Know your namespace
A peek inside a django namespace.
(and an open source project implementation: django-db-log)

django.middleware

Pluggable

why do i care?
simple dummy...

available middleware provides:
• session handling • internationalization
• caching • db transactions
• authentication • gzip compression
• flat pages • etc.

...umm, yea i could use those.

activating middleware
MIDDLEWARE_CLASSES = (
'django.middleware.common.CommonMiddleware',
'django.contrib.sessions.middleware.SessionMiddleware',
'django.contrib.auth.middleware.AuthenticationMiddleware',
'django.middleware.doc.XViewMiddleware',
)

need a custom solution?

easy as pie

Simple Guidelines
• don’t have to subclass anything
• live anywhere on the python path
(reusable!)
• must define one or more of these 4
methods...

feeling the flow, being the ball
process process process
call view
request view response
exception?
process
exception

Real World Example

from models import Error, ErrorBatch
import traceback
import socket
import warnings
Look mom, no hands!
import md5
class DBLogMiddleware(object):
def process_exception(self, request, exception):
server_name = socket.gethostname()
tb_text = traceback.format_exc()
class_name = exception.__class__.__name__
checksum = md5.new(tb_text).hexdigest()
defaults = dict(
class_name = class_name,
message = exception.message,
url = request.build_absolute_uri(),
server_name = server_name,
traceback = tb_text,
)
try:
Error.objects.create(**defaults)
batch, created = ErrorBatch.objects.get_or_create(
class_name = class_name,
server_name = server_name,
checksum = checksum,
defaults = defaults
)
if not created:
batch.times_seen += 1
batch.save()
except Exception, exc:
warnings.warn(unicode(exc))

Discussion
• http://code.google.com/p/django-db-log/
• http://www.davidcramer.net/
• http://www.djangoproject.com/documentation/middleware/