1 files changed, 104 insertions, 0 deletions
diff --git a/activesupport/lib/active_support/cache/strategy/local_cache.rb b/activesupport/lib/active_support/cache/strategy/local_cache.rb
new file mode 100644
index 0000000000..621358d701
--- /dev/null
+++ b/activesupport/lib/active_support/cache/strategy/local_cache.rb
@@ -0,0 +1,104 @@
+module ActiveSupport
+  module Cache
+    module Strategy
+      module LocalCache
+        # this allows caching of the fact that there is nothing in the remote cache
+        NULL = 'remote_cache_store:null'
+
+        def with_local_cache
+          Thread.current[thread_local_key] = MemoryStore.new
+          yield
+        ensure
+          Thread.current[thread_local_key] = nil
+        end
+
+        def middleware
+          @middleware ||= begin
+            klass = Class.new
+            klass.class_eval(<<-EOS, __FILE__, __LINE__)
+              def initialize(app)
+                @app = app
+              end
+
+              def call(env)
+                Thread.current[:#{thread_local_key}] = MemoryStore.new
+                @app.call(env)
+              ensure
+                Thread.current[:#{thread_local_key}] = nil
+              end
+            EOS
+            klass
+          end
+        end
+
+        def read(key, options = nil)
+          value = local_cache && local_cache.read(key)
+          if value == NULL
+            nil
+          elsif value.nil?
+            value = super
+            local_cache.write(key, value || NULL) if local_cache
+            value
+          else
+            # forcing the value to be immutable
+            value.dup
+          end
+        end
+
+        def write(key, value, options = nil)
+          value = value.to_s if respond_to?(:raw?) && raw?(options)
+          local_cache.write(key, value || NULL) if local_cache
+          super
+        end
+
+        def delete(key, options = nil)
+          local_cache.write(key, NULL) if local_cache
+          super
+        end
+
+        def exist(key, options = nil)
+          value = local_cache.read(key) if local_cache
+          if value == NULL
+            false
+          elsif value
+            true
+          else
+            super
+          end
+        end
+
+        def increment(key, amount = 1)
+          if value = super
+            local_cache.write(key, value.to_s) if local_cache
+            value
+          else
+            nil
+          end
+        end
+
+        def decrement(key, amount = 1)
+          if value = super
+            local_cache.write(key, value.to_s) if local_cache
+            value
+          else
+            nil
+          end
+        end
+
+        def clear
+          local_cache.clear if local_cache
+          super
+        end
+
+        private
+          def thread_local_key
+            @thread_local_key ||= "#{self.class.name.underscore}_local_cache".gsub("/", "_").to_sym
+          end
+
+          def local_cache
+            Thread.current[thread_local_key]
+          end
+      end
+    end
+  end
+end