Added enhancements to Worker.

* They are now aware of shutdowns that occur, and will terminate
  themselves.
* They keep track of messages_processed after every run_loop().
* They pass message IDs to the WorkerError class.

lib/queue_stick/worker.rb

@@ -21,13 +21,17 @@ def delete_message_from_queue(message)
     end
 
     def run_loop
+      # Exit the run loop if we get a shutdown request.
+      Thread.current.exit if Thread.current[:shutdown]
+
       message = get_message_from_queue
 
       begin
         process(message.body)
         delete_message_from_queue(message)
+        counter(:messages_processed).increment!
       rescue Exception => process_error
-        error = WorkerError.new(:dummy_id) # TODO(dbalatero): message_id?!
+        error = WorkerError.new(message.id)
         error.exceptions << process_error
         begin
           recover

spec/queue_stick/worker_spec.rb

@@ -40,6 +40,14 @@ class RunLoopTestWorker < QueueStick::Worker
       }.should_not raise_error
     end
 
+    it "should automatically increment messages_processed on each loop" do
+      worker = QueueStick::MockWorker.new
+      worker.run_loop
+      worker.counter(:messages_processed).counts[0].should == 1
+      worker.run_loop
+      worker.counter(:messages_processed).counts[0].should == 2
+    end
+
     it "should call delete_message_from_queue if process succeeds" do
       @worker.should_receive(:process).and_return(true)
       @worker.should_receive(:delete_message_from_queue).and_return(true)
@@ -53,6 +61,17 @@ class RunLoopTestWorker < QueueStick::Worker
       @worker.run_loop
     end
 
+    it "should terminate after a run if the current thread's :shutdown variable is set" do
+      worker = QueueStick::MockWorker.new
+      thread = Thread.new do
+        worker.run_loop while true
+      end
+      thread[:shutdown] = true
+
+      thread.join
+      thread.should_not be_alive
+    end
+
     it "should log errors when process fails" do
       @worker.should_receive(:process).and_raise(Exception)
       @worker.should_receive(:recover).and_return(true)