Re: [Xen-API] the xapi storage interface

[Anil Madhavapeddy <anil@xxxxxxxxxx>]

On 18 Jun 2012, at 11:25, Dave Scott wrote:
> Anil wrote:
>> This is an odd one to have in the storage-specific API.  Is it
>> exactly the same Task API as the rest of the XenAPI, and 
>> duplicated because of the rpc-light interface?
>> 
>> From a client perspective, it would be good to use exactly the
>> same task/event/wakeup API for all operations, not just storage.
> 
> Yup, it's basically the same interface. I agree it would be better to share 
> it somehow -- I'll see if I can keep it separate and stop storage-specific 
> types from accreting into it. At the moment it's a bit polluted with "SR" and 
> "VDI" types but I could make it more dynamic and then wrap a type-safe layer 
> onto it for the storage implementation in particular.

Splitting up XAPI will probably have the biggest affect on the Task
API, since it is shifting from a central database to a distributed set
of processes (some of which run in dom0, and others in separate domains).
It's going to be increasingly hard to maintain a fully consistent
view of all the tasks on the system, so now may be a good opportunity to
pull together a more asynchronous, unreliable Task API that can handle
other endpoints disappearing.

This is very similar to the Erlang process tree (including having other
processes watching and restarting portions of the process namespace to
ensure availability as a top priority).

A good direction for Xenstore to move towards perhaps, given that it was
originally intended to be distributed across clusters all the way back in
2003!

-anil
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