[tahoe-lafs-trac-stream] [tahoe-lafs] #393: mutable: implement MDMF

[tahoe-lafs]

#393: mutable: implement MDMF
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     Reporter:  warner   |      Owner:  zooko
         Type:           |     Status:  new
  enhancement            |  Milestone:  1.9.0
     Priority:  major    |    Version:  1.0.0
    Component:  code-    |   Keywords:  newcaps performance random-access
  mutable                |  privacy gsoc mdmf mutable backward-
   Resolution:           |  compatibility forward-compatibility review-
Launchpad Bug:           |  needed
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Comment (by kevan):

 I think I agree with comment:128, comment:129, comment:130 and
 comment:136; I've made those fixes in my tree.

 That comment on {{{_upload}}} is a bit confusing. You're correct that
 there's no restriction (either in the code or in the semantics prescribed
 by IMutableFileNode) that upload be used only for new mutable files. I'll
 remove that. I probably put it there because the only internal caller of
 {{{_upload}}} is associated with mutable file creation.

 I'll attach a patch with those fixes and a few others (removing some TODOs
 in the mutable filenode code that no longer apply, removing SDMF-specific
 comments from interfaces.py, and removing a commented-out method from the
 mutable filenode code).

 On the call yesterday, we had some concerns about fencepost errors in
 segment boundary calculations, and in particular their potential impact on
 SDMF mutable files. In the case of SDMF files, most of these calculations
 are easy: there's only one segment, and we always want to fetch or upload
 it. It would be fairly easy to use that knowledge to short-circuit the
 possibly wrong segment calculations so that they're only used for MDMF
 mutable files, which would reduce the potential for regression if they are
 in fact wrong. Does that seem like a good idea? I can prepare a patch with
 those changes if so.

-- 
Ticket URL: <http://tahoe-lafs.org/trac/tahoe-lafs/ticket/393#comment:139>
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