[tahoe-dev] [tahoe-lafs] #393: mutable: implement MDMF

[tahoe-lafs]

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

 attachment:393status29.dpatch fixes all of the failing tests, so all unit
 tests should pass now. It syncs up my changes with trunk. It also
 represents a fairly substantial reorganization of the patch set, which
 will (hopefully!) make it a lot easier to review. I'm going to be
 reviewing it myself and fixing a few rough edges this week, but I'm going
 to set the review-needed keyword so that others can start reviewing it
 too.

 Rough areas that I know about:

   - {{{_loop}}} in the mutable file downloader isn't hooked up to
 anything. I took it out of the path of execution when we were still doing
 multiple-write uploads, but it makes sense to use it again now that we're
 back to single-write uploads, as in SDMF, since it will allow us to place
 more shares than we would otherwise in certain circumstances. I'm going to
 hook it back up tomorrow.
   - Neither the uploader nor the downloader are very good about keeping
 their status objects updated. I'm going to try to address this tomorrow.
   - The way that you tell a mutable file whether it is SDMF or MDMF is
 poorly specified and kind of a kludge that I made a while ago to help me
 test things. It probably needs to be at least looked at, specified more
 precisely, and maybe changed. Right now, if you upload a mutable file that
 is larger than 128KiB, it is automatically made to be MDMF; otherwise, it
 is SDMF. These semantics are probably not what we want for backward
 compatibility/interoperating with older clients.
   - I need to look at the deferred chains in the publisher and downloader
 to make sure that I'm not going to be causing ballooning memory usage due
 to tail recursion.

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Ticket URL: <http://tahoe-lafs.org/trac/tahoe-lafs/ticket/393#comment:56>
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