[one-dev] VirtualMachineManagerDriver.rb

[Ruben S. Montero]

Hi

On Sun, Aug 31, 2014 at 5:08 PM, Andrea Gardiman <andreagardiman at gmail.com>
wrote:

> Hi,
> I'm working on OpenNebula v. 4.4.1.
> I have found that the function get_first_runable in the driver
> VirtualMachineManagerDriver.rb has a limitation in the number of concurrent
> thread per node, when the action has the attribute ":host".
> In fact the function returns the index of an action only if there isn't
> another thread that is working on the same host.
> Why there is such a limitation?
>


This has been a result of a trial and error experience. In practice, some
hypervisors are very bad at performing concurrent operations, specially
libvirt/qemu. So booting several VMs at the same time (or any other
operation for the matter of fact) usually hangs some requests.

When you are interfacing the hypervisor we implemented a "host lock" to
improve the reliability. This could be relaxed in the future for KVM or now
for any hypervisor that is able to handle concurrent requests.


>
> The only wrong situation that come to my mind is when there are two
> threads that are executing actions that regard the same VM. But in that
> case should be a limitation per VM ID, not per node.
>
> Am I missing something?
>
> Thank you very much,
>  Andrea Gardiman
>
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>
>


-- 
-- 
Ruben S. Montero, PhD
Project co-Lead and Chief Architect
OpenNebula - Flexible Enterprise Cloud Made Simple
www.OpenNebula.org | rsmontero at opennebula.org | @OpenNebula
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