[Zodb-checkins] CVS: ZODB3/ZEO - ClientStorage.py:1.73.2.25
ClientCache.py:1.38.2.3
Jeremy Hylton
jeremy at zope.com
Thu Jun 12 17:31:21 EDT 2003
Update of /cvs-repository/ZODB3/ZEO
In directory cvs.zope.org:/tmp/cvs-serv25917/ZEO
Modified Files:
Tag: ZODB3-3_1-branch
ClientStorage.py ClientCache.py
Log Message:
Partial replacement fix: Use a lock to serialize load() and tpc_finish().
=== ZODB3/ZEO/ClientStorage.py 1.73.2.24 => 1.73.2.25 ===
--- ZODB3/ZEO/ClientStorage.py:1.73.2.24 Wed Jun 11 19:11:32 2003
+++ ZODB3/ZEO/ClientStorage.py Thu Jun 12 16:31:21 2003
@@ -262,20 +262,14 @@
self._oid_lock = threading.Lock()
self._oids = [] # Object ids retrieved from new_oids()
- # There's a nasty race. The ZRPC layer can deliver invalidations
- # out of order (i.e., the server sends the result of a load, then
- # sends an invalidation for that object, but we see the invalidation
- # first). To worm around this, load() creates a dict in
- # _loading_oid_invs and invalidateTrans() stores any arriving
- # invalidations in that dict. When the zeoLoad() call returns
- # from the server, load() handles the invalidations.
- # It's possible for different threads to attempt to load the same
- # oid at the same time. To account for this, we keep a counter
- # in _loading_oid_count. Invalidations are only handled when
- # the count reaches zero. Mutations of these dicts are protected
- # by _lock.
- self._loading_oid_count = {} # oid -> count of pending load()s
- self._loading_oid_invs = {} # oid -> set of invalidated versions
+ # load() and tpc_finish() must be serialized to guarantee
+ # that cache modifications from each occur atomically.
+ # It also prevents multiple load calls occuring simultaneously,
+ # which simplifies the cache logic.
+ self._load_lock = threading.Lock()
+ # _load_oid and _load_status are protected by _lock
+ self._load_oid = None
+ self._load_status = None
# Can't read data in one thread while writing data
# (tpc_finish) in another thread. In general, the lock
@@ -620,39 +614,36 @@
"""
self._lock.acquire() # for atomic processing of invalidations
try:
- p = self._cache.load(oid, version)
- if p:
- return p
+ pair = self._cache.load(oid, version)
+ if pair:
+ return pair
finally:
self._lock.release()
if self._server is None:
raise ClientDisconnected()
- self._incLoadStatus(oid)
-
+ self._load_lock.acquire()
try:
- p, s, v, pv, sv = self._server.zeoLoad(oid)
- except:
self._lock.acquire()
try:
- self._decLoadStatus(oid)
+ self._load_oid = oid
+ self._load_status = True
finally:
self._lock.release()
- raise
- self._lock.acquire()
- try:
- is_last, invs = self._decLoadStatus(oid)
- if is_last:
- if invs:
- for v in invs:
- self._cache.invalidate(oid, v)
- else:
+ p, s, v, pv, sv = self._server.zeoLoad(oid)
+
+ self._lock.acquire() # for atomic processing of invalidations
+ try:
+ if self._load_status:
self._cache.checkSize(0)
self._cache.store(oid, p, s, v, pv, sv)
+ self._load_oid = None
+ finally:
+ self._lock.release()
finally:
- self._lock.release()
+ self._load_lock.release()
if v and version and v == version:
return pv, sv
@@ -661,42 +652,6 @@
return p, s
raise KeyError, oid # no non-version data for this
- def _incLoadStatus(self, oid):
- """Increment the load count for oid, version pair.
-
- Does its own locking.
- """
- self._lock.acquire()
- try:
- count = self._loading_oid_count.get(oid)
- if count is None:
- count = 0
- self._loading_oid_invs[oid] = {}
- count += 1
- self._loading_oid_count[oid] = count
- finally:
- self._lock.release()
-
- def _decLoadStatus(self, oid):
- """Decrement load count.
-
- Return boolean indicating whether this was the last load and
- a list of versions to invalidate. The list is empty unless
- the boolean is True.
-
- Caller must hold self._lock.
- """
- count = self._loading_oid_count[oid]
- count -= 1
- if count:
- self._loading_oid_count[oid] = count
- return 0, []
- else:
- del self._loading_oid_count[oid]
- d = self._loading_oid_invs[oid]
- del self._loading_oid_invs[oid]
- return 1, d.keys()
-
def modifiedInVersion(self, oid):
"""Storage API: return the version, if any, that modfied an object.
@@ -847,22 +802,22 @@
"""Storage API: finish a transaction."""
if transaction is not self._transaction:
return
+ self._load_lock.acquire()
try:
self._lock.acquire() # for atomic processing of invalidations
try:
self._update_cache()
+ if f is not None:
+ f()
finally:
self._lock.release()
- if f is not None:
- f()
-
self._server.tpc_finish(self._serial)
r = self._check_serials()
assert r is None or len(r) == 0, "unhandled serialnos: %s" % r
-
finally:
+ self._load_lock.release()
self.end_transaction()
def _update_cache(self):
@@ -988,22 +943,11 @@
try:
# versions maps version names to dictionary of invalidations
versions = {}
- for pair in invs:
- oid, version = pair
- d = versions.setdefault(version, {})
- d[oid] = 1
-
- # Update the _loading_oids_invs dict for this oid,
- # if necessary.
- d = self._loading_oid_invs.get(oid)
- if d is not None:
- # load() is waiting for this. Mark the version
- # as invalidated, so that load can invalidate it
- # later.
- d[version] = 1
- else:
- # load() isn't waiting for this. Simply invalidate it.
- self._cache.invalidate(oid, version=version)
+ for oid, version in invs:
+ if oid == self._load_oid:
+ self._load_status = False
+ self._cache.invalidate(oid, version=version)
+ versions.setdefault(version, {})[oid] = 1
if self._db is not None:
for v, d in versions.items():
=== ZODB3/ZEO/ClientCache.py 1.38.2.2 => 1.38.2.3 ===
--- ZODB3/ZEO/ClientCache.py:1.38.2.2 Thu Nov 21 13:58:51 2002
+++ ZODB3/ZEO/ClientCache.py Thu Jun 12 16:31:21 2003
@@ -516,7 +516,26 @@
finally:
self._release()
+ def _get_serial(self, oid):
+ pos = self._get(oid, None)
+ if pos is None:
+ return None
+ f = self._f[pos < 0]
+ # The cache header is 27 bytes long. The last 8 bytes are the
+ # serialno.
+ f.seek(abs(pos) + 19)
+ return f.read(8)
+
def _store(self, oid, p, s, version, pv, sv):
+ # Caller must acquire lock.
+
+ # Make sure the serial number we are writing is greater than
+ # a serial number already in the cache. This is a crucial
+ # invariant for cache consistency.
+ if __debug__:
+ oldserial = self._get_serial(oid)
+ assert oldserial is None or oldserial < (s or sv)
+
if not s:
p = ''
s = '\0\0\0\0\0\0\0\0'
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