multitenancy.diff

diff --git a/django/contrib/sites/models.py b/django/contrib/sites/models.py
index 879497d..0b78455 100644
--- a/django/contrib/sites/models.py
+++ b/django/contrib/sites/models.py
@@ -33,9 +33,9 @@ class SiteManager(models.Manager):
         project's settings. The ``Site`` object is cached the first
         time it's retrieved from the database.
         """
-        from django.conf import settings
+        from django.core.urlresolvers import get_site
         try:
-            sid = settings.SITE_ID
+            sid = get_site()
         except AttributeError:
             from django.core.exceptions import ImproperlyConfigured
             raise ImproperlyConfigured("You're using the Django \"sites framework\" without having set the SITE_ID setting. Create a site in your database and set the SITE_ID setting to fix this error.")
diff --git a/django/core/handlers/base.py b/django/core/handlers/base.py
index 900ea8e..7abdba8 100644
--- a/django/core/handlers/base.py
+++ b/django/core/handlers/base.py
@@ -82,6 +82,10 @@ class BaseHandler(object):
         urlconf = settings.ROOT_URLCONF
         urlresolvers.set_urlconf(urlconf)
         resolver = urlresolvers.RegexURLResolver(r'^/', urlconf)
+
+        site = getattr(settings, 'SITE_ID', None)
+        urlresolvers.set_site(site)
+
         try:
             response = None
             # Apply request middleware
@@ -97,6 +101,10 @@ class BaseHandler(object):
                     urlresolvers.set_urlconf(urlconf)
                     resolver = urlresolvers.RegexURLResolver(r'^/', urlconf)
 
+                if hasattr(request, 'site'):
+                    site = request.site
+                    urlresolvers.set_site(site)
+
                 resolver_match = resolver.resolve(request.path_info)
                 callback, callback_args, callback_kwargs = resolver_match
                 request.resolver_match = resolver_match
diff --git a/django/core/urlresolvers.py b/django/core/urlresolvers.py
index ffe74bc..975014a 100644
--- a/django/core/urlresolvers.py
+++ b/django/core/urlresolvers.py
@@ -36,6 +36,9 @@ _prefixes = local()
 # Overridden URLconfs for each thread are stored here.
 _urlconfs = local()
 
+# Overridden SITE_ID for each thread are stored here.
+_site = local()
+
 
 class ResolverMatch(object):
     def __init__(self, func, args, kwargs, url_name=None, app_name=None, namespaces=None):
@@ -548,6 +551,16 @@ def get_urlconf(default=None):
     """
     return getattr(_urlconfs, "value", default)
 
+def set_site(site):
+    if site:
+        _site.value = site
+    else:
+        if hasattr(_site, "value"):
+            del _site.value
+
+def get_site(default=None):
+    return getattr(_site, "value", default)
+
 def is_valid_path(path, urlconf=None):
     """
     Returns True if the given path resolves against the default URL resolver,