CELERY_MAX_CACHED_RESULTS=-1 will now disable the result cache

celery/backends/base.py

@@ -52,6 +52,12 @@ def unpickle_backend(cls, args, kwargs):
     return cls(*args, app=current_app._get_current_object(), **kwargs)
 
 
+class _nulldict(dict):
+
+    def __setitem__(self, k, v):
+        pass
+
+
 class BaseBackend(object):
     READY_STATES = states.READY_STATES
     UNREADY_STATES = states.UNREADY_STATES
@@ -90,9 +96,8 @@ class BaseBackend(object):
         (self.content_type,
          self.content_encoding,
          self.encoder) = serializer_registry._encoders[self.serializer]
-        self._cache = LRUCache(
-            limit=max_cached_results or conf.CELERY_MAX_CACHED_RESULTS,
-        )
+        cmax = max_cached_results or conf.CELERY_MAX_CACHED_RESULTS
+        self._cache = _nulldict() if cmax == -1 else LRUCache(limit=cmax)
         self.accept = prepare_accept_content(
             conf.CELERY_ACCEPT_CONTENT if accept is None else accept,
         )

celery/tests/backends/test_amqp.py

@@ -33,8 +33,8 @@ class test_AMQPBackend(AppCase):
         return AMQPBackend(self.app, **opts)
 
     def test_mark_as_done(self):
-        tb1 = self.create_backend()
-        tb2 = self.create_backend()
+        tb1 = self.create_backend(max_cached_results=1)
+        tb2 = self.create_backend(max_cached_results=1)
 
         tid = uuid()
 
@@ -175,7 +175,7 @@ class test_AMQPBackend(AppCase):
         class MockBackend(AMQPBackend):
             Queue = MockBinding
 
-        backend = MockBackend(self.app)
+        backend = MockBackend(self.app, max_cached_results=100)
         backend._republish = Mock()
 
         yield results, backend, Message
@@ -262,7 +262,7 @@ class test_AMQPBackend(AppCase):
                 b.drain_events(Connection(), consumer, timeout=0.1)
 
     def test_get_many(self):
-        b = self.create_backend()
+        b = self.create_backend(max_cached_results=10)
 
         tids = []
         for i in range(10):

celery/tests/backends/test_base.py

@@ -234,9 +234,10 @@ class test_BaseBackend_dict(AppCase):
         self.assertIsInstance(self.b.prepare_value(g), self.app.GroupResult)
 
     def test_is_cached(self):
-        self.b._cache['foo'] = 1
-        self.assertTrue(self.b.is_cached('foo'))
-        self.assertFalse(self.b.is_cached('false'))
+        b = BaseBackend(app=self.app, max_cached_results=1)
+        b._cache['foo'] = 1
+        self.assertTrue(b.is_cached('foo'))
+        self.assertFalse(b.is_cached('false'))
 
 
 class test_KeyValueStoreBackend(AppCase):

docs/configuration.rst

@@ -1142,12 +1142,8 @@ CELERY_MAX_CACHED_RESULTS
 Result backends caches ready results used by the client.
 
 This is the total number of results to cache before older results are evicted.
-The default is 5000.  0 or None means no limit.
-
-.. note::
-    
-    These results are kept in memory.  Reduce this setting if your Celery is utilizing
-    a large amount of memory.
+The default is 5000.  0 or None means no limit, and a value of :const:`-1`
+will disable the cache.
 
 .. setting:: CELERY_CHORD_PROPAGATES