Adds Module#synchronize for easier method-level synchronization.

2 files changed, 36 insertions, 0 deletions

diff --git a/activesupport/lib/active_support/core_ext/module.rb b/activesupport/lib/active_support/core_ext/module.rb
index 34fcbd124b..392ba99f4e 100644
--- a/activesupport/lib/active_support/core_ext/module.rb
+++ b/activesupport/lib/active_support/core_ext/module.rb
@@ -7,6 +7,7 @@ require 'active_support/core_ext/module/introspection'
 require 'active_support/core_ext/module/loading'
 require 'active_support/core_ext/module/aliasing'
 require 'active_support/core_ext/module/model_naming'
+require 'active_support/core_ext/module/synchronization'
 
 class Module
   include ActiveSupport::CoreExt::Module::ModelNaming
diff --git a/activesupport/lib/active_support/core_ext/module/synchronization.rb b/activesupport/lib/active_support/core_ext/module/synchronization.rb
new file mode 100644
index 0000000000..bf7740f851
--- /dev/null
+++ b/activesupport/lib/active_support/core_ext/module/synchronization.rb
@@ -0,0 +1,35 @@
+class Module
+  # Synchronize access around a method, delegating synchronization to a
+  # particular mutex. A mutex (either a Mutex, or any object that responds to 
+  # #synchronize and yields to a block) must be provided as a final :with option.
+  # The :with option should be a symbol or string, and can represent a method, 
+  # constant, or instance or class variable.
+  # Example:
+  #   class SharedCache
+  #     @@lock = Mutex.new
+  #     def expire
+  #       ...
+  #     end
+  #     synchronize :expire, :with => :@@lock
+  #   end
+  def synchronize(*methods)
+    options = methods.extract_options!
+    unless options.is_a?(Hash) && with = options[:with]
+      raise ArgumentError, "Synchronization needs a mutex. Supply an options hash with a :with key as the last argument (e.g. synchronize :hello, :with => :@mutex)."
+    end
+
+    methods.each do |method|
+      if instance_methods.include?("#{method}_without_synchronization")
+        raise ArgumentError, "#{method} is already synchronized. Double synchronization is not currently supported."
+      end
+      module_eval(<<-EOS, __FILE__, __LINE__)
+        def #{method}_with_synchronization(*args, &block)
+          #{with}.synchronize do
+            #{method}_without_synchronization(*args,&block)
+          end
+        end
+      EOS
+      alias_method_chain method, :synchronization
+    end
+  end
+end
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