= Page Stats Middleware =

Display performance metrics measured during the generation of a page. Allows you to display total time, python time, database time, and number of queries for the rendered page.

== The Python Code ==

{{{
#!python
import re
from operator import add
from time import time
from django.db import connection

class StatsMiddleware(object):

    def process_view(self, request, view_func, view_args, view_kwargs):

        # turn on debugging in db backend to capture time
        from django.conf import settings
        debug = settings.DEBUG
        settings.DEBUG = True

        # get number of db queries before we do anything
        n = len(connection.queries)

        # time the view
        start = time()
        response = view_func(request, *view_args, **view_kwargs)
        totTime = time() - start

        # compute the db time for the queries just run
        queries = len(connection.queries) - n
        if queries:
            dbTime = reduce(add, [float(q['time']) 
                                  for q in connection.queries[n:]])
        else:
            dbTime = 0.0

        # and backout python time
        pyTime = totTime - dbTime

        # restore debugging setting
        settings.DEBUG = debug

        stats = {
            'totTime': totTime,
            'pyTime': pyTime,
            'dbTime': dbTime,
            'queries': queries,
            }

        # replace the comment if found            
        if response and response.content:
            s = response.content
            regexp = re.compile(r'(?P<cmt><!--\s*STATS:(?P<fmt>.*?)-->)')
            match = regexp.search(s)
            if match:
                s = s[:match.start('cmt')] + \
                    match.group('fmt') % stats + \
                    s[match.end('cmt'):]
                response.content = s

        return response
}}}


== The HTML ==

Put a comment in your template in this format:
{{{
<!-- STATS: format_string -->
}}}

Example:
{{{
<!-- STATS: Total: %(totTime).2f Python: %(pyTime).2f DB: %(dbTime).2f Queries: %(queries)d -->
}}}