On 13 May 2009, at 15:50, Chris Webb wrote:
Sam Johnston <samj@samj.net> writes:
So the question is do you ask a "RUNNING" resource to "STOP" by pressing a button in order to get it to the "STOPPED" state or do you update its status from "RUNNING" to "STOPPED". To me the latter is unclean because who are you to say you're going to get to that state immediately, or indeed that you'll even get there at all
Indeed. We have a classic example of this in our own public cloud. For us, guests can go away by being 'destroyed' (hard kill) or because the operating system inside has executed an ACPI power-down, essentially asking to be destroyed.
We have an action 'shutdown' which sends an ACPI power-button event to the guest OS. This may result in a successful shutdown (leading to an ACPI power-down and guest destruction), it may be ignored, or it may trigger something completely different. (I've used it for server-wide SIGHUP- type behaviour before.)
Hi Chris, Maybe I miss something, but, given the above, and supposing it does go wrong (doesn't end up where you expected), how do you discover, a while later, why that it so ? Roger
Because of this, even ignoring the delay in state change, it's not clear that our 'shutdown' event meaningfully maps to any particular state change because from outside the vm abstraction: we don't know what effect on state the power-button event will actually have!
Cheers,
Chris.
Roger Menday (PhD) <roger.menday@uk.fujitsu.com> Senior Researcher, Fujitsu Laboratories of Europe Limited Hayes Park Central, Hayes End Road, Hayes, Middlesex, UB4 8FE, U.K. Tel: +44 (0) 208 606 4534 ______________________________________________________________________ Fujitsu Laboratories of Europe Limited Hayes Park Central, Hayes End Road, Hayes, Middlesex, UB4 8FE Registered No. 4153469 This e-mail and any attachments are for the sole use of addressee(s) and may contain information which is privileged and confidential. Unauthorised use or copying for disclosure is strictly prohibited. The fact that this e-mail has been scanned by Trendmicro Interscan and McAfee Groupshield does not guarantee that it has not been intercepted or amended nor that it is virus-free.