Merge 077c4a69ac into c2280e34ec

rest_framework/caches.py

@@ -0,0 +1,65 @@
+"""
+Provides a set of pluggable cache policies.
+"""
+from django.core.cache import cache
+from django.core.exceptions import ImproperlyConfigured
+from rest_framework.exceptions import PreconditionFailed
+
+
+class BaseCacheLookup(object):
+    def get_request_header(self):
+        raise ImproperlyConfigured('Subclass must implement `get_request_header`.')
+
+    def get_update_header(self):
+        raise ImproperlyConfigured('Subclass must implement `get_update_header`.')
+
+    def get_response_header(self, obj):
+        raise ImproperlyConfigured('Subclass must impelement `get_response_header`.')
+
+    def precondition_check(self, obj, request):
+        raise ImproperlyConfigured('Subclass must implement `precondition_check`.')
+
+    def resource_unchanged(self, request):
+        raise ImproperlyConfigured('Subclass must implement `resource_unchanged`.')
+
+
+class ETagCacheLookup(BaseCacheLookup):
+    """
+    """
+    etag_variable = 'etag'
+    request_header = 'HTTP_IF_NONE_MATCH'
+    update_header = 'HTTP_IF_MATCH'
+
+    @staticmethod
+    def get_cache_key(cls, pk):
+        try:
+            class_name = cls.__name__  # class
+        except AttributeError:
+            class_name = cls.__class__.__name__  # instance
+        return 'etag-{}-{}'.format(class_name, pk)
+
+    def get_etag(self, obj):
+        return getattr(obj, self.etag_variable)
+
+    def get_request_header(self):
+        return self.request_header
+
+    def get_update_header(self):
+        return self.update_header
+
+    def get_response_header(self, obj):
+        key = self.get_cache_key(obj, 'pk')
+        etag = self.get_etag(obj)
+        cache.set(key, etag)
+        return {'ETag': etag}
+
+    def precondition_check(self, obj, request):
+        if self.get_etag(obj) != request.META.get(self.get_update_header()):
+            raise PreconditionFailed
+
+    def resource_unchanged(self, request, key):
+        etag = cache.get(key)
+        header = request.META.get(self.get_request_header())
+        if etag is not None and etag == header:
+            return True
+        return False

rest_framework/exceptions.py

@@ -88,6 +88,14 @@ class Throttled(APIException):
             self.detail = detail or self.default_detail
 
 
+class PreconditionFailed(APIException):
+    status_code = status.HTTP_412_PRECONDITION_FAILED
+    default_detail = 'Object has been updated since you retrieved it.'
+
+    def __init__(self, detail=None):
+        self.detail = detail or self.default_detail
+
+
 class ConfigurationError(Exception):
     """
     Indicates an internal server error.

rest_framework/mixins.py

@@ -97,11 +97,18 @@ class RetrieveModelMixin(object):
     Should be mixed in with `SingleObjectAPIView`.
     """
     def retrieve(self, request, *args, **kwargs):
+        cached_object = self.check_preemptive_cache(request)
+        if cached_object:
+            return cached_object
+
         queryset = self.get_queryset()
         filtered_queryset = self.filter_queryset(queryset)
         self.object = self.get_object(filtered_queryset)
+
+        headers = self.get_cache_lookup_response_headers(self.object)
+
         serializer = self.get_serializer(self.object)
-        return Response(serializer.data)
+        return Response(serializer.data, headers=headers)
 
 
 class UpdateModelMixin(object):
@@ -122,6 +129,7 @@ class UpdateModelMixin(object):
             save_kwargs = {'force_insert': True}
             success_status_code = status.HTTP_201_CREATED
         else:
+            self.cache_precondition_check(self.object, request)
             created = False
             save_kwargs = {'force_update': True}
             success_status_code = status.HTTP_200_OK
@@ -166,5 +174,6 @@ class DestroyModelMixin(object):
     """
     def destroy(self, request, *args, **kwargs):
         obj = self.get_object()
+        self.cache_precondition_check(obj, request)
         obj.delete()
         return Response(status=status.HTTP_204_NO_CONTENT)

rest_framework/settings.py

@@ -47,6 +47,8 @@ DEFAULTS = {
     ),
     'DEFAULT_THROTTLE_CLASSES': (
     ),
+    'DEFAULT_CACHE_LOOKUP_CLASSES': (
+    ),
 
     'DEFAULT_CONTENT_NEGOTIATION_CLASS':
         'rest_framework.negotiation.DefaultContentNegotiation',

rest_framework/views.py

@@ -60,6 +60,7 @@ class APIView(View):
     throttle_classes = api_settings.DEFAULT_THROTTLE_CLASSES
     permission_classes = api_settings.DEFAULT_PERMISSION_CLASSES
     content_negotiation_class = api_settings.DEFAULT_CONTENT_NEGOTIATION_CLASS
+    cache_lookup_classes = api_settings.DEFAULT_CACHE_LOOKUP_CLASSES
 
     @classmethod
     def as_view(cls, **initkwargs):
@@ -241,6 +242,12 @@ class APIView(View):
             self._negotiator = self.content_negotiation_class()
         return self._negotiator
 
+    def get_cache_lookups(self):
+        """
+        Instantiates and returns the list of cache lookups that this view requires.
+        """
+        return [cache_lookup() for cache_lookup in self.cache_lookup_classes]
+
     # API policy implementation methods
 
     def perform_content_negotiation(self, request, force=False):
@@ -294,6 +301,22 @@ class APIView(View):
             if not throttle.allow_request(request, self):
                 self.throttled(request, throttle.wait())
 
+    def check_preemptive_cache(self, request):
+        for cache_lookup in self.get_cache_lookups():
+            cache_key = cache_lookup.get_cache_key(self.model, self.kwargs['pk'])
+            if cache_lookup.resource_unchanged(request, cache_key):
+                return Response(status=304)
+
+    def get_cache_lookup_response_headers(self, obj):
+        headers = {}
+        for cache_lookup in self.get_cache_lookups():
+            headers.update(cache_lookup.get_response_header(obj))
+        return headers
+
+    def cache_precondition_check(self, obj, request):
+        for cache_lookup in self.get_cache_lookups():
+            cache_lookup.precondition_check(obj, request)
+
     # Dispatch methods
 
     def initialize_request(self, request, *args, **kargs):