What's really needed is a reserve API. It would be a big undertaking though as that concept is not in any of the network and storage plugins.
--alex > -----Original Message----- > From: David Nalley [mailto:da...@gnsa.us] > Sent: Monday, February 3, 2014 6:10 AM > To: dev@cloudstack.apache.org > Cc: Prachi Damle > Subject: Re: [PROPOSAL] Introduce API returning you an answer from > CloudStack storage/host allocators whethere there is enough resources for > vm deployment > > Hi Alena: > > I am not sure that I see a ton of value in this - and let me explain why: > > 1. This could potentially be an information disclosure issue - Could I > potentially see how much storage or other resources are available. > Does > > 2. At any scale things are going to potentially change rapidly, so a delay of > 5 > minutes may mean that the content is outdated and no longer valid. > > 3. Most importantly deploying a single machine isn't interesting, and why > would I bother checking. (And this also brings up one of the things I find > lacking in the deployVM API call.) What I'd be interested in knowing is > whether I could deploy 5, 50, or 500 machines. Perhaps adding a count > parameter to the deployVirtualMachine would help (and the corresponding > API call to check that resources are > available.) > > --David > > On Fri, Jan 31, 2014 at 7:26 PM, Alena Prokharchyk > <alena.prokharc...@citrix.com> wrote: > > Currently there is no way to know if there is enough resources for vm > deployment, before actual deployVm call is made. The sequence is the > following: > > > > 1) Deploy Vm is called > > 2) DB record is created for the Vm > > 3) Storage/Host allocators determine whethere there are enough > resources for vm to be deployed, and return deploy destination to the caller > stack. > > 4) If allocator returns valid deploy destination, VM gets actually > created/started on the backend. If allocators don't return the destination, > the DB record created on step 2) gets destroyed, and ResourceAllocation > exception is thrown back to the API caller. > > > > The API I'm going to introduce, would help you to determine whether CS > physical resources - hosts, storages - can potentially accomodate vm > deployment (considering template/service/diskOffering) at a given time, > w/o actually calling the deploy vm. Some admins might find this call useful as > they can always make this check before submitting the deployVm, so in case > it returns NO, you can fail the deployment immediately, w/o calling > deployVm. Also you can make this call to determine what is lacking for certain > vm deployment, and expand your physical resources accordingly. > > > > Please let me know if see any pitfalls in the proposal, as well if you see > > any > other use cases that can be solved using this API. > > > > Prachi, can you please point me to an existing method (or interface) > defined in Allocators code serving this purpose? > > > > Thanks, > > -Alena.
