[one-users] Scheduler approach on impossible results

Tino Vazquez tinova79 at gmail.com
Thu Sep 29 08:33:19 PDT 2011

Dear Vinicius,

This is an interesting issue indeed. I've opened a ticket to keep track of it:




Constantino Vázquez Blanco | dsa-research.org/tinova
Virtualization Technology Engineer / Researcher
OpenNebula Toolkit | opennebula.org

2011/9/14 Vinícius Vielmo Cogo <vielmo at inf.ufsm.br>:
> Hello,
> We have one question/suggestion regarding the approach of the scheduler face
> to an result of impossibility on resource allocation process.
> As the OpenNebula default matchmaking scheduler is an immediate lease
> scheduler, it should always return the allocated resources or an error due
> to it's impossibility. But, when the scheduler receives an expression which
> turns to an impossible result, the VM remains in pending state indefinitely,
> which is an approach related with best-effort schedulers.
> Specifically in our case, we want to deploy one Virtual Machine on each host
> of our cloud (for security reasons) and we don't want to obtain all
> information about the entire HostPool in each VM creation (scalability
> reasons).
> The problem arises when we achieve the entire set of hosts inside of our
> requirements (e.g using "HOSTNAME != \"some-host\"" & "HOSTNAME !=
> \"another-host\"", etc), which means that don't exist other host to allocate
> the Virtual Machine.
> This approach also can be considered one of the reasons that contributed for
> other similar issues pointed on mailing list, as for example, on [one-users]
> VM creation stuck in "pending" state thread, where the same problems could
> be solved if the OpenNebula would changed the VM state to fail and logged
> the appropriate output.
> We believe that there are at least two main possibilities to circumvent this
> problem:
> 1) Change the VM state to "fail" when an impossible result is achieved.
> 2) Add a new state for the virtual machine to indicate when it achieve an
> impossible result (for example, an impossible state).
> We would like to know your opinion about this approach, if it's possible to
> modify the OpenNebula scheduler in those terms and/or if you could indicate
> other ways to avoid this pending issue.
> Thank you in advance.
> Vinicius Vielmo Cogo
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