[tahoe-lafs-trac-stream] [Tahoe-LAFS] #2285: multi backup error

[Tahoe-LAFS]

#2285: multi backup error
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     Reporter:  dawuud   |      Owner:  daira
         Type:  defect   |     Status:  new
     Priority:  normal   |  Milestone:  undecided
    Component:  unknown  |    Version:  1.10.0
   Resolution:           |   Keywords:
Launchpad Bug:           |
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Comment (by zooko):

 I'll bet we could fix this simply by setting
 [https://www.sqlite.org/pragma.html#pragma_busy_timeout PRAGMA
 busy_timeout] to a large value (like 3000 milliseconds). This would, if I
 understand correctly, cause the second one of the `tahoe backup` processes
 that attempted to write to a table to block until the first one finished
 its write and committed the transaction. This would only take a tiny
 fraction of a second (especially if we turned on `journal_mode="WAL"` and
 `synchronous="NORMAL"`, like we do [https://github.com/tahoe-lafs/tahoe-
 lafs/blame/006a04976eb42f56c118c34adf2ddb54c1605edb/src/allmydata/storage/leasedb.py#L130
 in the leasedb branch]).

 The only question I have is: how would we ''test'' a patch which made this
 change!

--
Ticket URL: <https://tahoe-lafs.org/trac/tahoe-lafs/ticket/2285#comment:3>
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