On 04/09/2013 01:45 AM, David Lutterkort wrote:
On Mon, 2013-04-08 at 14:44 +0200, Jan Provaznik wrote:
There are some other downsides to using DC in process (as a library): it
also significantly changes where DC can go architecturally. So far, the
classic DC API has worked very hard to be stateless - CIMI isn't, and it
wouldn't be unreasonable to introduce state into the classic DC API.
That would be much more awkward if DC becomes a library.
I'm not familiar with DC plans (which sound really interesting) but even
with stateful DC the lib could make sense:
1) the DC lib - can be used by anyone who doesn't need any stateful feature
2) DC/CIMI stateful service - built *on top* of the lib, wraps the lib
with REST API, adds stateful features
I think this is the right way to slice things up: make the DC service(s)
wrappers around the DC library. The library essentially deals with
adapting the internal driver API to something stable, and probably will
make the API look a little more Rubyish. For example, right now code to
start and stop an instance would look something like
dc = Deltacloud::new(some_backend, some_provider, credentials)
inst = dc.create_instance(...)
unless starts_automatically(dc) # needs to look at
instance_states
wait_for_state(dc, inst, "STOPPED")
dc.start_instance(credentials, inst.id)
end
wait_for_state(dc, inst, "STARTED")
.. do stuff with your running instance ..
dc.stop_instance(dc, inst)
As you can see, the above isn't very Rubyish; it would be nicer to write
dc = Deltacloud::new(some_backend, some_provider, credentials)
inst = dc.create_instance(...)
if inst.initial_state == 'STOPPED'
inst.poll_for { |inst| inst.stopped? }
inst.start
end
inst.poll_for { |inst| inst.started? }
.. do stuff with your running instance ..
inst.stop
What I am mostly after is a feel for who's going to do the following
around a DC library:
* Come up with a library API that is safe to use - that includes
keeping the API stable and making sure we only expose reasonable
parts of the driver API. We don't want an automatic "It's in the
drivers, therefore it's part of the API"
* Write enough tests to convince us that the library API still
works
* Document that API
Ok .. who's raising their hand ? ;)
I'd like to participate too.
David
Jan
