'exclusive' class method

The 'exclusive' method can be used to mark certain instance methods as
always running exclusive. This has the side effect (which so happens to
be the main use case) of running code outside of a Ruby Fiber, allowing
that code to consumer more stack space than the 4kB stacks of YARV
fibers would otherwise allow.

CHANGES.md

@@ -1,3 +1,8 @@
+HEAD
+----
+* 'exclusive' class method marks methods as always exclusive and runs them
+  outside of a Fiber (useful if you need more stack than Fibers provide)
+
 0.11.0
 ------
 * Celluloid::Application constant permanently removed

lib/celluloid.rb

@@ -1,6 +1,7 @@
 require 'logger'
 require 'thread'
 require 'timeout'
+require 'set'
 
 module Celluloid
   SHUTDOWN_TIMEOUT = 120 # How long actors have to terminate
@@ -169,6 +170,13 @@ def use_mailbox(klass = nil, &block)
       end
     end
 
+    # Mark methods as running exclusively
+    def exclusive(*methods)
+      @exclusive_methods ||= Set.new
+      @exclusive_methods.merge methods.map(&:to_sym)
+    end
+    attr_reader :exclusive_methods
+
     # Create a mailbox for this actor
     def mailbox_factory
       if defined?(@mailbox_factory)
@@ -297,6 +305,11 @@ def exclusive(&block)
     Thread.current[:actor].exclusive(&block)
   end
 
+  # Are we currently exclusive
+  def exclusive?
+    Celluloid.exclusive?
+  end
+
   # Call a block after a given interval, returning a Celluloid::Timer object
   def after(interval, &block)
     Thread.current[:actor].after(interval, &block)

lib/celluloid/actor.rb

@@ -106,6 +106,7 @@ def initialize(subject)
       @subject      = subject
       @mailbox      = subject.class.mailbox_factory
       @exit_handler = subject.class.exit_handler
+      @exclusives   = subject.class.exclusive_methods
 
       @tasks     = Set.new
       @links     = Links.new
@@ -226,7 +227,11 @@ def sleep(interval)
     def handle_message(message)
       case message
       when Call
-        Task.new(:message_handler) { message.dispatch(@subject) }.resume
+        if @exclusives && @exclusives.include?(message.method)
+          exclusive { message.dispatch(@subject) }
+        else
+          Task.new(:message_handler) { message.dispatch(@subject) }.resume
+        end
       when Response
         message.call.task.resume message
       else

spec/support/actor_examples.rb

@@ -341,6 +341,22 @@ def signaled?; @signaled end
     end
   end
 
+  context :exclusive do
+    subject do
+      Class.new do
+        include included_module
+        def exclusive_example
+          exclusive?
+        end
+        exclusive :exclusive_example
+      end.new
+    end
+
+    it "supports exclusive methods" do
+      subject.exclusive_example.should be_true
+    end
+  end
+
   context :receiving do
     before do
       @receiver = Class.new do

spec/support/example_actor_class.rb

@@ -76,4 +76,4 @@ def delegates?(method_name)
       end
     end
   end
-end
+end