adding back in the decr

swift/common/memcached.py

@@ -209,6 +209,19 @@ class MemcacheRing(object):
             except Exception, e:
                 self._exception_occurred(server, e)
 
+    def decr(self, key, delta=1, timeout=0):
+        """
+        Decrements a key which has a numeric value by delta. Calls incr with
+        -delta.
+
+        :param key: key
+        :param delta: amount to subtract to the value of key (or set the
+                      value to 0 if the key is not found) will be cast to
+                      an int
+        :param timeout: ttl in memcache
+        """
+        self.incr(key, delta=-delta, timeout=timeout)
+
     def delete(self, key):
         """
         Deletes a key/value pair from memcache.

swift/common/middleware/ratelimit.py

@@ -148,7 +148,7 @@ class RateLimitMiddleware(object):
         max_sleep_m = self.max_sleep_time_seconds * self.clock_accuracy
         if max_sleep_m - need_to_sleep_m <= self.clock_accuracy * 0.01:
             # treat as no-op decrement time
-            self.memcache_client.incr(key, delta=-time_per_request_m)
+            self.memcache_client.decr(key, delta=time_per_request_m)
             raise MaxSleepTimeHit("Max Sleep Time Exceeded: %s" %
                                   need_to_sleep_m)
 

test/unit/common/middleware/test_ratelimit.py

@@ -41,6 +41,9 @@ class FakeMemcache(object):
             self.store[key] = 0
         return int(self.store[key])
 
+    def decr(self, key, delta=1, timeout=0):
+        return self.incr(key, delta=-delta, timeout=timeout)
+
     @contextmanager
     def soft_lock(self, key, timeout=0, retries=5):
         yield True

test/unit/common/test_memcached.py

@@ -167,6 +167,19 @@ class TestMemcached(unittest.TestCase):
         memcache_client.incr('some_key', delta=-15)
         self.assertEquals(memcache_client.get('some_key'), '0')
 
+    def test_decr(self):
+        memcache_client = memcached.MemcacheRing(['1.2.3.4:11211'])
+        mock = MockMemcached()
+        memcache_client._client_cache['1.2.3.4:11211'] = [(mock, mock)] * 2
+        memcache_client.decr('some_key', delta=5)
+        self.assertEquals(memcache_client.get('some_key'), '0')
+        memcache_client.incr('some_key', delta=15)
+        self.assertEquals(memcache_client.get('some_key'), '15')
+        memcache_client.decr('some_key', delta=4)
+        self.assertEquals(memcache_client.get('some_key'), '11')
+        memcache_client.decr('some_key', delta=15)
+        self.assertEquals(memcache_client.get('some_key'), '0')
+
     def test_retry(self):
         logging.getLogger().addHandler(NullLoggingHandler())
         memcache_client = memcached.MemcacheRing(['1.2.3.4:11211', '1.2.3.5:11211'])