[tahoe-lafs-trac-stream] [tahoe-lafs] #2101: improve error messages from failed uploads

[tahoe-lafs]

#2101: improve error messages from failed uploads
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 Reporter:  zooko                                |          Owner:  daira
     Type:  defect                               |         Status:  new
 Priority:  normal                               |      Milestone:
Component:  unknown                              |  undecided
 Keywords:  upload error servers-of-happiness    |        Version:  1.10.0
  transparency                                   |  Launchpad Bug:
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 The error message when an upload fails is a "wall of text". It is hard to
 read. It looks like this:


    [Failure instance: Traceback: <class
 'allmydata.interfaces.!UploadUnhappinessError'>: server selection failed
 for <Tahoe2ServerSelector for upload dglev>: shares could be placed or
 found on only 0 server(s). We were asked to place shares on at least 4
 server(s) such that any 3 of them have enough shares to recover the file.
 (placed 0 shares out of 10 total (10 homeless), want to place shares on at
 least 4 servers such that any 3 of them have enough shares to recover the
 file, sent 5 queries to 5 servers, 5 queries asked about existing shares
 (of which 0 failed due to an error), 0 queries placed some shares, 0
 placed none (of which 0 placed none due to the server being full and 0
 placed none due to an error))

 Daira pointed out that even though the current error message is too long,
 it still lacks the most important information that you might want to use
 in your response to this error, which is the identities of which servers
 failed and which succeeded.

 A possible improvement to this would be to return a data structure instead
 of a string, similar to the
 [source:trunk/src/allmydata/check_results.py?annotate=blame&rev=188c7fecf5d2e62d8dcfbff0791fe1125def971b#L7
 CheckResults].

 There is probably a related data structure already being produced and
 displayed over on the "Recent Uploads and Downloads" page for the failed
 upload.

-- 
Ticket URL: <https://tahoe-lafs.org/trac/tahoe-lafs/ticket/2101>
tahoe-lafs <https://tahoe-lafs.org>
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