lib/finite_machine/observer.rb in finite_machine-0.14.0 vs lib/finite_machine/observer.rb in finite_machine-0.14.1

@@ -1,7 +1,9 @@
 # frozen_string_literal: true
 
+require "securerandom"
+
 require_relative "async_call"
 require_relative "callable"
 require_relative "hook_event"
 require_relative "hooks"
 require_relative "message_queue"
@@ -11,24 +13,10 @@
 module FiniteMachine
   # A class responsible for observing state changes
   class Observer < GenericDSL
     include Safety
 
-    # Clean up callback queue
-    #
-    # @api private
-    def self.cleanup_callback_queue
-      proc do
-        begin
-          if callback_queue.alive?
-            callback_queue.shutdown
-          end
-        rescue MessageQueueDeadError
-        end
-      end
-    end
-
     # The current state machine
     attr_reader :machine
 
     # The hooks to trigger around the transition lifecycle.
     attr_reader :hooks
@@ -42,17 +30,12 @@
     def initialize(machine)
       @machine = machine
       @hooks   = Hooks.new
 
       @machine.subscribe(self)
-      ObjectSpace.define_finalizer(self, self.class.cleanup_callback_queue)
     end
 
-    def callback_queue
-      @callback_queue ||= MessageQueue.new
-    end
-
     # Evaluate in current context
     #
     # @api private
     def call(&block)
       instance_eval(&block)
@@ -200,9 +183,38 @@
     # @api private
     def defer(callable, trans_event, *data)
       async_call = AsyncCall.new(machine, callable, trans_event, *data)
       callback_queue.start unless callback_queue.running?
       callback_queue << async_call
+    end
+
+    # Get an existing callback queue or create a new one
+    #
+    # @return [FiniteMachine::MessageQueue]
+    #
+    # @api private
+    def callback_queue
+      @callback_queue ||= MessageQueue.new.tap do
+        @queue_id = SecureRandom.uuid
+        ObjectSpace.define_finalizer(@queue_id, proc do
+          cleanup_callback_queue
+        end)
+      end
+    end
+
+    # Clean up the callback queue
+    #
+    # @return [Boolean, nil]
+    #
+    # @api private
+    def cleanup_callback_queue
+      ObjectSpace.undefine_finalizer(@queue_id) if @queue_id
+      return unless @callback_queue && callback_queue.alive?
+
+      begin
+        callback_queue.shutdown
+      rescue MessageQueueDeadError
+      end
     end
 
     # Create callable instance
     #
     # @api private