[evla-sw-discuss] An "In Use" flag for the MIB interface

[Hichem Ben Frej]

We did consider the idea. The draw back is that the command syntax has 
to change. It has to include a password to be sent with every “set” 
command when the MIB is locked.

Thanks,

Hichem

Kevin Ryan wrote:
> Okay, I understand; since the servlet is running on a 'proxy server'  
> to the MIB, the MIB will always see the same IP address (the proxy's)  
> in the UDP packet.  I forgot that it was getting the 'lock/key' from  
> the packet-header.
>
> I guess then the question becomes - should we think about how this  
> will scale for the overall system?  Would it be better to supply the  
> lock at a higher level than the packet header (i.e. as an explicit  
> message-content parameter) so that the ultimate end user is  
> identified?  Just a thought.
>
> Kevin
>
>
> On Aug 15, 2006, at 2:55 PM, Hichem Ben Frej wrote:
>
>   
>> Kevin,
>>
>> Thanks for you input.
>>
>> As proposed, 2 or more processes running on the same host will have
>> equal access rights. Any MIB locked by one process is accessible  
>> for all
>> the other processes since, as you mentioned, the share the same IP  
>> address.
>>
>> We referred to the case of servlet because the "real user" in this  
>> case
>> is not the servlet but the user that is connected to the servlet.
>> Lets say that a servlet is running on a server S. User A connects to S
>> through the browser. A sends a lock command, if available. The IP
>> address used for the lock is the IP address of the machine S on which
>> the servlet is running. Let say user B connects to the same servlet
>> running on S.  User B has unlimited access to the MIB locked by user A
>> since all the commands sent, through server S, have the right password
>> ie. the same IP address. It is similar to the case mentioned above.
>>
>> Thanks,
>>
>> Hichem
>>
>> Kevin Ryan wrote:
>>     
>>> Hichem,
>>>
>>> I think this is an excellent implementation of the lock - it is nice
>>> and simple.
>>>
>>> Are there situations where two different processes on the same client
>>> would conflict (they would have the same IP address)?
>>>
>>> 'Left on locks' should simply be handled like they are in the real
>>> world; by policy -- "Anyone neglecting to remove his lock shall be
>>> punished by not more than 6 months of attending code-walkthroughs"
>>> It would be complicated to implement software that could prevent  
>>> left-
>>> on-locks.
>>>
>>> Also, I don't think I understand what you mean by the servlet/applet
>>> thing not working.  Servlets, at least, should work because they have
>>> knowledge of the remote client's IP address.  And I would think
>>> Applets could send the client's IP back to the remote server (the  
>>> MIB).
>>>
>>> Or am I misunderstanding something?
>>>
>>> Kevin
>>>
>>>
>>> On Aug 15, 2006, at 12:04 PM, Bill Sahr wrote:
>>>
>>>
>>>       
>>>> Any application that locks through a servlet or applet is not
>>>> guaranteed
>>>> to have exclusive use of a lock because all other applications going
>>>> through the same servlet or application will be seen as having  
>>>> set the
>>>> lock, i.e., will have the same originator IP address (the password).
>>>>
>>>>         
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>>>
>>>       
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