Re: [Xen-devel] Many same managed domain

[Masaki Kanno <kanno.masaki@xxxxxxxxxxxxxx>]

>On Sun, Jul 22, 2007 at 02:09:01PM +0900, Masaki Kanno wrote:
>> Hi,
>> 
>> When I tested xm new command without uuid parameter repeatedly, 
>> I saw many same managed domain as follows. 
>> 
>> # xm list
>> Name                                        ID   Mem VCPUs      State   
>> Time(s)
>> Domain-0                                     0   941     2     r-----    
>>  51.9
>> # xm new /xen/vm1.conf 
>> Using config file "/xen/vm1.conf".
>> # xm new /xen/vm1.conf 
>> Using config file "/xen/vm1.conf".
>> # xm new /xen/vm1.conf 
>> Using config file "/xen/vm1.conf".
>> # xm list
>> Name                                        ID   Mem VCPUs      State   
>> Time(s)
>> Domain-0                                     0   941     2     r-----    
>>  56.3
>> vm1                                              256     1               
>>   0.0
>> vm1                                              256     1               
>>   0.0
>> vm1                                              256     1               
>>   0.0
>> 
>> 
>> But, when I tested xm new command with uuid parameter repeatedly, 
>> I did not see same managed domain as follows. 
>> 
>> # xm list
>> Name                                        ID   Mem VCPUs      State   
>> Time(s)
>> Domain-0                                     0   941     2     r-----    
>>  69.9
>> # xm new /xen/vm1.conf uuid="aaaaaaaa-bbbb-cccc-dddd-eeeeeeeeeeee"
>> Using config file "/xen/vm1.conf".
>> # xm new /xen/vm1.conf uuid="aaaaaaaa-bbbb-cccc-dddd-eeeeeeeeeeee"
>> Using config file "/xen/vm1.conf".
>> # xm new /xen/vm1.conf uuid="aaaaaaaa-bbbb-cccc-dddd-eeeeeeeeeeee"
>> Using config file "/xen/vm1.conf".
>> # xm list
>> Name                                        ID   Mem VCPUs      State   
>> Time(s)
>> Domain-0                                     0   941     2     r-----    
>>  74.4
>> vm1                                              256     1               
>>   0.0
>> 
>> 
>> I think that xm new command should cause a command error if without 
>> uuid parameter.  What do you think?
>
>No that would break backwards compatability for user who rely on Xen 
>autogenerating the UUID. 
>
>In order to maintain back-compatability with existing use cases, the user
>needs to be able to update the existing VM config with 'xm new' if the name
>or UUID match, while preventing multiple VMs with same name. So the the 
>rules 
>when defining a new VM need to follow this logic
>
>  - If the UUID is not specified
>        - If a VM with same name exists
>            => Update the config for that existing VM
>        - Else no vm with same name exists
>            => Define a brand new VM with auto-generated UUID
>  - Else UUID is specified
>        - If a VM with same UUID exists
>              - If name is different
>                    => Error
>              - Else if name is same
>                    => Update the config for that existing VM
>       - Else no VM with same UUID exists
>            => Define a branch new VM with that name

Thanks for your explanation. 
I have a question to your logic.  I think that the logic need a VM 
name check when no VM with same UUID exists.  Am I right?

  - If the UUID is not specified
        - If a VM with same name exists
            => Update the config for that existing VM
        - Else no vm with same name exists
            => Define a brand new VM with auto-generated UUID
  - Else UUID is specified
        - If a VM with same UUID exists
              - If name is different
                    => Error
              - Else if name is same
                    => Update the config for that existing VM
        - Else no VM with same UUID exists
-           => Define a branch new VM with that name
+             - If name is different
+                   => Define a branch new VM with that name
+             - Else if name is same
+                   => Error

Best regards,
 Kan



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