[tahoe-dev] several newbie questions

[Kevin Reid]

On Apr 21, 2011, at 8:58, Miles Fidelman wrote:

> There are several questions - answers to which elude me in perusing  
> the various publications, presentations, and documentation on  
> Tahoe.  I wonder if anybody can comment:
>
> 1. Tahoe seems to support multi-writer mutable files - but I can't  
> seem to find any discussion of consistency management and conflict  
> resolution mechanisms.  Are there any, and if so, can someone point  
> me at some documentation?

<http://tahoe-lafs.org/trac/tahoe-lafs/browser/trunk/docs/specifications/mutable.rst#the-prime-coordination-directive-don-t-do-that 
 >

“The current rule for applications which run on top of Tahoe is "do  
not perform simultaneous uncoordinated writes". That means you need  
non-tahoe means to make sure that two parties are not trying to modify  
the same mutable slot at the same time.”

“If you do not follow this rule, Bad Things will happen. The worst- 
case Bad Thing is that the entire file will be lost. A less-bad Bad  
Thing is that one or more of the simultaneous writers will lose their  
changes. An observer of the file may not see monotonically-increasing  
changes to the file, i.e. they may see version 1, then version 2, then  
3, then 2 again.”

> 2. Looking at the capability mechanisms, it's not clear to what  
> extent capabilities are bound to individuals.  The standard problem  
> with key-based capabilities mechanisms is that they can be copied.

That's a feature, not a bug.

-- 
Kevin Reid                                  <http://switchb.org/kpreid/>