[Scons-users] Timing Issue with files retrieved from the SCons Cache

Fri Sep 30 14:58:26 EDT 2016

That makes sense. It also means a downgrade should be a viable option.

Thanks William

On Fri, Sep 30, 2016 at 7:11 PM, William Blevins <wblevins001 at gmail.com>
wrote:

> Shane,
>
> Since this is a race condition, then that is expected. SCons 2.5.0 was a
> major feature release. It added support for cross-language dependencies
> which would affect timings on how long files may be open.
>
> V/R,
> William
>
> On Fri, Sep 30, 2016 at 1:56 PM, Shane Gannon <sgannon200 at gmail.com>
> wrote:
>
>> Hi William
>>
>> Sounds like this issue could be related. But I think SCons 2.5.0 may be
>> playing it's part. The 2.3.4 build we have does not hit this problem.
>> Well... at least not with the same level of consistency.
>>
>> Regards
>> Shane
>>
>> On Fri, Sep 30, 2016 at 5:55 PM, William Blevins <wblevins001 at gmail.com>
>> wrote:
>>
>>> Shane,
>>>
>>> This may be specific to Python file handling on Windows and not specific
>>> to SCons 2.5.0. The mail archive is down currently, so I cannot link to the
>>> full article, but here is an excerpt from one of the last conversations.
>>>
>>>
>>> Hi All -
>>>>
>>>
>>>> Our resident Windows expert reached the following conclusions:
>>>>
>>>> Summary: It is a python bug in shutil.copy2
>>>>
>>>> The issue:
>>>> When link.exe opens a obj file, it gets the following error:
>>>> LINK : fatal error LNK1104: cannot open file
>>>> 'build\cached\mongo\tools\mongobridge_options_init.obj'
>>>>
>>>> To diagnose these errors, I enabled ETW tracing with "FileIO stackwalk
>>>> for FileCreate
>>>> <https://msdn.microsoft.com/en-us/library/windows/desktop/aa964768%28v=vs.85%29.aspx>
>>>> +FileCleanup+FileClose"
>>>> <https://msdn.microsoft.com/en-us/library/windows/desktop/aa964773%28v=vs.85%29.aspx> and
>>>> cranked through WPA with the data on Window 2008 R2 & Window 2012 R2. The
>>>> 2012 R2 os offers stack traces which is why I used it
>>>>
>>>> By tracing the build, I can see that link.exe has a call to CreateFile
>>>> fail with
>>>> "A file cannot be opened because the share access flags are
>>>> incompatible. (0xc0000043)"
>>>>
>>>> This occurs because it asked for a file with the following flags "file_open
>>>> synchronous_io_nonalert non_directory_file shareRead", and another
>>>> process had an existing handle to the file"file_overwrite_if
>>>> synchronous_io_nonalert non_directory_file normal shareRead shareWrite".
>>>>
>>>> The existing process that had a handle to the file was none other then
>>>> "python.exe" which created the file originally in copy2, but did not close
>>>> it. I compared normal cases, and it does succesfully close the file. I do
>>>> not know why like 1/100 or 1/200 times it fails.
>>>>
>>>> The workaround is win32file.CopyFile
>>>> <http://timgolden.me.uk/python/win32_how_do_i/copy-a-file.html>.
>>>>
>>>> I patched FS.py with and it worked fine
>>>> win32file.CopyFile(src, dst, 1)
>>>>         return True
>>>>
>>>>
>>>> I can confirm that the issue no-longer reproduces for me with the
>>>> following change to FS.py:
>>>>
>>>> https://github.com/tychoish/mongo/commit/c8450fb4d304b2de06b
>>>> a968b71f6efacd3b5214e
>>>>
>>>> While I'd love to follow this deeper, debugging python's file system
>>>> internals on Windows is not something I can really invest time in right
>>>> now. We are most likely just going to make the above patch to our vendored
>>>> copy of SCons and continue.
>>>>
>>>> Perhaps someone with more Python expertise would be interested in
>>>> pursuing this further? I can give very detailed reproduction instructions.
>>>>
>>>> Thanks,
>>>> Andrew
>>>>
>>>
>>> I do not think this has been officially patched in the development trunk
>>> yet, but it is a known issue.
>>>
>>> V/R,
>>> William
>>>
>>>
>>> On Fri, Sep 30, 2016 at 12:16 PM, Shane Gannon <sgannon200 at gmail.com>
>>> wrote:
>>>
>>>> Hi
>>>>
>>>> I'm hitting a problem with the SCons Cache. Intermiddently (but too
>>>> frequently) a build fails with an error like
>>>>
>>>> *Elapsed Time*
>>>>
>>>> *00:06:43.214* scons: building `out\windows-x86-MD-unicode-vs2015-rel\obj-static\components\memorymanager\tests\unit_tests\TestMemoryManager.obj' because it doesn't exist*00:06:43.215* Retrieved `out\windows-x86-MD-unicode-vs2015-rel\obj-static\components\memorymanager\tests\unit_tests\TestMemoryManager.obj' from cache
>>>>
>>>>
>>>> *00:06:45.660* scons: building `src\jabber-client\jabber-build\Win32\bin\Release\memorymanager-unit-tests.exe' because it doesn't exist*00:06:45.661* LINK src\jabber-client\jabber-build\Win32\bin\Release\memorymanager-unit-tests.exe
>>>>
>>>> *00:06:45.694* LINK : fatal error LNK1104: cannot open file 'out\windows-x86-MD-unicode-vs2015-rel\obj-static\components\memorymanager\tests\unit_tests\TestMemoryManager.obj'
>>>>
>>>>
>>>> It's not specific to .obj files. It can happen for generated .h files,
>>>> .libs, etc. Basically any file retrievable from the cache.
>>>>
>>>> This only occurs on a new build we're working to support. Namely an
>>>> upgrade to Visual Studio 2015 where SCons 2.5.0 is used (versus 2.3.4 on
>>>> the other machines).
>>>>
>>>> I noticed in the Release Notes the following entries for 2.5.0.
>>>>
>>>>     - SCons handles cache directories a bit differently/
>>>>       - Cache files are now stored in 256 subdirectories in the cache directory by
>>>>         default (this stresses NFS less). Existing cache directories will remain as
>>>>         current, but SCons will prompt you to run scons-configure-cache which will
>>>>         allow you to migrate to the new layout, or confirm you want to use the
>>>>         existing layout.
>>>>
>>>>     - New external tool scons-configurecache which allows some configuration of
>>>>       how files in the cache are controlled.
>>>>
>>>> I assume this might be causing the problem. Has anyone else reported an
>>>> issue?
>>>>
>>>> Does anyone have a suggestion on how I can resolve or diagnois it?
>>>>
>>>> PS: We use Windows 10 on our build machines.
>>>>
>>>> Regards
>>>> Shane
>>>>
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>>>>
>>>>
>>>
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