[tahoe-lafs-trac-stream] [tahoe-lafs] #1835: stop grovelling the whole storage backend looking for externally-added shares to add a lease to

[tahoe-lafs]

#1835: stop grovelling the whole storage backend looking for externally-added
shares to add a lease to
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     Reporter:  zooko    |      Owner:
         Type:           |     Status:  new
  enhancement            |  Milestone:  undecided
     Priority:  normal   |    Version:  1.9.2
    Component:  code-    |   Keywords:  leases garbage-collection
  storage                |  accounting
   Resolution:           |
Launchpad Bug:           |
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Comment (by zooko):

 Very good points, David-Sarah. I agree with everything you said in
 comment:1. I hadn't thought of the option of treating the leasedb as
 authoritative, but now that you mentioned it, I like that option because
 it is very efficient. Especially in the cloud-backend case where querying
 the leasedb is a purely local, synchronous, very fast, and zero-dollar-
 cost operation, but querying the storage backend is asynchronous (which
 complicates code), slow, and might even have a (very small) monetary cost.

 Unfortunately, if we ''did'' treat the leasedb as authoritative for the
 existence of a share, then the approach — which I like after reading your
 comment:1 — would not work: using a filecheck through the storage server's
 foolscap interface as the way to alert the server to the existence of an
 externally-imported share.

 Hrm… ☹

 I kind of think it might be worth it, to get the improved efficiency and
 performance of relying on the leasedb as the authority for share
 existence, to separate a LAFS client saying "Please let me know if you
 have this share!" from a server operator saying "I know more than you know
 about this: go look and you might find out that you have this share now!".

-- 
Ticket URL: <https://tahoe-lafs.org/trac/tahoe-lafs/ticket/1835#comment:2>
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