Add option to `simul.py` to set size of a non-cloud cluster

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Add an option to the `OrchestratorSimulator` class in `simul.py`, that
sets the size of a non-cloud cluster.  

In more detail: add an integer argument to the class constructor;
assume it is called `cluster_size`.  Then the simulator should only
start VMs when `cluster_size` CPUs have been allocated to running
jobs.  In other words, it has `cluster_size` CPUs to manage that do
not require starting a VM.

Original issue reported on code.google.com by riccardo.murri@gmail.com on 30 Jan 2012 at 8:41

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Question:
How should this variable 'cluster_size' variate during time? 

Original comment by tyanko.a...@gmail.com on 7 Feb 2012 at 9:50

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| How should this variable 'cluster_size' variate during time?

It shouldn't.

It's meant to represent the amount of cluster hardware available, so
consider it a constant; we do not simulate the variations in the
cluster hardware over time.

Original comment by riccardo.murri@gmail.com on 7 Feb 2012 at 10:00

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I followed this logic (to be better checked):
- created the "cluster_size" variable, can be passed as option. 
- on this basis simul.py creates "cluster_size" VMs with an vm.ever_running = 
True, the otherwise: vm.ever_running = False. 
- if the VM is an ever_running "last_idle" is always 1 (if no jobs are 
running), thus jobs can start immediately. So, it si binary (Free/Occupied) 
host. 
- ever_running VMs are never considered for the calculation (+/-) of 
self._idle_vm_count.
- on stop_vm() only NOT ever_runnig VMs are considered.

Original comment by tyanko.a...@gmail.com on 7 Feb 2012 at 5:01

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Original comment by tyanko.a...@gmail.com on 7 Feb 2012 at 5:04

• Changed state: Fixed