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

Fri Sep 30 16:17:04 EDT 2016

That's be interesting. I thought the next release was going to be the
Python 3 (but still supporting 2.7) version?

On Fri, Sep 30, 2016 at 8:24 PM, William Blevins <wblevins001 at gmail.com>
wrote:

> Welcome.
>
> We have several good updates since 2.5.0 available, so I am hoping that we
> can get a few more in (like this issue) and do another release.
>
> V/R,
> William
>
> On Fri, Sep 30, 2016 at 2:58 PM, Shane Gannon <sgannon200 at gmail.com>
> wrote:
>
>> 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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