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Commit d649173c authored by Jim Fulton's avatar Jim Fulton
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Made caches thread safe. In theory, caches are protected by ZEO 

clients, but ZEO clients haven't provided very good protection,
leading to cache corruption.  We'll hopefully fix these client issues,
which cause other problems beside cache corruption, but it seems
prudent to provide low-level cache protection.
parent 8195c421
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Inline Side-by-side
Showing with 98 additions and 20 deletions
src/ZEO/ClientStorage.py
View file @ d649173c
......@@ -338,8 +338,6 @@ class ClientStorage(object):
else:
cache_path = None
self._cache = self.ClientCacheClass(cache_path, size=cache_size)
# TODO: maybe there's a better time to open the cache? Unclear.
self._cache.open()
self._rpc_mgr = self.ConnectionManagerClass(addr, self,
tmin=min_disconnect_poll,
......
src/ZEO/cache.py
View file @ d649173c
......@@ -30,6 +30,7 @@ import BTrees.LOBTree
import logging
import os
import tempfile
import threading
import time
import ZODB.fsIndex
......@@ -121,6 +122,21 @@ ZEC3_HEADER_SIZE = 12
# to the end of the file that the new object can't fit in one
# contiguous chunk, currentofs is reset to ZEC3_HEADER_SIZE first.
class locked(object):
def __init__(self, func):
self.func = func
def __get__(self, inst, class_):
if inst is None:
return self
def call(*args, **kw):
inst._lock.acquire()
try:
return self.func(inst, *args, **kw)
finally:
inst._lock.release()
return call
class ClientCache(object):
"""A simple in-memory cache."""
......@@ -200,6 +216,10 @@ class ClientCache(object):
self._setup_trace(path)
self.open()
self._lock = threading.RLock()
# Backward compatibility. Client code used to have to use the fc
# attr to get to the file cache to get cache stats.
@property
......@@ -353,6 +373,7 @@ class ClientCache(object):
# instance, and also written out near the start of the cache file. The
# new tid must be strictly greater than our current idea of the most
# recent tid.
@locked
def setLastTid(self, tid):
if self.tid is not None and tid <= self.tid:
raise ValueError("new last tid (%s) must be greater than "
......@@ -369,10 +390,11 @@ class ClientCache(object):
# @return a transaction id
# @defreturn string, or None if no transaction is yet known
def getLastTid(self):
if self.tid == z64:
tid = self.tid
if tid == z64:
return None
else:
return self.tid
return tid
##
# Return the current data record for oid and version.
......@@ -382,6 +404,7 @@ class ClientCache(object):
# in the cache
# @defreturn 3-tuple: (string, string, string)
@locked
def load(self, oid, version=""):
ofs = self.current.get(oid)
if ofs is None:
......@@ -414,6 +437,7 @@ class ClientCache(object):
# @return data record, serial number, start tid, and end tid
# @defreturn 4-tuple: (string, string, string, string)
@locked
def loadBefore(self, oid, before_tid):
noncurrent_for_oid = self.noncurrent.get(u64(oid))
if noncurrent_for_oid is None:
......@@ -455,6 +479,7 @@ class ClientCache(object):
# @defreturn string or None
# XXX This approac is wrong, but who cares
@locked
def modifiedInVersion(self, oid):
ofs = self.current.get(oid)
if ofs is None:
......@@ -482,6 +507,7 @@ class ClientCache(object):
# @param data the actual data
# @exception ValueError tried to store non-current version data
@locked
def store(self, oid, version, start_tid, end_tid, data):
# It's hard for the client to avoid storing the same object
# more than once. One case is when the client requests
......@@ -586,6 +612,7 @@ class ClientCache(object):
# @param tid the id of the transaction that wrote a new revision of oid,
# or None to forget all cached info about oid (version, current
# revision, and non-current revisions)
@locked
def invalidate(self, oid, version, tid):
if tid > self.tid and tid is not None:
self.setLastTid(tid)
......@@ -630,16 +657,24 @@ class ClientCache(object):
seek = self.f.seek
read = self.f.read
for oid, ofs in self.current.iteritems():
self._lock.acquire()
try:
seek(ofs)
assert read(1) == 'a', (ofs, self.f.tell(), oid)
size, saved_oid, tid, end_tid, lver = unpack(">I8s8s8sh", read(30))
size, saved_oid, tid, end_tid, lver = unpack(
">I8s8s8sh", read(30))
assert saved_oid == oid, (ofs, self.f.tell(), oid, saved_oid)
assert end_tid == z64, (ofs, self.f.tell(), oid)
if lver:
version = read(lver)
else:
version = ''
yield oid, tid, version
result = oid, tid, version
finally:
self._lock.release()
yield result
def dump(self):
from ZODB.utils import oid_repr
......
src/ZEO/tests/test_cache.py
View file @ d649173c
......@@ -35,7 +35,6 @@ class CacheTests(unittest.TestCase):
# testSerialization reads the entire file into a string, it's not
# good to leave it that big.
self.cache = ZEO.cache.ClientCache(size=1024**2)
self.cache.open()
def tearDown(self):
if self.cache.path:
......@@ -142,7 +141,6 @@ class CacheTests(unittest.TestCase):
dst.write(src.read(self.cache.maxsize))
dst.close()
copy = ZEO.cache.ClientCache(path)
copy.open()
# Verify that internals of both objects are the same.
# Could also test that external API produces the same results.
......@@ -158,7 +156,6 @@ class CacheTests(unittest.TestCase):
if self.cache.path:
os.remove(self.cache.path)
cache = ZEO.cache.ClientCache(size=50)
cache.open()
# We store an object that is a bit larger than the cache can handle.
cache.store(n1, '', n2, None, "x"*64)
......@@ -174,7 +171,6 @@ class CacheTests(unittest.TestCase):
if self.cache.path:
os.remove(self.cache.path)
cache = ZEO.cache.ClientCache(size=50)
cache.open()
# We store an object that is a bit larger than the cache can handle.
cache.store(n1, '', n2, n3, "x"*64)
......@@ -218,7 +214,6 @@ __test__ = dict(
... _ = os.spawnl(os.P_WAIT, sys.executable, sys.executable, 't')
... if os.path.exists('cache'):
... cache = ZEO.cache.ClientCache('cache')
... cache.open()
... cache.close()
... os.remove('cache')
... os.remove('cache.lock')
......@@ -238,7 +233,6 @@ __test__ = dict(
>>> cache.store(ZODB.utils.p64(1), '', ZODB.utils.p64(1), None, data)
>>> cache.close()
>>> cache = ZEO.cache.ClientCache('cache', 1000)
>>> cache.open()
>>> cache.store(ZODB.utils.p64(2), '', ZODB.utils.p64(2), None, 'XXX')
>>> cache.close()
......@@ -254,6 +248,57 @@ __test__ = dict(
LockError: Couldn't lock 'cache.lock'
>>> cache.close()
""",
thread_safe =
r"""
>>> import ZEO.cache, ZODB.utils
>>> cache = ZEO.cache.ClientCache('cache', 1000000)
>>> for i in range(100):
... cache.store(ZODB.utils.p64(i), '', ZODB.utils.p64(1), None, '0')
>>> import random, sys, threading
>>> random = random.Random(0)
>>> stop = False
>>> read_failure = None
>>> def read_thread():
... def pick_oid():
... return ZODB.utils.p64(random.randint(0,99))
...
... try:
... while not stop:
... cache.load(pick_oid())
... cache.loadBefore(pick_oid(), ZODB.utils.p64(2))
... cache.modifiedInVersion(pick_oid())
... except:
... global read_failure
... read_failure = sys.exc_info()
>>> thread = threading.Thread(target=read_thread)
>>> thread.start()
>>> for tid in range(2,10):
... for oid in range(100):
... oid = ZODB.utils.p64(oid)
... cache.invalidate(oid, '', ZODB.utils.p64(tid))
... cache.store(oid, '', ZODB.utils.p64(tid), None, str(tid))
>>> stop = True
>>> thread.join()
>>> if read_failure:
... print 'Read failure:'
... import traceback
... traceback.print_exception(*read_failure)
>>> expected = '9', ZODB.utils.p64(9), ''
>>> for oid in range(100):
... loaded = cache.load(ZODB.utils.p64(oid))
... if loaded != expected:
... print oid, loaded
""",
)
......
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