Add caching to the changes api since it is so expensive and can return large results.

endpoints/api.py

@@ -20,6 +20,7 @@ from auth.permissions import (ReadRepositoryPermission,
                               AdministerRepositoryPermission)
 from endpoints import registry
 from endpoints.web import common_login
+from util.cache import cache_control
 
 
 store = storage.load()
@@ -380,6 +381,7 @@ def get_image(namespace, repository, image_id):
 
 @app.route('/api/repository/<path:repository>/image/<image_id>/changes',
            methods=['GET'])
+@cache_control(max_age=60*60)  # Cache for one hour
 @parse_repository_name
 def get_image_changes(namespace, repository, image_id):
   permission = ReadRepositoryPermission(namespace, repository)

util/cache.py

@@ -0,0 +1,12 @@
+from functools import wraps
+
+
+def cache_control(max_age=55):
+  def wrap(f):
+    @wraps(f)
+    def add_max_age(*args, **kwargs):
+      response = f(*args, **kwargs)
+      response.headers['Cache-Control'] = 'max-age=%d' % max_age
+      return response
+    return add_max_age
+  return wrap