commonware 0.2.4

A place to keep stuff we want to share, like middleware.

Commonware is a collection of small but useful tools for Django.

They seemed too small to be worth their own packages, but we also wanted to share them. So here they are.

Logging

commonware.log

commonware.log overloads logging to add the IP address of a request to the log. This is accessed in log formats with REMOTE_ADDR.

To use commonware.log, you need to call logging.setLoggerClass() before your first call to logging.getLogger().

For example:

>>> import logging

>>> import commonware.log

>>> logging.setLoggerClass(commonware.log.Logger)

>>> log = logging.getLogger('z')
<commonware.log.Logger>

>>> fmt = '[%(REMOTE_ADDR)s] %(msg)s'

>>> handler = logging.StreamHandler()

>>> formatter = logging.Formatter(fmt)

>>> handler.setFormatter(formatter)

>>> log.addHandler(handler)

Thread-local storage

commonware.log needs to store the IP address of the request in thread- local storage. This requires extra middleware to first store the address before commonware.log can access it.

Fortunately, that’s fairly easy. Just add commonware.log.LogRequestThreadMiddleware to your MIDDLEWARE_CLASSES before any other middleware that uses logging.

If a remote IP address can’t be found, an empty string will be returned instead.

Middleware

NoVarySessionMiddleware

By default, Django likes to send Vary: Cookie if you touch sessions at all. While that’s fine for many users, if your app is behind a load-balancer or reverse proxy, Vary: headers can be painful.

commonware.middleware.NoVarySessionMiddleware prevents Django from adding Vary: Cookie, but protects other Vary: headers.

To use NoVarySessionMiddleware, replace the Django SessionMiddleware with commonware.middleware.NoVarySessionMiddleware in your MIDDLEWARE_CLASSES.

SetRemoteAddrFromForwardedFor

For servers behind reverse-proxies, either load balancers or caches, the value of request.META['REMOTE_ADDR'] is usually wrong: it is usually set to the IP address of the proxy.

commonware.middleware.SetRemoteAddrFromForwardedFor changes the value of request.META['REMOTE_ADDR'] to the first entry in the X-Forwarded-For header.

Only use SetRemoteAddrFromForwardedFor if you know your app is behind well-behaved reverse proxies, as the X-Forwarded-For header is very easy to spoof.