pandas and numpy thread safety
see caveat in the docs here: http://pandas.pydata.org/pandas-docs/dev/gotchas.html#thread-safety
pandas is not thread safe because the underlying copy mechanism is not. Numpy I believe has an atomic copy operation, but pandas has a layer above this.
Copy is the basis of pandas operations (as most operations generate a new object to return to the user)
It is not trivial to fix this and would come with a pretty heavy perf cost so would need a bit of work to deal with this properly.
Easiest is simply not to share objects across threads or lock them on usage.
Configure mod_wsgi to run in a single thread mode.
WSGIDaemonProcess mysite processes=5 threads=1WSGIProcessGroup mysiteWSGIApplicationGroup %{GLOBAL}In this case it is using mod_wsgi daemon mode so that processes/threads can be set independently on whatever Apache MPM you are using.