Python (WSGI): Get peak memory usage of each request

Question

I'm using WSGI Daemon process for my Python application, I'm having a problem trying to get the memory usage of each request using the resource module.

It will work as I want it to if using CGI, but with WSGI, the memory usage count gets shared between requests. I believe this has something to do with threading as WSGI spawns processes & threads unlike when using CGI which just spawns a new process for each request.

Here is a minimal example of a WSGI Python application to get peak memory usage of example.com/a and example.com/b:

def application(environ, start_response):

    if environ['REQUEST_URI'] == '/a':
        pass

    elif environ['REQUEST_URI'] == '/b':

        # Use lots of memory
        x = ''
        for _i in range(0, 30000):
            x += ('aaaaaaaaaaaaaaaaaaaaaaaaaaaaqaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'
                  'aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'
                  'aaaaaaaaaaaaawaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'
                  'aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'
                  'aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'
                  'aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'
                  'aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'
                  'aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'
                  'aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'
                  'aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa')

    # Show peak memory used
    # https://stackoverflow.com/questions/938733/total-memory-used-by-python-process#answer-7669482
    import resource
    mem = resource.getrusage(resource.RUSAGE_SELF).ru_maxrss
    content = str(mem)

    status = '200 OK'
    header = [('Content-type', 'text/html; charset=utf-8')]
    start_response(status, header)
    content = content.encode('utf-8')
    return [content]

If I visit example.com/a the memory usage will show ~30008
If I visit example.com/b the memory usage will show ~47984
But if I visit example.com/a again (after visiting example.com/b), it will show ~47984 instead of ~3008.

What I want to happen for the above code is:
example.com/a to always show ~30008
example.com/b to always show ~47984

Any help is much appreciated.