Potential thread safety issues

[martinbertolino]

We have noticed that this middleware is randomly logging empty bodies for certain requests in our PROD environment. After doing some research and code reviews, I believe that there is a potential problem with the following members of the LoggingMiddleware class:

    self.boundary = ""
    self.cached_request_body = None

These two member can get mutated on a per call basis, however in a multi-threaded environment, they could be overwritten by a different thread before they are used for the current invocation.

The reason for this statement are the following sources:

https://blog.roseman.org.uk/2010/02/01/middleware-post-processing-django-gotcha/
https://stackguides.com/questions/10763641/is-this-django-middleware-thread-safe
https://stackoverflow.com/questions/6214509/is-django-middleware-thread-safe

I also did some testing on our code, and I have noticed that the middleware is sort of a 'singleton' that gets constructed only once per process and reused for all threads, which would explain the random empty bodies in our logs as the cached_request_body reference could be overwritten by a different thread.

I would be happy to craft and propose a solution and create a PR for it, but I have not seen much activity on this project so I want to check if it is still being maintained.

Let me know and I will propose a PR.

Thank you.

[famousfilm]

@martinbertolino Thanks for noticing. Yes, feel free to put up an PR and ping me. I'll take a look.

[martinbertolino]

@famousfilm PR has been created.

#143

[famousfilm]

Fixed by #143