Merge pull request hovel#65 from hovel/tracker_mysql_fix

fixed issue with get_or_create method for topic/forum read tracker,

pybb/models.py

@@ -3,9 +3,10 @@
 import os.path
 import uuid
 
-from django.db import models
+from django.db import models, transaction
 from django.contrib.auth.models import User
 from django.core.urlresolvers import reverse
+from django.db.utils import IntegrityError
 from django.utils.html import strip_tags
 from django.utils.translation import ugettext_lazy as _
 from django.conf import settings
@@ -390,6 +391,26 @@ def size_display(self):
             return '%.2fMb' % (size / float(1024 * 1024))
 
 
+class TopicReadTrackerManager(models.Manager):
+    @transaction.commit_on_success
+    def get_or_create_tracker(self, user, topic):
+        """
+        Correctly create tracker in mysql db on default REPEATABLE READ transaction mode
+
+        It's known problem when standrard get_or_create method return can raise exception
+        with correct data in mysql database.
+        See http://stackoverflow.com/questions/2235318/how-do-i-deal-with-this-race-condition-in-django/2235624
+        """
+        is_new = True
+        try:
+            obj = TopicReadTracker.objects.create(user=user, topic=topic)
+        except IntegrityError:
+            transaction.commit()
+            obj = TopicReadTracker.objects.get(user=user, topic=topic)
+            is_new = False
+        return obj, is_new
+
+
 class TopicReadTracker(models.Model):
     """
     Save per user topic read tracking
@@ -398,12 +419,34 @@ class TopicReadTracker(models.Model):
     topic = models.ForeignKey(Topic, blank=True, null=True)
     time_stamp = models.DateTimeField(auto_now=True)
 
+    objects = TopicReadTrackerManager()
+
     class Meta(object):
         verbose_name = _('Topic read tracker')
         verbose_name_plural = _('Topic read trackers')
         unique_together = ('user', 'topic')
 
 
+class ForumReadTrackerManager(models.Manager):
+    @transaction.commit_on_success
+    def get_or_create_tracker(self, user, forum):
+        """
+        Correctly create tracker in mysql db on default REPEATABLE READ transaction mode
+
+        It's known problem when standrard get_or_create method return can raise exception
+        with correct data in mysql database.
+        See http://stackoverflow.com/questions/2235318/how-do-i-deal-with-this-race-condition-in-django/2235624
+        """
+        is_new = True
+        try:
+            obj = ForumReadTracker.objects.create(user=user, forum=forum)
+        except IntegrityError:
+            transaction.commit()
+            is_new = False
+            obj = ForumReadTracker.objects.get(user=user, forum=forum)
+        return obj, is_new
+
+
 class ForumReadTracker(models.Model):
     """
     Save per user forum read tracking
@@ -412,6 +455,8 @@ class ForumReadTracker(models.Model):
     forum = models.ForeignKey(Forum, blank=True, null=True)
     time_stamp = models.DateTimeField(auto_now=True)
 
+    objects = ForumReadTrackerManager()
+
     class Meta(object):
         verbose_name = _('Forum read tracker')
         verbose_name_plural = _('Forum read trackers')

pybb/views.py

@@ -7,7 +7,6 @@
 from django.core.exceptions import ObjectDoesNotExist, PermissionDenied
 from django.core.urlresolvers import reverse
 from django.contrib import messages
-from django.db import IntegrityError
 from django.db.models import F, Q
 from django.http import HttpResponseRedirect, HttpResponse, Http404, HttpResponseBadRequest,\
     HttpResponseForbidden
@@ -191,11 +190,7 @@ def mark_read(self, request, topic):
             forum_mark = None
         if (forum_mark is None) or (forum_mark.time_stamp < topic.updated):
             # Mark topic as readed
-            try:
-                topic_mark, new = TopicReadTracker.objects.get_or_create(topic=topic, user=request.user)
-            except IntegrityError: # duplicate mark
-                topic_mark = TopicReadTracker.objects.get(topic=topic, user=request.user)
-                new = False
+            topic_mark, new = TopicReadTracker.objects.get_or_create_tracker(topic=topic, user=request.user)
             if not new:
                 topic_mark.save()
 
@@ -209,10 +204,7 @@ def mark_read(self, request, topic):
                         user=request.user,
                         topic__forum=topic.forum
                         ).delete()
-                try:
-                    forum_mark, new = ForumReadTracker.objects.get_or_create(forum=topic.forum, user=request.user)
-                except IntegrityError: # duplicate mark
-                    forum_mark = ForumReadTracker.objects.get(forum=topic.forum, user=request.user)
+                forum_mark, new = ForumReadTracker.objects.get_or_create_tracker(forum=topic.forum, user=request.user)
                 forum_mark.save()
 
 
@@ -545,10 +537,7 @@ def post_ajax_preview(request):
 @login_required
 def mark_all_as_read(request):
     for forum in perms.filter_forums(request.user, Forum.objects.all()):
-        try:
-            forum_mark, new = ForumReadTracker.objects.get_or_create(forum=forum, user=request.user)
-        except IntegrityError: # duplicate mark
-            forum_mark = ForumReadTracker.objects.get(forum=forum, user=request.user)
+        forum_mark, new = ForumReadTracker.objects.get_or_create_tracker(forum=forum, user=request.user)
         forum_mark.save()
     TopicReadTracker.objects.filter(user=request.user).delete()
     msg = _('All forums marked as read')