Merge pull request #13673 from edx/common_cleanup/cache_toolbox

Move cache_toolbox from common to openedx/core

cms/envs/common.py

@@ -348,7 +348,7 @@ MIDDLEWARE_CLASSES = (
     'method_override.middleware.MethodOverrideMiddleware',
 
     # Instead of AuthenticationMiddleware, we use a cache-backed version
-    'cache_toolbox.middleware.CacheBackedAuthenticationMiddleware',
+    'openedx.core.djangoapps.cache_toolbox.middleware.CacheBackedAuthenticationMiddleware',
     # Enable SessionAuthenticationMiddleware in order to invalidate
     # user sessions after a password change.
     'django.contrib.auth.middleware.SessionAuthenticationMiddleware',

lms/envs/common.py

@@ -1098,7 +1098,7 @@ MIDDLEWARE_CLASSES = (
 
     # Instead of AuthenticationMiddleware, we use a cached backed version
     #'django.contrib.auth.middleware.AuthenticationMiddleware',
-    'cache_toolbox.middleware.CacheBackedAuthenticationMiddleware',
+    'openedx.core.djangoapps.cache_toolbox.middleware.CacheBackedAuthenticationMiddleware',
     # Enable SessionAuthenticationMiddleware in order to invalidate
     # user sessions after a password change.
     'django.contrib.auth.middleware.SessionAuthenticationMiddleware',

openedx/core/djangoapps/cache_toolbox/app_settings.py

@@ -1,3 +1,7 @@
+"""
+Settings for cache_toolbox.
+"""
+
 from django.conf import settings
 
 # Default cache timeout

openedx/core/djangoapps/cache_toolbox/core.py

@@ -34,40 +34,36 @@ def get_instance(model, instance_or_pk, timeout=None, using=None):
         True
 
     """
-    pk = getattr(instance_or_pk, 'pk', instance_or_pk)
+    primary_key = getattr(instance_or_pk, 'pk', instance_or_pk)
     key = instance_key(model, instance_or_pk)
     data = cache.get(key)
 
     if data is not None:
         try:
             # Try and construct instance from dictionary
-            instance = model(pk=pk, **data)
+            instance = model(pk=primary_key, **data)
 
             # Ensure instance knows that it already exists in the database,
             # otherwise we will fail any uniqueness checks when saving the
             # instance.
-            instance._state.adding = False
+            instance._state.adding = False  # pylint: disable=protected-access
 
             # Specify database so that instance is setup correctly. We don't
             # namespace cached objects by their origin database, however.
-            instance._state.db = using or DEFAULT_DB_ALIAS
+            instance._state.db = using or DEFAULT_DB_ALIAS  # pylint: disable=protected-access
 
             return instance
-        except:
+        except:  # pylint: disable=bare-except
             # Error when deserialising - remove from the cache; we will
             # fallback and return the underlying instance
             cache.delete(key)
 
     # Use the default manager so we are never filtered by a .get_queryset()
 
-#    import logging
-#    log = logging.getLogger("tracking")
-#    log.info( str(pk) )
-
-    instance = model._default_manager.using(using).get(pk=pk)
+    instance = model._default_manager.using(using).get(pk=primary_key)  # pylint: disable=protected-access
 
     data = {}
-    for field in instance._meta.fields:
+    for field in instance._meta.fields:  # pylint: disable=protected-access
         # Harmless to save, but saves space in the dictionary - we already know
         # the primary key when we lookup
         if field.primary_key:
@@ -76,8 +72,8 @@ def get_instance(model, instance_or_pk, timeout=None, using=None):
         if field.get_internal_type() == 'FileField':
             # Avoid problems with serializing FileFields
             # by only serializing the file name
-            file = getattr(instance, field.attname)
-            data[field.attname] = file.name
+            file_value = getattr(instance, field.attname)
+            data[field.attname] = file_value.name
         else:
             data[field.attname] = getattr(instance, field.attname)
 

openedx/core/djangoapps/cache_toolbox/middleware.py

@@ -67,7 +67,7 @@ with::
 
     MIDDLEWARE_CLASSES = [
         ...
-        'cache_toolbox.middleware.CacheBackedAuthenticationMiddleware',
+        'openedx.core.djangoapps.cache_toolbox.middleware.CacheBackedAuthenticationMiddleware',
         ...
     ]
 
@@ -93,6 +93,9 @@ log = getLogger(__name__)
 
 
 class CacheBackedAuthenticationMiddleware(AuthenticationMiddleware):
+    """
+    See documentation above.
+    """
     def __init__(self):
         cache_model(User)
 
@@ -110,7 +113,7 @@ class CacheBackedAuthenticationMiddleware(AuthenticationMiddleware):
                 # Raise an exception to fall through to the except clause below.
                 raise Exception
             self._verify_session_auth(request)
-        except:
+        except:  # pylint: disable=bare-except
             # Fallback to constructing the User from the database.
             super(CacheBackedAuthenticationMiddleware, self).process_request(request)
 

openedx/core/djangoapps/cache_toolbox/model.py

@@ -60,18 +60,28 @@ from .core import get_instance, delete_instance
 
 
 def cache_model(model, timeout=None):
+    """
+    Adds utility methods to the given model to obtain
+    ``ForeignKey`` instances via the cache.
+    """
     if hasattr(model, 'get_cached'):
         # Already patched
         return
 
-    def clear_cache(sender, instance, *args, **kwargs):
+    def clear_cache(sender, instance, *args, **kwargs):  # pylint: disable=unused-argument
+        """
+        Clears the cache for the given instance.
+        """
         delete_instance(sender, instance)
 
     post_save.connect(clear_cache, sender=model, weak=False)
     post_delete.connect(clear_cache, sender=model, weak=False)
 
     @classmethod
-    def get(cls, pk, using=None):
+    def get(cls, pk, using=None):  # pylint: disable=invalid-name
+        """
+        Returns the model for the given primary key (pk).
+        """
         if pk is None:
             return None
         return get_instance(cls, pk, timeout, using)

openedx/core/djangoapps/cache_toolbox/relation.py

@@ -69,18 +69,25 @@ Support
 ``cache_relation`` currently only works with ``OneToOneField`` fields. Support
 for regular ``ForeignKey`` fields is planned.
 """
-
 from django.db.models.signals import post_save, post_delete
 
 from .core import get_instance, delete_instance
 
 
 def cache_relation(descriptor, timeout=None):
+    """
+    Adds utility methods to a model to obtain related
+    model instances via a cache.
+    """
     rel = descriptor.related
     related_name = '%s_cache' % rel.field.related_query_name()
 
     @property
     def get(self):
+        """
+        Returns the cached value of the related model if found
+        in the cache. Otherwise gets and caches the related model.
+        """
         # Always use the cached "real" instance if available
         try:
             return getattr(self, descriptor.cache_name)
@@ -93,10 +100,6 @@ def cache_relation(descriptor, timeout=None):
         except AttributeError:
             pass
 
-#        import logging
-#        log = logging.getLogger("tracking")
-#        log.info( "DEBUG: "+str(str(rel.model)+"/"+str(self.pk) ))
-
         instance = get_instance(rel.model, self.pk, timeout)
 
         setattr(self, '_%s_cache' % related_name, instance)
@@ -107,13 +110,24 @@ def cache_relation(descriptor, timeout=None):
     # Clearing cache
 
     def clear(self):
+        """
+        Clears the cache of all related models of self.
+        """
         delete_instance(rel.model, self)
 
     @classmethod
-    def clear_pk(cls, *instances_or_pk):
+    def clear_pk(cls, *instances_or_pk):  # pylint: disable=unused-argument
+        """
+        Clears the cache of all related models of
+        the provided instances_or_pk.
+        """
         delete_instance(rel.model, *instances_or_pk)
 
-    def clear_cache(sender, instance, *args, **kwargs):
+    def clear_cache(sender, instance, *args, **kwargs):  # pylint: disable=unused-argument
+        """
+        Clears the cache of all related models of the
+        given instance.
+        """
         delete_instance(rel.model, instance)
 
     setattr(rel.parent_model, '%s_clear' % related_name, clear)

openedx/core/djangoapps/cache_toolbox/templatetags/cache_toolbox.py

@@ -1,12 +1,21 @@
+"""
+Implementation of custom django template tags for
+automatically caching template fragments.
+"""
 from django import template
 from django.core.cache import cache
 from django.template import Node, TemplateSyntaxError, Variable
 from django.template import resolve_variable
 
-register = template.Library()
+register = template.Library()  # pylint: disable=invalid-name
 
 
 class CacheNode(Node):
+    """
+    Subclass of django's template Node class that
+    caches the rendered value of a template fragment. This is a
+    simpler implementation of django.templatetags.cache.CacheNode.
+    """
     def __init__(self, nodelist, expire_time, key):
         self.nodelist = nodelist
         self.expire_time = Variable(expire_time)
@@ -46,6 +55,11 @@ def cachedeterministic(parser, token):
 
 
 class ShowIfCachedNode(Node):
+    """
+    Subclass of django's template Node class that
+    renders the cached value for the given key, only
+    if already cached.
+    """
     def __init__(self, key):
         self.key = key
 
@@ -55,7 +69,7 @@ class ShowIfCachedNode(Node):
 
 
 @register.tag
-def showifcached(parser, token):
+def showifcached(parser, token):  # pylint: disable=unused-argument
     """
     Show content if it exists in the cache, otherwise display nothing.