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How are VM-related actions handled by Nova?

asked 2014-10-24 03:42:18 -0600

affo gravatar image

updated 2014-10-24 06:59:15 -0600

Hi everybody,
we are developing for academic interest a service for Nova which tries to achieve resource optimization.
We already saw that somebody noticed that Nova hasn't nothing which does this.

Given this, a first question: do you know if the state of the art is still unchanged? Or there is some work related which is not included in the link above?

Going further, to develop the service, we have to know how actions on VMs (such as create, delete, resize and so on) are handled by Nova.
We have already read (and understood) a lot of code from github.
For instance, we understood that (correct me if I am wrong, please):

  • the creation and the resize of a VM passes through the scheduler (only to determine the destination host)
  • the delete of a VM doesn't cause any other service to take autonomic decisions such as consolidating VMs. For instance, if host A has only one VM, some service could live migrate the instance to host B and put host A in standby to optimize resources.

The real problem is that Nova is really really big and we are scared of missing something crucial.

So, the second question is: do you know of some documentation in OpenStack which well describes this processes? Do we have to continue on this direction and continue looking at the code?

Thank you in advance

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answered 2014-10-24 04:32:59 -0600

foexle gravatar image

Hi Affo,

as far as i know thers no related features or projects plannes but to get a 100% answer you should join #openstack-nova in IRC or writing a mail to the dev mailing list. The dev mailing list is a good entry point here for your questions.

So i'm not really confirm with the code of nova but i try to get answer for your questions:

1) the creation and the resize of a VM passes through the scheduler Yes and no. The scheduler decides with filters and weighters on which compute node the new instance will spawn (create). Resize is the same way .... but the startup will be triggered by nova-compute and your hypervisor. So the scheduler don't have any todo with the real creation and startup process.

2) the delete of a VM doesn't cause any other service to take autonomic decisions This questions is unclear what do you mean ?

The best entry is the dev doc

Cheers Heiko

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Thank you very much for your answer!

I edited the post to better explain point 2

affo gravatar imageaffo ( 2014-10-24 06:59:28 -0600 )edit

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Asked: 2014-10-24 03:42:18 -0600

Seen: 150 times

Last updated: Oct 24 '14