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DebugFooter middleware

Author:
simon
Posted:
May 21, 2008
Language:
Python
Version:
.96
Score:
18 (after 18 ratings)

Adds a hidden footer to the bottom of every text/html page containing a list of SQL queries executed and templates that were loaded (including their full filesystem path to help debug complex template loading scenarios).

To use, drop in to a file called 'debug_middleware.py' on your Python path and add 'debug_middleware.DebugFooter' to your MIDDLEWARE_CLASSES setting.

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import time
from django.dispatch import dispatcher
from django.core.signals import request_started
from django.test.signals import template_rendered
from django.conf import settings
from django.db import connection
from django.utils.encoding import force_unicode

TEMPLATE = """
<div id="debug" style="clear:both;">
<a href="#debugbox"
    onclick="this.style.display = 'none';   
        document.getElementById('debugbox').style.display = 'block';
        return false;"
    style="font-size: small; color: red; text-decoration: none; display: block; margin: 12px;"
>+</a>

<div style="display: none;clear: both; border: 1px solid red; padding: 12px; margin: 12px; overflow: scroll" id="debugbox">

<p>Server-time taken: {{ server_time|floatformat:"5" }} seconds</p>
<p>Templates used:</p>
{% if templates %}
<ol>
    {% for template in templates %}
        <li><strong>{{ template.0 }}</strong> loaded from <samp>{{ template.1 }}</samp></li>
    {% endfor %}
</ol>
{% else %}
    None
{% endif %}
<p>Template path:</p> 
{% if template_dirs %}
    <ol>
    {% for template in template_dirs %}
        <li>{{ template }}</li>
    {% endfor %}
    </ol>
{% else %}
    None
{% endif %}
<p>SQL executed:</p>
{% if sql %}
<ol>
{% for query in sql %}
    <li><pre>{{ query.sql|linebreaksbr }}</pre><p>took {{ query.time|floatformat:"3" }} seconds</p></li>
{% endfor %}
</ol>
<p>Total SQL time: {{ sql_total }}</p>
{% else %}
    None
{% endif %}
</div>
</div>
</body>
"""

# Monkeypatch instrumented test renderer from django.test.utils - we could use
# django.test.utils.setup_test_environment for this but that would also set up
# e-mail interception, which we don't want
from django.test.utils import instrumented_test_render
from django.template import Template, Context
if Template.render != instrumented_test_render:
    Template.original_render = Template.render
    Template.render = instrumented_test_render
# MONSTER monkey-patch
old_template_init = Template.__init__
def new_template_init(self, template_string, origin=None, name='<Unknown Template>'):
    old_template_init(self, template_string, origin, name)
    self.origin = origin
Template.__init__ = new_template_init

class DebugFooter:
    def process_request(self, request):
        self.time_started = time.time()
        self.templates_used = []
        self.contexts_used = []
        self.sql_offset_start = len(connection.queries)
        dispatcher.connect(
            self._storeRenderedTemplates, signal=template_rendered
        )
        
    def process_response(self, request, response):
        # Only include debug info for text/html pages not accessed via Ajax
        if 'text/html' not in response['Content-Type']:
            return response
        if request.is_ajax():
            return response
        if not settings.DEBUG:
            return response
        if response.status_code != 200:
            return response
        
        templates = [
            (t.name, t.origin and t.origin.name or 'No origin')
            for t in self.templates_used
        ]
        sql_queries = connection.queries[self.sql_offset_start:]
        # Reformat sql queries a bit
        sql_total = 0.0
        for query in sql_queries:
            query['sql'] = reformat_sql(query['sql'])
            sql_total += float(query['time'])
        
        #import pdb; pdb.set_trace()
        
        
        debug_content = Template(TEMPLATE).render(Context({
            'server_time': time.time() - self.time_started,
            'templates': templates,
            'sql': sql_queries,
            'sql_total': sql_total,
            'template_dirs': settings.TEMPLATE_DIRS,
        }))
        
        content = response.content
        response.content = force_unicode(content).replace('</body>', debug_content)
        
        #import pdb; pdb.set_trace()
        return response
    
    def _storeRenderedTemplates(self, signal, sender, template, context):
        self.templates_used.append(template)
        self.contexts_used.append(context)

def reformat_sql(sql):
    sql = sql.replace('`,`', '`, `')
    sql = sql.replace('` FROM `', '` \n  FROM `')
    sql = sql.replace('` WHERE ', '` \n  WHERE ')
    sql = sql.replace(' ORDER BY ', ' \n  ORDER BY ')
    return sql

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Comments

munhitsu (on May 21, 2008):

thanks - fantastic usability

#

kayamb (on May 21, 2008):

Fantastic snippet! However, it does not work with ajax requests, so here's the changes I've done:

  • Remove "</body>" from the template definition.
  • Remove the "if request.is_ajax(): return response" statements.
  • Replace the bottom of the process_response method with:
    if content.lower().count('`</body>`') > 0:
    response.content = force_unicode(content).replace('`</body>`', debug_content) + '`</body>`'
else:
    response.content = force_unicode(content) + debug_content

#

mixtline (on May 23, 2008):
  1. use "if request.META.get('HTTP_X_REQUESTED_WITH') == 'XMLHttpRequest'" instead of "if request.is_ajax()"
  2. use

import re

p = re.compile('<\/body>', re.IGNORECASE)

response.content = p.sub(debug_content, force_unicode(content))

instead of line #128

#

crucialfelix (on July 7, 2008):

excellent. is there anyway to also know what view was executed ?

#

peterbe (on September 3, 2008):

This snippet has stopped working as of latest development version. Last line of the error is:

AttributeError: 'module' object has no attribute 'connect'

I can provide a full traceback if necessary. (I'm using mysql and revision 8922)

#

aaron08544 (on September 27, 2008):

If you don't care about the TextMate links, you can replace line 78: old: dispatcher.connect( self._storeRenderedTemplates, signal=template_rendered ) new: template_rendered.connect(self._storeRenderedTemplates)

and change the _storeRenderedTemplates function to

def _storeRenderedTemplates(self, **kwargs):
    #signal=signal, sender=sender, template=template, context=context):
    template = kwargs.get('template')
    if(template):
        self.templates_used.append(template)
    context = kwargs.get('context')
    if(context):
        self.contexts_used.append(context)

This is just a diff from 1033.

#

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