Sam/Chris,

                Good work. Couple of points.

a) The diagram needs a entry and exit point circles (actually concentric circles)

b) The Stopping and Starting states are important. For example if the state is Starting, clients could retry; schedulers could add the VM in their pool et al. Stopping state will mean that the system is not accepting service requests anymore. It might have to stay in this state until all pending requests are completed.

c) There is another state Aborting – don’t know if we want to add this.

d) The stopped state, while not important during run time, will be useful for account keeping, auditing et al. For example a log entry with Stopped state with a timestamp

e) Remember, monitoring and billing is an important plane for Clouds and so we should also have states that are relevant from that perspective …

Cheers

<k/>

From: occi-wg-bounces@ogf.org [mailto:occi-wg-bounces@ogf.org] On Behalf Of Sam Johnston
Sent: Saturday, April 18, 2009 6:14 AM
To: Chris Webb
Cc: occi-wg@ogf.org
Subject: Re: [occi-wg] OCCI MC - State Machine Diagram

On Sat, Apr 18, 2009 at 1:43 PM, Chris Webb <chris.webb@elastichosts.com> wrote:

Sam Johnston <samj@samj.net> writes:

> I have created a diagram (attached) of what I think the absolute minimum
> core states need to be... essentially boiling them down to "STOPPED" and
> "ACTIVE" with "START" and "STOP" being the only requisite actuators.
> Transitional "STOPPING" and "STARTING" states are optional.

+1

I strongly agree with simplifying things in this way. Good stuff!

I subsequently realised that in fact infrastructure like Amazon, Mosso and ElasticHosts don't actually have a "stopped" state - "stop" for these guys is more like "destroy".

It then occurred to me that there was no point making "stopped" optional as if you don't need to start/stop/restart machines then you just don't implement the machine control extension. It's far easier to create (HTTP PUT) and then destroy (HTTP DELETE) a server than what it is to parse the response to fire an actuator.

So basically the machine control extension becomes optional (but possibly still interesting to indicate transitional states like "starting" and "stopping" as Chris pointed out privately).

Sam