Speed up memcache lock

Simplify sleep timeouts calculation removing progressive scale.

Closes-bug: #1395688
Change-Id: I0f1b620df9631a4b081e8c0be93d8a9b2d60e105
(cherry picked from commit ee93b64af4f64e8e7b903e70d44eb021ab97c9ef)

1 files changed, 4 insertions, 8 deletions

diff --git a/keystone/common/kvs/backends/memcached.py b/keystone/common/kvs/backends/memcached.py
index 0d8eeb8b5..463243db8 100644
--- a/keystone/common/kvs/backends/memcached.py
+++ b/keystone/common/kvs/backends/memcached.py
@@ -57,20 +57,16 @@ class MemcachedLock(object):
 
     def acquire(self, wait=True):
         client = self.client_fn()
-        i = 0
-        while True:
+        for i in range(self.max_lock_attempts):
             if client.add(self.key, 1, self.lock_timeout):
                 return True
             elif not wait:
                 return False
             else:
-                sleep_time = (((i + 1) * random.random()) + 2 ** i) / 2.5
+                sleep_time = random.random()
                 time.sleep(sleep_time)
-            if i <= self.max_lock_attempts:
-                i += 1
-            else:
-                raise exception.UnexpectedError(
-                    _('Maximum lock attempts on %s occurred.') % self.key)
+        raise exception.UnexpectedError(
+            _('Maximum lock attempts on %s occurred.') % self.key)
 
     def release(self):
         client = self.client_fn()