
Vdsm should tell as much of the truth that it knows.
We could extend the "alerts" mechanism to report non-lethal errors in getVmStats (we currently have it only in for storage domain status), where Engine is told what's missing and why. I'm not sure if this is really needed, though.
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