docker_container.rb in coursemology-evaluator-0.1.4

- old
+ new

@@ -13,14 +13,33 @@
       end
     end
 
     private
 
+    # Pulls the given image from Docker Hub.
+    #
+    # This caches images for 5 minutes, because the overhead for querying for images is quite high.
+    #
+    # @param [String] image The image to pull.
     def pull_image(image)
       ActiveSupport::Notifications.instrument('pull.docker.evaluator.coursemology',
-                                              image: image) do
-        Docker::Image.create('fromImage' => image)
+                                              image: image) do |payload|
+        cached([:image, image], expires_in: 5.minutes) do
+          Docker::Image.create('fromImage' => image)
+          payload[:cached] = false
+        end
       end
+    end
+
+    # Cache the result of the given block using the key given.
+    #
+    # @param [Array, String, Symbol] key The key to use. This will be expanded with
+    #   +ActiveSupport::Cache.expand_cache_key+.
+    # @param [Hash] options The options to use. These are the same as
+    #   +ActiveSupport::Cache::Store#fetch+.
+    def cached(key, options = {}, &proc)
+      key = ActiveSupport::Cache.expand_cache_key(key, name.underscore)
+      Coursemology::Evaluator.cache.fetch(key, options, &proc)
     end
   end
 
   # Waits for the container to exit the Running state.
   #