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Clean up the the locmem cache backend and utils.synch by using contex…
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…t managers. Puch prettier.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@17152 bcc190cf-cafb-0310-a4f2-bffc1f526a37
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@alex
alex committed Nov 27, 2011
1 parent 1086a9a commit e4919f6
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Showing 2 changed files with 43 additions and 55 deletions.
60 changes: 20 additions & 40 deletions django/core/cache/backends/locmem.py
View file
@@ -1,5 +1,7 @@
"Thread-safe in-memory cache backend." "Thread-safe in-memory cache backend."


from __future__ import with_statement

import time import time
try: try:
import cPickle as pickle import cPickle as pickle
Expand All @@ -26,8 +28,7 @@ def __init__(self, name, params):
def add(self, key, value, timeout=None, version=None): def add(self, key, value, timeout=None, version=None):
key = self.make_key(key, version=version) key = self.make_key(key, version=version)
self.validate_key(key) self.validate_key(key)
self._lock.writer_enters() with self._lock.writer():
try:
exp = self._expire_info.get(key) exp = self._expire_info.get(key)
if exp is None or exp <= time.time(): if exp is None or exp <= time.time():
try: try:
Expand All @@ -37,14 +38,11 @@ def add(self, key, value, timeout=None, version=None):
except pickle.PickleError: except pickle.PickleError:
pass pass
return False return False
finally:
self._lock.writer_leaves()


def get(self, key, default=None, version=None): def get(self, key, default=None, version=None):
key = self.make_key(key, version=version) key = self.make_key(key, version=version)
self.validate_key(key) self.validate_key(key)
self._lock.reader_enters() with self._lock.reader():
try:
exp = self._expire_info.get(key) exp = self._expire_info.get(key)
if exp is None: if exp is None:
return default return default
Expand All @@ -54,18 +52,13 @@ def get(self, key, default=None, version=None):
return pickle.loads(pickled) return pickle.loads(pickled)
except pickle.PickleError: except pickle.PickleError:
return default return default
finally: with self._lock.writer():
self._lock.reader_leaves()
self._lock.writer_enters()
try:
try: try:
del self._cache[key] del self._cache[key]
del self._expire_info[key] del self._expire_info[key]
except KeyError: except KeyError:
pass pass
return default return default
finally:
self._lock.writer_leaves()


def _set(self, key, value, timeout=None): def _set(self, key, value, timeout=None):
if len(self._cache) >= self._max_entries: if len(self._cache) >= self._max_entries:
Expand All @@ -78,54 +71,44 @@ def _set(self, key, value, timeout=None):
def set(self, key, value, timeout=None, version=None): def set(self, key, value, timeout=None, version=None):
key = self.make_key(key, version=version) key = self.make_key(key, version=version)
self.validate_key(key) self.validate_key(key)
self._lock.writer_enters() with self._lock.writer():
try: try:
pickled = pickle.dumps(value, pickle.HIGHEST_PROTOCOL) pickled = pickle.dumps(value, pickle.HIGHEST_PROTOCOL)
self._set(key, pickled, timeout) self._set(key, pickled, timeout)
except pickle.PickleError: except pickle.PickleError:
pass pass
finally:
self._lock.writer_leaves()


def incr(self, key, delta=1, version=None): def incr(self, key, delta=1, version=None):
value = self.get(key, version=version) value = self.get(key, version=version)
if value is None: if value is None:
raise ValueError("Key '%s' not found" % key) raise ValueError("Key '%s' not found" % key)
new_value = value + delta new_value = value + delta
key = self.make_key(key, version=version) key = self.make_key(key, version=version)
self._lock.writer_enters() with self._lock.writer():
try: try:
pickled = pickle.dumps(new_value, pickle.HIGHEST_PROTOCOL) pickled = pickle.dumps(new_value, pickle.HIGHEST_PROTOCOL)
self._cache[key] = pickled self._cache[key] = pickled
except pickle.PickleError: except pickle.PickleError:
pass pass
finally:
self._lock.writer_leaves()
return new_value return new_value


def has_key(self, key, version=None): def has_key(self, key, version=None):
key = self.make_key(key, version=version) key = self.make_key(key, version=version)
self.validate_key(key) self.validate_key(key)
self._lock.reader_enters() with self._lock.reader():
try:
exp = self._expire_info.get(key) exp = self._expire_info.get(key)
if exp is None: if exp is None:
return False return False
elif exp > time.time(): elif exp > time.time():
return True return True
finally:
self._lock.reader_leaves()


self._lock.writer_enters() with self._lock.writer():
try:
try: try:
del self._cache[key] del self._cache[key]
del self._expire_info[key] del self._expire_info[key]
except KeyError: except KeyError:
pass pass
return False return False
finally:
self._lock.writer_leaves()


def _cull(self): def _cull(self):
if self._cull_frequency == 0: if self._cull_frequency == 0:
Expand All @@ -148,11 +131,8 @@ def _delete(self, key):
def delete(self, key, version=None): def delete(self, key, version=None):
key = self.make_key(key, version=version) key = self.make_key(key, version=version)
self.validate_key(key) self.validate_key(key)
self._lock.writer_enters() with self._lock.writer():
try:
self._delete(key) self._delete(key)
finally:
self._lock.writer_leaves()


def clear(self): def clear(self):
self._cache.clear() self._cache.clear()
Expand Down
38 changes: 23 additions & 15 deletions django/utils/synch.py
View file
Expand Up @@ -6,12 +6,16 @@
(Contributed to Django by eugene@lazutkin.com) (Contributed to Django by eugene@lazutkin.com)
""" """


from __future__ import with_statement

import contextlib
try: try:
import threading import threading
except ImportError: except ImportError:
import dummy_threading as threading import dummy_threading as threading


class RWLock:
class RWLock(object):
""" """
Classic implementation of reader-writer lock with preference to writers. Classic implementation of reader-writer lock with preference to writers.
Expand All @@ -34,43 +38,41 @@ def __init__(self):
self.waiting_writers = 0 self.waiting_writers = 0


def reader_enters(self): def reader_enters(self):
self.mutex.acquire() with self.mutex:
try:
if self.active_writers == 0 and self.waiting_writers == 0: if self.active_writers == 0 and self.waiting_writers == 0:
self.active_readers += 1 self.active_readers += 1
self.can_read.release() self.can_read.release()
else: else:
self.waiting_readers += 1 self.waiting_readers += 1
finally:
self.mutex.release()
self.can_read.acquire() self.can_read.acquire()


def reader_leaves(self): def reader_leaves(self):
self.mutex.acquire() with self.mutex:
try:
self.active_readers -= 1 self.active_readers -= 1
if self.active_readers == 0 and self.waiting_writers != 0: if self.active_readers == 0 and self.waiting_writers != 0:
self.active_writers += 1 self.active_writers += 1
self.waiting_writers -= 1 self.waiting_writers -= 1
self.can_write.release() self.can_write.release()

@contextlib.contextmanager
def reader(self):
self.reader_enters()
try:
yield
finally: finally:
self.mutex.release() self.reader_leaves()


def writer_enters(self): def writer_enters(self):
self.mutex.acquire() with self.mutex:
try:
if self.active_writers == 0 and self.waiting_writers == 0 and self.active_readers == 0: if self.active_writers == 0 and self.waiting_writers == 0 and self.active_readers == 0:
self.active_writers += 1 self.active_writers += 1
self.can_write.release() self.can_write.release()
else: else:
self.waiting_writers += 1 self.waiting_writers += 1
finally:
self.mutex.release()
self.can_write.acquire() self.can_write.acquire()


def writer_leaves(self): def writer_leaves(self):
self.mutex.acquire() with self.mutex:
try:
self.active_writers -= 1 self.active_writers -= 1
if self.waiting_writers != 0: if self.waiting_writers != 0:
self.active_writers += 1 self.active_writers += 1
Expand All @@ -83,5 +85,11 @@ def writer_leaves(self):
while t > 0: while t > 0:
self.can_read.release() self.can_read.release()
t -= 1 t -= 1

@contextlib.contextmanager
def writer(self):
self.writer_enters()
try:
yield
finally: finally:
self.mutex.release() self.writer_leaves()

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