As I understand this is a best-effort approach. Even if the proposed API 
returns YES, deployment may still fail. I personally feel that it is better to 
improve the deployVM API itself to return accurate error message rather than 
having multiple API calls. If the deployvm call call fails, it will clearly 
indicate reason for failure so appropriate action can be taken.

-Koushik

On 03-Feb-2014, at 12:35 PM, Rajani Karuturi <rajani.karut...@citrix.com> wrote:

> I agree with Santhosh. Returning appropriate error codes might be enough. 
> 
> Thanks,
> ~Rajani
> 
> 
> 
> On 02-Feb-2014, at 11:17 pm, Santhosh Edukulla <santhosh.eduku...@citrix.com> 
> wrote:
> 
>> Just a note:
>> 
>> Instead of making two separate api calls one to check and then for deploy, 
>> may be it can be part of deploy only and check these conditions for 
>> resources\any other information and return appropriate codes? This check can 
>> be called firsthand as part of deploy\other commands applicable and return 
>> with codes before proceeding further with steps of deploy mentioned.
>> 
>> Thanks!
>> Santhosh
>> ________________________________________
>> From: Daan Hoogland [daan.hoogl...@gmail.com]
>> Sent: Saturday, February 01, 2014 11:24 AM
>> To: dev
>> Subject: Re: [PROPOSAL] Introduce API returning you an answer from 
>> CloudStack storage/host allocators whethere there is enough resources for vm 
>> deployment
>> 
>> I like the idea.  Would the api query the db or the bakends (i.e. hosts,
>> storage,  etc)?
>> 
>> mobile bilingual spell checker used
>> Op 1 feb. 2014 17:13 schreef "abhisek basu" <abhisekb...@msn.com>:
>> 
>>> Great idea, this would certainly reduce vm deployment failures.
>>> 
>>> VR including RVR if needs to be created, should get included in this check.
>>> 
>>> Also, can we include ways to check if a VM can be launched in a certain
>>> cluster? The idea is to allow users / admins to  be able to launch vm in a
>>> certain cluster, but that might be the next functionality.
>>> 
>>> Sent from my iPhone
>>> 
>>>> On 1 Feb 2014, at 8:50 pm, "Ryan Lei" <ryan...@cht.com.tw> wrote:
>>>> 
>>>> I believe it's a nice idea. A lot of us have experienced the
>>>> annoying InsufficientCapacityException in Deploying Virtual Machines, but
>>>> we can't tell exactly why just by reading the logs.
>>>> 
>>>> If this new API could help us debug this VM deployment process to
>>> determine
>>>> exactly which resource is lacking, or probably other internal reasons
>>> that
>>>> cause this InsufficientCapacityException, it would be very helpful!
>>>> 
>>>> 
>>> -------------------------------------------------------------------------------------------
>>>> Yu-Heng (Ryan) Lei, Associate Researcher
>>>> Cloud Computing Dept, Chunghwa Telecom Labs
>>>> ryan...@cht.com.tw or ryanlei750...@gmail.com
>>>> 
>>>> 
>>>> 
>>>> On Sat, Feb 1, 2014 at 8:26 AM, 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.
>>>>> 
>>> 
> 

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