deepakprakash · December 11, 2015 11:49 · Dec 11, 2015 · Jul 18, 2014
diff --git a/Django MultiDB selection from URL → middleware.py b/Django MultiDB selection from URL → middleware.py
diff --git a/Django MultiDB selection from URL b/Django MultiDB selection from URL
@@ -0,0 +1,85 @@
+"""
+Select database based on URL variable
+
+Inspired by this Django snipped:
+
+https://djangosnippets.org/snippets/2037/
+
+It's assumed that any view in the system with a cfg keyword argument passed to
+it from the urlconf may be routed to a separate database. for example:
+
+  url( r'^(?P<db>\w+)/account/$', 'views.account' )
+
+The middleware and router will select a database whose alias is <db>,
+"default" if no db argument is given and raise a 404 exception if not listed in
+settings.DATABASES, all completely transparent to the view itself.
+"""
+import threading
+from django.http import Http404
+
+request_cfg = threading.local()
+
+
+class MultiDbRouterMiddleware(object):
+    """
+    The Multidb router middelware.
+
+    he middleware process_view (or process_request) function sets some context
+    from the URL into thread local storage, and process_response deletes it. In
+    between, any database operation will call the router, which checks for this
+    context and returns an appropriate database alias.
+
+    Add this to your middleware, for example:
+
+    MIDDLEWARE_CLASSES += ['bananaproject.multidb.MultiDbRouterMiddleware']
+    """
+    def process_view(self, request, view_func, args, kwargs):
+        if 'db' in kwargs:
+            request_cfg.db = kwargs['db']
+            request.SELECTED_DATABASE = request_cfg.db
+
+    def process_response(self, request, response):
+        if hasattr(request_cfg, 'db'):
+            del request_cfg.db
+        return response
+
+
+class MultiDbRouter(object):
+    """
+    The multiple database router.
+
+    Add this to your Django database router configuration, for example:
+
+    DATABASE_ROUTERS += ['bananaproject.multidb.MultiDbRouter']
+    """
+    def _multi_db(self):
+        from django.conf import settings
+        if hasattr(request_cfg, 'db'):
+            if request_cfg.db in settings.DATABASES:
+                return request_cfg.db
+            else:
+                raise Http404
+        else:
+            return 'default'
+
+    def db_for_read(self, model, **hints):
+        if model._meta.app_label != 'banana':
+            return 'default'
+        return self._multi_db()
+
+    db_for_write = db_for_read
+
+
+def multidb_context_processor(request):
+    """
+    This context processor will add a db_name to the request.
+
+    Add this to your Django context processors, for example:
+
+    TEMPLATE_CONTEXT_PROCESSORS +=[
+        'bananaproject.multidb.multidb_context_processor']
+    """
+    if hasattr(request, 'SELECTED_DATABASE'):
+        return {'db_name': request.SELECTED_DATABASE}
+    else:
+        return {}
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