repair backwards incompat redis lock changes

Fixed regression caused by backwards-incompatible API changes in Redis that
caused the "distributed lock" feature to not function.

This commit also updates black which was not passing
due to the older version having dependency issues

Fixes: #220
Change-Id: Ibba3307dbfd9dfeacc08af79800b681ce160dea9

Author: zzzeek

.pre-commit-config.yaml

@@ -2,25 +2,25 @@
 # See https://pre-commit.com/hooks.html for more hooks
 repos:
 -   repo: https://github.com/python/black
-    rev: 21.5b1
+    rev: 22.3.0
     hooks:
     -   id: black
 
 -   repo: https://github.com/sqlalchemyorg/zimports
-    rev: v0.4.1
+    rev: v0.6.0
     hooks:
     -   id: zimports
         args:
             - --keep-unused-type-checking
 
 -   repo: https://github.com/pycqa/flake8
-    rev: 3.9.2
+    rev: 4.0.1
     hooks:
     -   id: flake8
         additional_dependencies:
           - flake8-import-order
           - flake8-builtins
-          - flake8-docstrings>=1.3.1
+          - flake8-docstrings>=1.6.0
           - flake8-rst-docstrings
           - pydocstyle
           - pygments

docs/build/unreleased/220.rst

@@ -0,0 +1,6 @@
+.. change::
+    :tags: bug, redis
+    :tickets: 220
+
+    Fixed regression caused by backwards-incompatible API changes in Redis that
+    caused the "distributed lock" feature to not function.

dogpile/cache/backends/memcached.py

@@ -58,7 +58,7 @@ def acquire(self, wait=True):
             elif not wait:
                 return False
             else:
-                sleep_time = (((i + 1) * random.random()) + 2 ** i) / 2.5
+                sleep_time = (((i + 1) * random.random()) + 2**i) / 2.5
                 time.sleep(sleep_time)
             if i < 15:
                 i += 1

dogpile/cache/backends/redis.py

@@ -150,11 +150,13 @@ def _create_client(self):
 
     def get_mutex(self, key):
         if self.distributed_lock:
-            return self.writer_client.lock(
-                "_lock{0}".format(key),
-                timeout=self.lock_timeout,
-                sleep=self.lock_sleep,
-                thread_local=self.thread_local_lock,
+            return _RedisLockWrapper(
+                self.writer_client.lock(
+                    "_lock{0}".format(key),
+                    timeout=self.lock_timeout,
+                    sleep=self.lock_sleep,
+                    thread_local=self.thread_local_lock,
+                )
             )
         else:
             return None
@@ -193,6 +195,22 @@ def delete_multi(self, keys):
         self.writer_client.delete(*keys)
 
 
+class _RedisLockWrapper:
+    __slots__ = ("mutex", "__weakref__")
+
+    def __init__(self, mutex: typing.Any):
+        self.mutex = mutex
+
+    def acquire(self, wait: bool = True) -> typing.Any:
+        return self.mutex.acquire(blocking=wait)
+
+    def release(self) -> typing.Any:
+        return self.mutex.release()
+
+    def locked(self) -> bool:
+        return self.mutex.locked()  # type: ignore
+
+
 class RedisSentinelBackend(RedisBackend):
     """A `Redis <http://redis.io/>`_ backend, using the
     `redis-py <http://pypi.python.org/pypi/redis/>`_ backend.

tox.ini

@@ -39,9 +39,9 @@ deps=
     {memcached}: python-binary-memcached>=0.29.0
     {memcached}: pifpaf>=2.5.0
     {memcached}: pymemcache>=3.5.0
-    {redis}: redis!=4.3.2,!=4.3.3
+    {redis}: redis
     {redis}: pifpaf
-    {redis_sentinel}: redis!=4.3.2,!=4.3.3
+    {redis_sentinel}: redis
     {redis_sentinel}: pifpaf
     {cov}: pytest-cov
 
@@ -83,7 +83,7 @@ deps=
       flake8-rst-docstrings
       # used by flake8-rst-docstrings
       pygments
-      black==21.5b1
+      black==22.3.0
 commands =
     flake8 ./dogpile/ ./tests/ setup.py  {posargs}
     black --check .