matplotlib-users Mailing List for matplotlib

[Oops... just realised I have been replying to Michael, not the list.
Very sorry.]
I had a closer look at the trace and the ft2font code, and I'm still
none the wiser. It's clear what's happening, I just have no idea why.
 I have tried to trigger it in a test-case by calling imp.load_dynamic
on ft2font repeatedly, and using both threads and processes (which I
didn't think would work, but I was clutching at straws) as well, but
still no joy.
I had a brief look at the python source too (importdl.c and import.c),
which does cache the module objects but admittedly doesn't do locking
that I can see.
This has all been working on the assumption that it is indeed a race
condition of some sort, and if that were the case I'm _also_ unsure
where that could arise from. We are now running on a 24 core machine
(up from 8 on the previous server which had no problems), but my
understanding of what memory is shared where in which
apache/mod_python/wsgi configuration is too fuzzy to make sense of
that possibility. (also, recall that the stack trace was captured
from apache in single-threaded debug mode!)
My current plan to fix it is to push the offending imports from module
top-level down into the functions where they are required, but even
assuming that is successful I would dearly love closure on this!
/Mark.
On 19 May 2011 12:24, Mark Hepburn <mar...@gm...> wrote:
> I spoke too soon, I hit one! (I am unreasonably excited by this at this
> stage). It looks like it's the same issue; it's in FT2Image and arises from
> check_unique_method_name -- I'm about to look through the source, but it
> seems a likely candidate.
> The output of both bt and bt full is attached.
> Thanks once again.
> /Mark.
>
> On 19 May 2011 12:15, Mark Hepburn <mar...@gm...> wrote:
>>
>> Hi, thanks for the reply.
>> I haven't managed to extract one yet; any hints? I've tried a few times
>> with "gdb httpd" -> run -X, but unsuccessfully so far. My understanding is
>> that this runs apache in single-threaded mode, and if it is a threading
>> problem it is unlikely to reproduce the problem (I think). (The other
>> complicating factor is that this is the only server it has been a problem
>> on... which is also the production server, so I've been loathe to slow it
>> down too much like this. Biting the bullet now, though..)
>> There's no stack trace in the apache error log either; in fact there's not
>> even a time-stamp when it crashes, just the message from the subject.
>> Thanks again, Mark.
>>
On 19 May 2011 00:55, Michael Droettboom <md...@st...> wrote:
> Can you provide a stack trace -- either a Python one, or a gdb one?
>
> Mike
>
> On 05/18/2011 03:25 AM, Mark Hepburn wrote:
>> Hi,
>>
>> I have a web application using matplotlib which is unpredictably
>> crashing with the error message from the subject. It seems to be
>> happening in ft2font, but I can't be certain at this stage that it's
>> only occurring there (although since isolating it via logging
>> statements, every time it has occurred has been in that spot). The
>> crash occurs at load time, seemingly through a chain of import
>> statements (starting with wsgi app -> django -> my app):
>> matplotlib.colorbar -> matplotlib.lines -> matplotlib.font_manager ->
>> matplotlib.ft2font
>>
>> Google is strangely quiet on that particular message; the closest I
>> have found that also involves ft2font was this rather old one:
>> http://comments.gmane.org/gmane.comp.python.matplotlib.devel/1332
>>
>> The unpredictable nature of it suggests that it's thread-related, but
>> other than that I have no further clues. The unpredictable nature of
>> the crashes obviously makes testing any theory or avenue quite slow at
>> times! Does anyone have any suggestions, hints for further
>> probing,... anything, please?
>>
>> The particulars:
>> Server OS: openSUSE 11.3 (x86_64)
>> matplotlib: 1.0.0 (compiled from source distro)
>> Server: apache prefork, mod_wsgi
>> Python version: 2.6.4
>>
>> Extra factors:
>> There are two versions of the application, deployed in virtualenvs
>> (identical matplotlib versions). It does affect both of them,
>> although I've only been investigating with one. It frequently seems
>> to affect a group of processes; that is, reloading is required
>> multiple times before it returns to normal.
>>
>> mod_wsgi is running in embedded mode, but the same problem was
>> occurring with mod_python -- that was my main impetus for porting to
>> wsgi in fact. The same application ran fine on the previous server
>> however (SUSE Linux Enterprise Server 11 (x86_64)), in fact with 3
>> versions of the application, using mod_python. It was previously
>> using matplotlib 0.98.5.2; according to my commit message the upgrade
>> was prompted by the server move and that version not compiling against
>> libpng1.4 on the new server.
>>
>> Thanks, Mark.
>>
>>
>
>
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-- 
Where the hell is Mark:
http://blog.everythingtastesbetterwithchilli.com/

There's a heap of searches - the old.nabble one listed.
http://old.nabble.com/matplotlib---users-f2906.html
plus
http://www.mail-archive.com/mat...@li.../info.html
http://blog.gmane.org/gmane.comp.python.matplotlib.general
http://www.mailinglistarchive.com/html/mat...@li.../
I find google to be better at figuring out what you want though. So a 
google search like:
<search terms> site:old.nabble.com intitle:matplotlib intitle:users
tends to work better.
Gerald.
On 18/05/2011 10:55 PM, Benjamin Root wrote:
>
>
> On Wed, May 18, 2011 at 5:52 AM, Yue Chao <cha...@gm... 
> <mailto:cha...@gm...>> wrote:
>
> Thank you Mark!
>
> If there is no search engine, we'll not make full use of FAQ
> history...
>
> Chao
>
>
> There is a search feature provided by nabble here:
>
> http://old.nabble.com/matplotlib---users-f2906.html
>
> Don't know how good it is, but it does exist.
>
> Ben Root
>
>
> ------------------------------------------------------------------------------
> What Every C/C++ and Fortran developer Should Know!
> Read this article and learn how Intel has extended the reach of its
> next-generation tools to help Windows* and Linux* C/C++ and Fortran
> developers boost performance applications - including clusters.
> http://p.sf.net/sfu/intel-dev2devmay
>
>
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> Mat...@li...
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