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Re: [SVNDev] Re: Problems with transaction file "next-ids" on Windows

From: Mathias Weinert <wein_at_mccw.de>
Date: Wed, 03 Aug 2011 16:51:37 +0200

Daniel Shahaf <d.s_at_daniel.shahaf.name> wrote:

> Philip Martin wrote on Wed, Jul 20, 2011 at 15:12:51 +0100:
>> Daniel Shahaf <d.s_at_daniel.shahaf.name> writes:
>>
>> > Mathias Weinert wrote on Wed, Jul 20, 2011 at 14:59:23 +0200:
>> >>
>> >> each time when I am loading a certain dump file on Windows which
>> >> contains one revision with over 100K changed paths I get the error
>> >> "Can't open file
>> >> 'c:\Repositories\test\db\transactions\5445-479.txn\next-ids': The
>> >> requested operation cannot be performed on a file with a user-mapped
>> >> section open.". After looking at the mailing list archives and other
>> >> mailing lists I found out that I am not the only one to encounter
>> >> this problem and that in most cases a virus scanner was the cause of
>> >> the problem. And indeed, adding next-ids to the exclusion list
>> >> solved the problem.
>> >>
>> >> But now I wonder if svnadmin couldn't handle this case a bit more
>> >> elegantly. IMHO it would make sense not to quit the load immediately
>> >> but to try it again maybe after waiting half a second or so if this
>> >> specific error occurs (some other users reported that they got the
>> >> error "The process cannot access the file because it is being used
>> >> by another process."). If we can't access next-ids after trying it
>> >> let's say 5 times with a little pause after each try we still can
>> >> quit the load process.
>> >
>> > It would be good to solve this now as that is one of the concerns with
>> > the (partially implemented) design for revprop packing, due for release
>> > in 1.8.
>>
>> The current implementation writes the file inplace:
>>
>> static svn_error_t *
>> write_next_ids(svn_fs_t *fs,
>> const char *txn_id,
>> const char *node_id,
>> const char *copy_id,
>> apr_pool_t *pool)
>> {
>> apr_file_t *file;
>> svn_stream_t *out_stream;
>>
>> SVN_ERR(svn_io_file_open(&file, path_txn_next_ids(fs, txn_id, pool),
>> APR_WRITE | APR_TRUNCATE,
>> APR_OS_DEFAULT, pool));
>>
>> out_stream = svn_stream_from_aprfile2(file, TRUE, pool);
>>
>> SVN_ERR(svn_stream_printf(out_stream, pool, "%s %s\n", node_id, copy_id));
>>
>> SVN_ERR(svn_stream_close(out_stream));
>> return svn_io_file_close(file, pool);
>> }
>>
>> Is there any reason we don't switch to our standard pattern: write to a
>> temp file and rename? That would give us Subversion's standard retry
>> loop -- would that fix "requested operation cannot be performed"?
>
> fs_fs.c:move_into_file() already does the rename loop, so no objection.
> (assuming we document that the use of move_into_file() is for
> performance and virus scanners rather than for concurrent reader
> correctness)
>

I replaced svn_io_file_open, svn_stream_printf and svn_stream_close
with svn_io_write_unique and move_into_place (see attached patch).
Although this works correctly it shows bad performance. Loading a dump
from a little repo which mainly has a 2000 files commit now takes
about 400s while with the original version it only took about 100s.

Received on 2011-08-03 16:52:11 CEST

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