From 6448dd833524ac3fc503506b624841c9d642de8a Mon Sep 17 00:00:00 2001
From: Thomas Chaumeny <t.chaumeny@gmail.com>
Date: Sun, 12 Oct 2014 15:37:17 +0200
Subject: [PATCH] Fixed #23642 -- Made LocMemCache.incr() thread-safe as
documented
---
django/core/cache/backends/locmem.py | 25 ++++++++++++++++---------
docs/releases/1.8.txt | 3 ++-
2 files changed, 18 insertions(+), 10 deletions(-)
diff --git a/django/core/cache/backends/locmem.py b/django/core/cache/backends/locmem.py
index 1e8b60544a..edf0ff22a7 100644
--- a/django/core/cache/backends/locmem.py
+++ b/django/core/cache/backends/locmem.py
@@ -1,5 +1,6 @@
"Thread-safe in-memory cache backend."
+from contextlib import contextmanager
import time
try:
from django.utils.six.moves import cPickle as pickle
@@ -17,6 +18,12 @@ _expire_info = {}
_locks = {}
+@contextmanager
+def dummy():
+ """A context manager that does nothing special."""
+ yield
+
+
class LocMemCache(BaseCache):
def __init__(self, name, params):
BaseCache.__init__(self, params)
@@ -34,11 +41,11 @@ class LocMemCache(BaseCache):
return True
return False
- def get(self, key, default=None, version=None):
+ def get(self, key, default=None, version=None, acquire_lock=True):
key = self.make_key(key, version=version)
self.validate_key(key)
pickled = None
- with self._lock.reader():
+ with (self._lock.reader() if acquire_lock else dummy()):
if not self._has_expired(key):
pickled = self._cache[key]
if pickled is not None:
@@ -47,7 +54,7 @@ class LocMemCache(BaseCache):
except pickle.PickleError:
return default
- with self._lock.writer():
+ with (self._lock.writer() if acquire_lock else dummy()):
try:
del self._cache[key]
del self._expire_info[key]
@@ -69,13 +76,13 @@ class LocMemCache(BaseCache):
self._set(key, pickled, timeout)
def incr(self, key, delta=1, version=None):
- value = self.get(key, version=version)
- if value is None:
- raise ValueError("Key '%s' not found" % key)
- new_value = value + delta
- key = self.make_key(key, version=version)
- pickled = pickle.dumps(new_value, pickle.HIGHEST_PROTOCOL)
with self._lock.writer():
+ value = self.get(key, version=version, acquire_lock=False)
+ if value is None:
+ raise ValueError("Key '%s' not found" % key)
+ new_value = value + delta
+ key = self.make_key(key, version=version)
+ pickled = pickle.dumps(new_value, pickle.HIGHEST_PROTOCOL)
self._cache[key] = pickled
return new_value
diff --git a/docs/releases/1.8.txt b/docs/releases/1.8.txt
index 41907634b2..7cdb6aaf77 100644
--- a/docs/releases/1.8.txt
+++ b/docs/releases/1.8.txt
@@ -157,7 +157,8 @@ Minor features
Cache
^^^^^
-* ...
+* The ``incr()`` method of the
+ ``django.core.cache.backends.locmem.LocMemCache`` backend is now thread-safe.
Email
^^^^^