Adjust settings to use new pinning database router and middleware.

Audit forum views for master-slave race conditions. Added a few comments about possible ones but didn't find any that can't be equally caused by our autocommitting.

apps/forums/views.py

@@ -104,6 +104,11 @@ def reply(request, forum_slug, thread_id):
     if form.is_valid():
         forum = get_object_or_404(Forum, slug=forum_slug)
         thread = get_object_or_404(Thread, pk=thread_id, forum=forum)
+
+        # A reply or two might sneak in after the thread is locked due to
+        # replication lag, but that should be very rare and won't result in a
+        # user-visible error. Not worth pinning to master as long as we're not
+        # even using one transaction per request.
         if not thread.is_locked:
             reply_ = form.save(commit=False)
             reply_.thread = thread
@@ -167,6 +172,9 @@ def lock_thread(request, forum_slug, thread_id):
                             (Forum, 'slug__iexact', 'forum_slug'))
 def sticky_thread(request, forum_slug, thread_id):
     """Mark/unmark a thread sticky."""
+    # TODO: Have a separate sticky_thread() and unsticky_thread() to avoid a
+    # race condition where a double-bounce on the "sticky" button sets it
+    # sticky and then unsticky. [572836]
 
     forum = get_object_or_404(Forum, slug=forum_slug)
     thread = get_object_or_404(Thread, pk=thread_id, forum=forum)
@@ -302,7 +310,10 @@ def delete_post(request, forum_slug, thread_id, post_id):
 @login_required
 @require_POST
 def watch_thread(request, forum_slug, thread_id):
-    """Start watching a thread."""
+    """Toggle whether a thread is being watched."""
+    # TODO: Have a separate watch_thread() and unwatch_thread() to avoid a
+    # race condition where a double-bounce on the "watch" button watches and
+    # then unwatches a thread. [572836]
 
     forum = get_object_or_404(Forum, slug=forum_slug)
     thread = get_object_or_404(Thread, pk=thread_id, forum=forum)

requirements.txt

@@ -1,5 +1,5 @@
 -e svn+http://code.djangoproject.com/svn/django/trunk@13302#egg=Django
--e git://github.com/jbalogh/django-multidb-router.git@8eeef712a2f594d9fe6ba1e2ffc9240814d6a185#egg=django-multidb-router
+-e git://github.com/jbalogh/django-multidb-router.git@25ca0c68929144ed9020d89f2ea1e941c7f9aeca#egg=django-multidb-router
 -e git://github.com/jbalogh/django-cache-machine.git@bdee25ba4eeb20758da86f4013edbc48a77bcc6e#egg=django-cache-machine
 -e git://github.com/django-extensions/django-extensions.git#egg=django_extensions
 Jinja2==2.2.1

settings.py

@@ -33,7 +33,7 @@
     }
 }
 
-DATABASE_ROUTERS = ('multidb.MasterSlaveRouter',)
+DATABASE_ROUTERS = ('multidb.PinningMasterSlaveRouter',)
 
 # Put the aliases for your slave databases in this list
 SLAVE_DATABASES = []
@@ -122,6 +122,7 @@
 )
 
 MIDDLEWARE_CLASSES = (
+    'multidb.middleware.PinningRouterMiddleware',
     'sumo.middleware.LocaleURLMiddleware',
     'sumo.middleware.Forbidden403Middleware',
     'django.middleware.common.CommonMiddleware',