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)