[tahoe-dev] [tahoe-lafs] #708: graceful handling of capabilities in a format from the future that you can't understand

[tahoe-lafs]

#708: graceful handling of capabilities in a format from the future that you
can't understand
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     Reporter:  zooko          |       Owner:  warner               
         Type:  enhancement    |      Status:  closed               
     Priority:  major          |   Milestone:  1.5.0                
    Component:  code-encoding  |     Version:  1.4.1                
   Resolution:  fixed          |    Keywords:  forward-compatibility
Launchpad_bug:                 |  
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Changes (by zooko):

  * status:  new => closed
  * resolution:  => fixed


Comment:

 Over on [comment:5:ticket:683 ticket #683, comment 5], Brian wrote:

 > [3960] changes the way dirnodes are processed to tolerate unrecognized
 URIs. This should make tahoe-1.5 able to survive new formats that come
 from the future (i.e. if a 1.5 client tries to read or modify a directory
 which has new-format entries which were placed there by some 1.6-or-beyond
 version). It's at least a start.

 As I understand it, the fact that we can't add unknown caps into a
 directory means that we can't copy directories which contain caps from the
 future.  (If we do copy such a directory then the entries in it which had
 new-style caps will be omitted from the newly created copy of the
 directory).  In theory it should be possible to do that safely just by
 copying the write-cap field from the entry in the source dir into the
 write-cap field of the newly created entry in the target dir, and likewise
 copying the read-cap.

 Brian: would there be any danger in that approach?

 I don't know how important it would be for clients from the past to be
 able to copy your new-style caps.

-- 
Ticket URL: <http://allmydata.org/trac/tahoe/ticket/708#comment:6>
tahoe-lafs <http://allmydata.org>
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