Open Stack

 I was wondering if anyone has an idea of how queuing can be achieved in 
 Openstack.
 Is everybody using there own custom made way or is there something more 
 universal?

 If for example I want to spawn a new VM but there are aren't available 
 resources
 then the spawn will fail with the "no available resources" error. So, 
 is there a way
 to keep that in a queue until resources are available and spawn 
 automatically only then?

 Regards,

 George