This change looks good to me.  Nice work.

On Aug 11, 2011, at 10:37 AM, David Hess wrote:

> We have servers that deal with power outages (and dirty power in general) and
have ended up with some corrupted durus databases. We've used the normal
"repair" feature to handle a lot of the cases but we have another that's
occurring on occasion that is not handled by repair. It is failing as this
exception:
>
> Traceback (most recent call last):
>  File "/usr/local/bin/durus", line 22, in 
>    client_main()
>  File "/usr/local/lib/python2.6/dist-packages/durus/client.py", line 108, in
client_main
>    options.startup)
>  File "/usr/local/lib/python2.6/dist-packages/durus/client.py", line 35, in
interactive_client
>    storage = FileStorage(file, readonly=readonly, repair=repair)
>  File "/usr/local/lib/python2.6/dist-packages/durus/file_storage.py", line 73,
in __init__
>    self.shelf = Shelf(filename, readonly=readonly, repair=repair)
>  File "/usr/local/lib/python2.6/dist-packages/durus/shelf.py", line 91, in
__init__
>    self.file, repair=repair)
>  File "/usr/local/lib/python2.6/dist-packages/durus/shelf.py", line 296, in
read_transaction_offsets
>    file.seek(position + 8 + record_length)
>  File "/usr/local/lib/python2.6/dist-packages/durus/file.py", line 41, in seek
>    self.file.seek(n, whence)
> IOError: [Errno 22] Invalid argument
>
> We've come up with the following patch:
>
> --- /usr/local/lib/python2.6/dist-packages/durus/shelf.py     2007-04-24
16:10:16.000000000 -0500
> +++ durus/shelf.py    2011-08-11 08:18:51.169288642 -0500
> @@ -297,18 +297,17 @@
>         if file.tell() != transaction_end:
>             raise ShortRead
>         return transaction_offsets
> -    except ShortRead, e:
> +    except (ShortRead, IOError), e:
>         position = file.tell()
>         if position > transaction_start:
>             if repair:
>                 file.seek(transaction_start)
>                 file.truncate()
>             else:
> -                e.args = repr(dict(
> +                raise ShortRead(repr(dict(
>                     transaction_start=transaction_start,
>                     transaction_end = transaction_end,
> -                    position=position))
> -                raise
> +                    position=position)))
>         return None
>
> Or test database started out as:
>
> -rw-r--r--  1 fishfinder fishfinder 49371713 2011-08-10 14:12 db.durus
>
> We ran with this patch and without the repair switch and got the following
(expected) report:
>
> durus.utils.ShortRead: {'position': 47501336L, 'transaction_start': 47501312L,
'transaction_end': 12061693972974895416L}
>
> We then ran again with --repair and the database was able to be opened. The
resulting database looked like this:
>
> -rw-r--r--  1 fishfinder fishfinder 47501312 2011-08-11 08:14 db.durus
>
> Can anybody comment on whether this patch makes the appropriate sense and is
safe enough? We (fortunately!) have a limited number of corrupted databases to
try this on.
>
> Thanks.
>
> Dave
>
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