[tahoe-lafs-trac-stream] [tahoe-lafs] #1865: backup has over-general exception swallowing that leads to assertion failures.

[tahoe-lafs]

#1865: backup has over-general exception swallowing that leads to assertion
failures.
--------------------------+--------------------------------
     Reporter:  nejucomo  |      Owner:  davidsarah
         Type:  defect    |     Status:  new
     Priority:  normal    |  Milestone:  undecided
    Component:  unknown   |    Version:  1.9.2
   Resolution:            |   Keywords:  error tahoe-backup
Launchpad Bug:            |
--------------------------+--------------------------------

Comment (by zooko):

 Here's a patch which I think will do the right thing while not catching
 exceptions that it shouldn't catch. This is safe in sqlite, because sqlite
 always locks whole tables. For databases with finer-grained transactions,
 it would be necessary to use isolation level "serializable" or stricter
 for this to be safe.

 {{{
 diff --git a/src/allmydata/scripts/backupdb.py
 b/src/allmydata/scripts/backupdb.py
 index 75ee0d9..8eed692 100644
 --- a/src/allmydata/scripts/backupdb.py
 +++ b/src/allmydata/scripts/backupdb.py
 @@ -247,14 +247,12 @@ class BackupDB_v2:
          # sqlite has "INSERT ON CONFLICT REPLACE", but not mysql
          # So we use INSERT, ignore any error, then a SELECT
          c = self.cursor
 -        try:
 -            c.execute("INSERT INTO caps (filecap) VALUES (?)",
 (filecap,))
 -        except (self.sqlite_module.IntegrityError,
 self.sqlite_module.OperationalError):
 -            # sqlite3 on sid gives IntegrityError
 -            # pysqlite2 (which we don't use, so maybe no longer relevant)
 on dapper gives OperationalError
 -            pass
          c.execute("SELECT fileid FROM caps WHERE filecap=?", (filecap,))
          foundrow = c.fetchone()
 +        if foundrow is None:
 +            c.execute("INSERT INTO caps (filecap) VALUES (?)",
 (filecap,))
 +            c.execute("SELECT fileid FROM caps WHERE filecap=?",
 (filecap,))
 +            foundrow = c.fetchone()
          assert foundrow
          fileid = foundrow[0]
          return fileid
 }}}

-- 
Ticket URL: <https://tahoe-lafs.org/trac/tahoe-lafs/ticket/1865#comment:1>
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