Metastore TTL support

doc/configuration.markdown

@@ -124,4 +124,13 @@ which will act as the cache key generator:
 	end
 
 For more options see the [Rack::Request documentation](http://rack.rubyforge.org/doc/classes/Rack/Request.html)
-
+
+### `use_native_ttl`
+
+Passes on the expiration timestamp to the cache store. This may be necessary
+with some stores to keep them from filling up, e.g. if using a Redis backend and
+the `volatile-ttl` expiration policy.
+
+If using `memcached`, it will speed up misses slightly as the middleware won't
+need to fetch metadata and check timestamps.
+

lib/rack/cache/meta_store.rb

@@ -81,7 +81,11 @@ def store(request, response, entity_store)
       headers.delete 'Age'
 
       entries.unshift [stored_env, headers]
-      write key, entries
+      if request.env['rack-cache.use_native_ttl'] && response.fresh?
+        write key, entries, response.ttl
+      else
+        write key, entries
+      end
       key
     end
 
@@ -155,7 +159,7 @@ def read(key)
     # Store an Array of request/response pairs for the given key. Concrete
     # implementations should not attempt to filter or concatenate the
     # list in any way.
-    def write(key, negotiations)
+    def write(key, negotiations, ttl = nil)
       raise NotImplementedError
     end
 
@@ -188,7 +192,7 @@ def read(key)
         end
       end
 
-      def write(key, entries)
+      def write(key, entries, ttl = nil)
         @hash[key] = Marshal.dump(entries)
       end
 
@@ -226,7 +230,7 @@ def read(key)
         []
       end
 
-      def write(key, entries)
+      def write(key, entries, ttl = nil)
         tries = 0
         begin
           path = key_path(key)
@@ -325,9 +329,9 @@ def read(key)
         cache.get(key) || []
       end
 
-      def write(key, entries)
+      def write(key, entries, ttl = 0)
         key = hexdigest(key)
-        cache.set(key, entries)
+        cache.set(key, entries, ttl)
       end
 
       def purge(key)
@@ -359,9 +363,9 @@ def read(key)
         []
       end
 
-      def write(key, entries)
+      def write(key, entries, ttl = 0)
         key = hexdigest(key)
-        cache.set(key, entries)
+        cache.set(key, entries, ttl)
       end
 
       def purge(key)

test/meta_store_test.rb

@@ -253,6 +253,12 @@ def purge(*args); nil end
 
         @store.read(key).length.must_equal 2
       end
+
+      it 'takes a ttl parameter for #write' do
+        @store.write('/test', [[{},{}],[{},{}]], 0)
+        tuples = @store.read('/test')
+        tuples.must_equal [ [{},{}], [{},{}] ]
+      end
     end
   end
 end