diff --git a/app/models/task.rb b/app/models/task.rb
--- a/app/models/task.rb
+++ b/app/models/task.rb
@@ -1,2 +1,40 @@
 class Task < ActiveRecord::Base
+
+  STATUS_GRADING = 0
+  STATUS_INQUEUE = 1
+  STATUS_COMPLETE = 2
+
+  def status_inqueue
+    self.status = Task::STATUS_INQUEUE
+  end
+
+  def status_grading
+    self.status = Task::STATUS_GRADING
+  end
+
+  def status_complete
+    self.status = Task::STATUS_COMPLETE
+  end
+
+  def self.get_inqueue_and_change_status(status)
+    task = nil
+    begin
+      Task.transaction do
+        task = Task.find(:first, 
+                         :order => "created_at", 
+                         :conditions => {:status=> Task::STATUS_INQUEUE}, 
+                         :lock => true)
+        if task!=nil
+          task.status = status
+          task.save!
+        end
+      end
+      
+    rescue
+      task = nil
+      
+    end
+    task
+  end
+
 end