[tahoe-dev] [tahoe-lafs] #287: download: tolerate lost or missing servers

tahoe-lafs trac at allmydata.org
Mon Feb 1 01:31:49 UTC 2010


#287: download: tolerate lost or missing servers
---------------------------------------------------------+------------------
 Reporter:  warner                                       |           Owner:            
     Type:  defect                                       |          Status:  new       
 Priority:  major                                        |       Milestone:  eventually
Component:  code-encoding                                |         Version:  0.7.0     
 Keywords:  download availability performance test hang  |   Launchpad_bug:            
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Comment(by zooko):

 I think that the original post was slightly imprecise. I think that
 download ''would'' correctly fail-over if a server disconnected during
 download (or if the server returned an error or if it dropped the TCP
 connection), but it would hang if the server stayed connected but didn't
 answer the requests at all. In fact, until the fix for #928 was committed,
 downloads would hang if there was such a stuck server on the grid at all,
 even if that server had been in its stuck state since before the download
 began and even if that server didn't have any of the shares that the
 download needed!

 Okay, so the fix for #928 has been committed to trunk, which means that
 downloads now proceed even if there is a stuck server on the grid ''but''
 with the current version ([4207]) it means that download proceeds without
 knowing about all the shares that are out there and currently the
 downloader ignores the information about shares which arrives late.

 Here is a patch in unified diff form which fixes this -- making download
 accept and use information that arrives after "stage 4" of download has
 begun, and also has incomplete changes to the unit tests to
 deterministically exercise this case.

-- 
Ticket URL: <http://allmydata.org/trac/tahoe/ticket/287#comment:16>
tahoe-lafs <http://allmydata.org>
secure decentralized file storage grid


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