[cap-talk] Session failures

[Jed Donnelley]

On 3/14/2008 12:16 PM, David-Sarah Hopwood wrote:
> Jed Donnelley wrote:
>> On 3/14/2008 9:28 AM, Jonathan S. Shapiro wrote:
>>> On Fri, 2008-03-14 at 09:14 -0700, Jed Donnelley wrote:
>>>> <right here lies the Two Generals problem:
>>>> http://en.wikipedia.org/wiki/Two_Generals'_Problem
>>>>
>>>> which I think helps to clarify the difficulty, indeed
>>>> the General insolubility.>
>>> Recovering consistency from independently taken snapshots turns out to
>>> be solvable. [...]
>> For my curiosity, how is it that despite the above sorts
>> of checkpoint/recovery mechanisms our two Generals still
>> can't agree whether or not to attack?
> 
> Because attacking is a non-undoable effect.
> 
> If it it were possible to roll back the effects of an attack, then there
> would be no problem: each general speculatively attacks, and then if only 
> one attack occurs, it is rolled back.

That's helpful.  Thanks David!

--Jed  http://www.webstart.com/jed/