potential fix for #2192

app/controllers/forum_topics_controller.rb

@@ -17,7 +17,6 @@ class ForumTopicsController < ApplicationController
   end
 
   def index
-    # session[:read_forum_topics] = ""
     @query = ForumTopic.active.search(params[:search])
     @forum_topics = @query.order("is_sticky DESC, updated_at DESC").paginate(params[:page], :limit => params[:limit], :search_count => params[:search])
     @read_forum_topic_ids = read_forum_topic_ids

app/models/forum_topic.rb

@@ -124,9 +124,11 @@ class ForumTopic < ActiveRecord::Base
     end
     hash[id.to_s] = updated_at.to_i.to_s
     result = hash.to_a.flatten.join(" ")
-    if result.size > 3000
+    while result.size > 3000
       ids = result.scan(/\S+/)
+      print "slicing from #{result.size} to "
       result = ids[(ids.size / 2)..-1].join(" ")
+      puts result.size
     end
     update_last_forum_read_at(hash.keys)
     result

test/functional/forum_topics_controller_test.rb

@@ -16,6 +16,25 @@ class ForumTopicsControllerTest < ActionController::TestCase
       CurrentUser.ip_addr = nil
     end
 
+    context "show action" do
+      should "render" do
+        get :show, {:id => @forum_topic.id}
+        assert_response :success
+      end
+
+      context "when the read_forum_topics session exceeds the maximum cookie size" do
+        setup do
+          @cookie_data = 1.upto(10_000).to_a.join(" ")
+        end
+
+        should "truncate" do
+          get :show, {:id => @forum_topic.id}, {:user_id => @user.id, :read_forum_topics => @cookie_data}
+          assert_response :success
+          assert_equal(1570, session[:read_forum_topics].size)
+        end
+      end
+    end
+
     context "index action" do
       should "list all forum topics" do
         get :index