diff --git a/app/models/grader_process.rb b/app/models/grader_process.rb
--- a/app/models/grader_process.rb
+++ b/app/models/grader_process.rb
@@ -1,5 +1,7 @@
 class GraderProcess < ActiveRecord::Base
   
+  belongs_to :task
+
   def self.find_by_ip_and_pid(ip,pid)
     return GraderProcess.find(:first, 
                               :conditions => { 
@@ -8,10 +10,43 @@
                               })
   end
 
-  def self.report_active(ip,pid,mode)
+  def self.register(ip,pid,mode)
+    grader = GraderProcess.find_by_ip_and_pid(ip,pid)
+    if grader
+      grader.mode = mode
+      grader.active = nil
+      grader.task_id = nil
+      grader.save
+    else
+      grader = GraderProcess.create(:ip => ip, 
+                                    :pid => pid, 
+                                    :mode => mode)
+    end
+    grader
+  end
+
+  def self.find_stalled_process()
+    GraderProcess.find(:all,
+                       :conditions => ["active AND updated_at < ?",
+                                       Time.now.gmtime - GraderProcess.stalled_time])
+  end
+  
+  def report_active(task=nil)
+    self.active = true
+    self.task = task
+    self.save
   end                
 
-  def self.report_inactive(ip,pid,mode)
+  def report_inactive()
+    self.active = false
+    self.task = nil
+    self.save
   end                
 
+  protected
+
+  def self.stalled_time()
+    return 1.minute
+  end
+
 end