Support idle_timeout in global compiler (#175)

lib/sass/compiler.rb

@@ -26,7 +26,7 @@ module Sass
   #   sass.close
   class Compiler
     def initialize
-      @dispatcher = ResilientDispatcher.new
+      @dispatcher = ResilientDispatcher.new(Dispatcher)
     end
 
     # Compiles the Sass file at +path+ to CSS.

lib/sass/compiler/dispatcher.rb

@@ -35,7 +35,7 @@ def unsubscribe(id)
               close
             end
           else
-            @id = 1
+            idle
           end
         end
       end
@@ -90,6 +90,12 @@ def send_proto(...)
         @connection.write(...)
       end
 
+      private
+
+      def idle
+        @id = 1
+      end
+
       # The {Channel} between {Dispatcher} and {Host}.
       class Channel
         attr_reader :id

lib/sass/compiler/resilient_dispatcher.rb

@@ -6,8 +6,9 @@ class Compiler
     #
     # It recovers from failures and continues to function.
     class ResilientDispatcher
-      def initialize
-        @dispatcher = Dispatcher.new
+      def initialize(dispatcher_class)
+        @dispatcher_class = dispatcher_class
+        @dispatcher = @dispatcher_class.new
         @mutex = Mutex.new
       end
 
@@ -29,7 +30,7 @@ def connect(...)
         @mutex.synchronize do
           @dispatcher.connect(...)
         rescue Errno::EBUSY
-          @dispatcher = Dispatcher.new
+          @dispatcher = @dispatcher_class.new
           @dispatcher.connect(...)
         end
       end

lib/sass/embedded.rb

@@ -54,7 +54,43 @@ def compiler
       @mutex.synchronize do
         return @compiler if @compiler
 
-        compiler = Compiler.new
+        compiler = Class.new(Compiler) do
+          def initialize
+            @dispatcher = self.class.const_get(:ResilientDispatcher).new(Class.new(self.class.const_get(:Dispatcher)) do
+              def initialize
+                super
+
+                idle_timeout = 10
+                @last_accessed_time = current_time
+
+                Thread.new do
+                  duration = idle_timeout
+                  loop do
+                    sleep(duration.negative? ? idle_timeout : duration)
+                    evicted = @mutex.synchronize do
+                      duration = idle_timeout - (current_time - @last_accessed_time)
+                      @id = 0xffffffff if @observers.empty? && duration.negative?
+                    end
+                    break if evicted
+                  end
+                  close
+                end
+              end
+
+              private
+
+              def idle
+                super
+
+                @last_accessed_time = current_time
+              end
+
+              def current_time
+                Process.clock_gettime(Process::CLOCK_MONOTONIC)
+              end
+            end)
+          end
+        end.new
 
         Process.singleton_class.prepend(Module.new do
           define_method :_fork do