On 18 May 2010 11:06, svanheulen <[email protected]> wrote:
> I'm trying to use matplotlib with mod_wsgi. I'm getting 500 errors the
> first time the page loads but it displays correctly if you refresh the
> page immediately. If I then wait for a while and refresh again it
> gives a 500 error again. Seems like it has something to do with the
> way mod_wsgi loads things. Any ideas?
Looks like a circular import problem in matplotlib.
Try adding as first import, before other matplotlib imports:
import matplotlib
import matplotlib.cbook
See if that even works.
> Here are the versions I'm using:
>
> Apache 2.2.14 (worker MPM)
> mod_wsgi 2.8
> Python 2.6.5
> matplotlib 0.99.1.2
>
> Here is the error that occurs in my Apache logs:
>
> mod_wsgi (pid=1530): Target WSGI script '/home/user/graph.wsgi' cannot
> be loaded as Python module.
> mod_wsgi (pid=1530): Exception occurred processing WSGI script '/home/
> user/graph.wsgi'.
> Traceback (most recent call last):
> File "/home/user/graph.wsgi", line 6, in <module>
> from matplotlib.backends.backend_agg import FigureCanvasAgg
> File "/usr/lib/pymodules/python2.6/matplotlib/backends/
> backend_agg.py", line 28, in <module>
> from matplotlib.backend_bases import RendererBase,\\
> File "/usr/lib/pymodules/python2.6/matplotlib/backend_bases.py",
> line 29, in <module>
> import matplotlib.cbook as cbook
> AttributeError: 'module' object has no attribute 'cbook'
>
> Here is the source of graph.wsgi:
>
> import os
> os.environ['HOME'] = '/tmp'
Setting HOME like that is not a good idea.
Suggest you use WSGIDaemonProcess/WSGIProcessGroup (ie., daemon mode)
and specific user/group options to WSGIDaemonProcess to designate
daemon process to run as a user different to Apache user which has an
actual home directory.
This will solve Python egg cache issues along with other things as well.
Graham
> import StringIO
> from matplotlib.backends.backend_agg import FigureCanvasAgg
> from matplotlib.figure import Figure
>
> def application(environ, start_response):
> output = StringIO.StringIO()
> fig = Figure()
> canvas = FigureCanvasAgg(fig)
> ax = fig.add_subplot(111)
> ax.plot(range(5), range(5))
> canvas.print_figure(output)
> start_response('200 OK', [('Content-type', 'image/png'), ('Content-
> Length', str(output.tell()))])
> return [output.getvalue()]
>
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