move Lock.token attribute into thread-local storage

redis/lock.py

@@ -1,3 +1,4 @@
+import threading
 import time as mod_time
 import uuid
 from redis.exceptions import LockError, WatchError
@@ -44,7 +45,8 @@ def __init__(self, redis, name, timeout=None, sleep=0.1,
         self.sleep = sleep
         self.blocking = blocking
         self.blocking_timeout = blocking_timeout
-        self.token = None
+        self.local = threading.local()
+        self.local.token = None
         if self.timeout and self.sleep > self.timeout:
             raise LockError("'sleep' must be less than 'timeout'")
 
@@ -79,7 +81,7 @@ def acquire(self, blocking=None, blocking_timeout=None):
             stop_trying_at = mod_time.time() + self.blocking_timeout
         while 1:
             if self.do_acquire(token):
-                self.token = token
+                self.local.token = token
                 return True
             if not blocking:
                 return False
@@ -98,10 +100,10 @@ def do_acquire(self, token):
 
     def release(self):
         "Releases the already acquired lock"
-        if self.token is None:
+        expected_token = self.local.token
+        if expected_token is None:
             raise LockError("Cannot release an unlocked lock")
-        expected_token = self.token
-        self.token = None
+        self.local.token = None
         self.do_release(expected_token)
 
     def do_release(self, expected_token):
@@ -122,7 +124,7 @@ def extend(self, additional_time):
         ``additional_time`` can be specified as an integer or a float, both
         representing the number of seconds to add.
         """
-        if self.token is None:
+        if self.local.token is None:
             raise LockError("Cannot extend an unlocked lock")
         if self.timeout is None:
             raise LockError("Cannot extend a lock with no timeout")
@@ -132,7 +134,7 @@ def do_extend(self, additional_time):
         pipe = self.redis.pipeline()
         pipe.watch(self.name)
         lock_value = pipe.get(self.name)
-        if lock_value != self.token:
+        if lock_value != self.local.token:
             raise LockError("Cannot extend a lock that's no longer owned")
         expiration = pipe.pttl(self.name)
         if expiration is None or expiration < 0:
@@ -236,7 +238,7 @@ def do_release(self, expected_token):
     def do_extend(self, additional_time):
         additional_time = int(additional_time * 1000)
         if not bool(self.lua_extend(keys=[self.name],
-                                    args=[self.token, additional_time],
+                                    args=[self.local.token, additional_time],
                                     client=self.redis)):
             raise LockError("Cannot extend a lock that's no longer owned")
         return True

tests/test_lock.py

@@ -16,7 +16,7 @@ def get_lock(self, redis, *args, **kwargs):
     def test_lock(self, sr):
         lock = self.get_lock(sr, 'foo')
         assert lock.acquire(blocking=False)
-        assert sr.get('foo') == lock.token
+        assert sr.get('foo') == lock.local.token
         assert sr.ttl('foo') == -1
         lock.release()
         assert sr.get('foo') is None
@@ -56,7 +56,7 @@ def test_context_manager(self, sr):
         # blocking_timeout prevents a deadlock if the lock can't be acquired
         # for some reason
         with self.get_lock(sr, 'foo', blocking_timeout=0.2) as lock:
-            assert sr.get('foo') == lock.token
+            assert sr.get('foo') == lock.local.token
         assert sr.get('foo') is None
 
     def test_high_sleep_raises_error(self, sr):
@@ -77,7 +77,7 @@ def test_releasing_lock_no_longer_owned_raises_error(self, sr):
         with pytest.raises(LockError):
             lock.release()
         # even though we errored, the token is still cleared
-        assert lock.token is None
+        assert lock.local.token is None
 
     def test_extend_lock(self, sr):
         lock = self.get_lock(sr, 'foo', timeout=10)