Added #on_error callback to ActorContext.

Author: jdantonio

lib/concurrent/actor_context.rb

@@ -13,6 +13,9 @@ def on_reset
     def on_shutdown
     end
 
+    def on_error(time, message, exception)
+    end
+
     def self.included(base)
 
       class << base

lib/concurrent/simple_actor_ref.rb

@@ -95,6 +95,7 @@ def run_message_loop
         begin
           result = @actor.receive(*message.payload)
         rescue @exception_class => ex
+          @actor.on_error(Time.now, message.payload, ex)
           @actor.on_reset if @reset_on_error
         ensure
           now = Time.now

spec/concurrent/actor_ref_shared.rb

@@ -231,6 +231,24 @@ def receive(*msg)
     end
   end
 
+  context '#on_error' do
+
+    specify 'is not called on success' do
+      actor = subject.instance_variable_get(:@actor)
+      actor.should_not_receive(:on_error).with(any_args)
+      subject.post(:foo)
+      sleep(0.1)
+    end
+
+    specify 'is called when a message raises an exception' do
+      actor = subject.instance_variable_get(:@actor)
+      actor.should_receive(:on_error).
+        with(anything, [:poison], an_instance_of(StandardError))
+      subject.post(:poison)
+      sleep(0.1)
+    end
+  end
+
   context 'observation' do
 
     let(:observer_class) do