500 internal server error when importing a python module in wsgi

Question

I've got a Python script that is executing functions asynchronously by using PEST wsgi library. However, when I try to import another module it simply results in a 500 error.

The way I try to reference it is:

from foo import * 
from foo import Foo

where foo is a file .py in which I have the object that I want to reference to.

Tried to monitor the calls through Chrome's Inspect Element Control but couldn't find a thing.

Also tried to debug using Apache's error log, but nothing there.
Any hints appreciated.

Update: I've tried the following which resulted in the same 500 error:

--make use of

import site 

and

site.addsitedir("path/to/my/py/files/folder")

--modify the Apache2 httpd.conf file by inserting the following:

WSGIPythonPath /path/to/my/py/files/folder

--modify the application conf file in /etc/apache2/sites-available/myapp.conf, by inserting the above WSGIPythonPath

Answer 1

Apache's 500 error just tells you that the Python script is returning an error. My guess is that in the Apache environment, Python can't find that module. Try a simple script that prints sys.path and makes sure it has the directories in it you expect.

Answer 2

Adding

WSGIPythonPath /path/to/my/py/files/folder

before any other alias or directory in the application conf file really makes the difference. Problem solved!

Answer 3

Maybe you should use this pattern for cgi scripts to get errors to html form:

import cgi
import cgitb; cgitb.enable()  # for troubleshooting
import traceback
# code here
except:
    tb = traceback.format_exception(sys.exc_type, sys.exc_value, sys.exc_traceback)
    tb = ''.join(tb)
    print '<pre>%s</pre></body></html>' % tb

Answer 4

If an exception propagates back up to mod_wsgi then the details should be logged to appropriate Apache error log. If it isn't, then it may be that the WSGI framework/toolkit you are using is capturing the exception and returning a generic HTTP 500 response page. If that is the case, you may need to enable debug option in that WSGI framework/toolkit being used.

Alternatively, the problem isn't with the WSGI script file/application but with Apache configuration in which case you wouldn't be looking for a Python exception/traceback. You thus need to look more carefully at the Apache error log files and look for any error at all and provide what it says.