Open Stack

Now that we have an API working group forming, I'd like to kick off some
discussion over one point I'd really like to see our APIs using (and
I'll probably drop it in to the repo once that gets fully set up): the
difference between synchronous and asynchronous operations.  Using nova
as an example—right now, if you kick off a long-running operation, such
as a server create or a reboot, you watch the resource itself to
determine the status of the operation.  What I'd like to propose is that
future APIs use a separate "operation" resource to track status
information on the particular operation.  For instance, if we were to
rebuild the nova API with this idea in mind, booting a new server would
give you a server handle and an operation handle; querying the server
resource would give you summary information about the state of the
server (running, not running) and pending operations, while querying the
operation would give you detailed information about the status of the
operation.  As another example, issuing a reboot would give you the
operation handle; you'd see the operation in a queue on the server
resource, but the actual state of the operation itself would be listed
on that operation.  As a side effect, this would allow us (not require,
though) to queue up operations on a resource, and allow us to cancel an
operation that has not yet been started.

Thoughts?
-- 
Kevin L. Mitchell <kevin.mitchell at rackspace.com>
Rackspace