Commit b5895a5c authored by Julien Muchembled's avatar Julien Muchembled Committed by GitHub

mvccadapter: fix race with invalidations when starting a new transaction (#291)

Fixes #290
parent 12b52a71
...@@ -5,6 +5,11 @@ ...@@ -5,6 +5,11 @@
5.6.0 (unreleased) 5.6.0 (unreleased)
================== ==================
- Fix race with invalidations when starting a new transaction. The bug
affected Storage implementations that rely on mvccadapter, and could result
in data corruption (oid loaded at wrong serial after a concurrent commit).
See `issue 290 <https://github.com/zopefoundation/ZODB/issues/290>`_.
- Improve volatile attribute ``_v_`` documentation. - Improve volatile attribute ``_v_`` documentation.
- Make repozo's recover mode atomic by recovering the backup in a - Make repozo's recover mode atomic by recovering the backup in a
......
...@@ -113,15 +113,15 @@ def pack_with_repeated_blob_records(): ...@@ -113,15 +113,15 @@ def pack_with_repeated_blob_records():
fixed by the time you read this, but there might still be fixed by the time you read this, but there might still be
transactions in the wild that have duplicate records. transactions in the wild that have duplicate records.
>>> fs = ZODB.FileStorage.FileStorage('t', blob_dir='bobs') >>> db = ZODB.DB(ZODB.FileStorage.FileStorage('t', blob_dir='bobs'))
>>> db = ZODB.DB(fs)
>>> conn = db.open() >>> conn = db.open()
>>> conn.root()[1] = ZODB.blob.Blob() >>> conn.root()[1] = ZODB.blob.Blob()
>>> transaction.commit() >>> transaction.commit()
>>> tm = transaction.TransactionManager() >>> tm = transaction.TransactionManager()
>>> oid = conn.root()[1]._p_oid >>> oid = conn.root()[1]._p_oid
>>> from ZODB.utils import load_current >>> fs = db._mvcc_storage.new_instance()
>>> blob_record, oldserial = load_current(fs, oid) >>> _ = fs.poll_invalidations()
>>> blob_record, oldserial = fs.load(oid)
Now, create a transaction with multiple saves: Now, create a transaction with multiple saves:
......
...@@ -49,6 +49,7 @@ class MVCCAdapter(Base): ...@@ -49,6 +49,7 @@ class MVCCAdapter(Base):
instance = MVCCAdapterInstance(self) instance = MVCCAdapterInstance(self)
with self._lock: with self._lock:
self._instances.add(instance) self._instances.add(instance)
instance._lastTransaction()
return instance return instance
def before_instance(self, before=None): def before_instance(self, before=None):
...@@ -77,13 +78,13 @@ class MVCCAdapter(Base): ...@@ -77,13 +78,13 @@ class MVCCAdapter(Base):
def invalidate(self, transaction_id, oids): def invalidate(self, transaction_id, oids):
with self._lock: with self._lock:
for instance in self._instances: for instance in self._instances:
instance._invalidate(oids) instance._invalidate(transaction_id, oids)
def _invalidate_finish(self, oids, committing_instance): def _invalidate_finish(self, tid, oids, committing_instance):
with self._lock: with self._lock:
for instance in self._instances: for instance in self._instances:
if instance is not committing_instance: if instance is not committing_instance:
instance._invalidate(oids) instance._invalidate(tid, oids)
references = serialize.referencesf references = serialize.referencesf
transform_record_data = untransform_record_data = lambda self, data: data transform_record_data = untransform_record_data = lambda self, data: data
...@@ -98,14 +99,26 @@ class MVCCAdapterInstance(Base): ...@@ -98,14 +99,26 @@ class MVCCAdapterInstance(Base):
'checkCurrentSerialInTransaction', 'tpc_abort', 'checkCurrentSerialInTransaction', 'tpc_abort',
) )
_start = None # Transaction start time
_ltid = None # Last storage transaction id
def __init__(self, base): def __init__(self, base):
self._base = base self._base = base
Base.__init__(self, base._storage) Base.__init__(self, base._storage)
self._lock = Lock() self._lock = Lock()
self._invalidations = set() self._invalidations = set()
self._start = None # Transaction start time
self._sync = getattr(self._storage, 'sync', lambda : None) self._sync = getattr(self._storage, 'sync', lambda : None)
def _lastTransaction(self):
ltid = self._storage.lastTransaction()
# At this precise moment, a transaction may be
# committed and we have already received the new tid.
with self._lock:
# So make sure we won't override with a smaller value.
if self._ltid is None:
# Calling lastTransaction() here could result in a deadlock.
self._ltid = ltid
def release(self): def release(self):
self._base._release(self) self._base._release(self)
...@@ -115,8 +128,9 @@ class MVCCAdapterInstance(Base): ...@@ -115,8 +128,9 @@ class MVCCAdapterInstance(Base):
with self._lock: with self._lock:
self._invalidations = None self._invalidations = None
def _invalidate(self, oids): def _invalidate(self, tid, oids):
with self._lock: with self._lock:
self._ltid = tid
try: try:
self._invalidations.update(oids) self._invalidations.update(oids)
except AttributeError: except AttributeError:
...@@ -128,8 +142,8 @@ class MVCCAdapterInstance(Base): ...@@ -128,8 +142,8 @@ class MVCCAdapterInstance(Base):
self._sync() self._sync()
def poll_invalidations(self): def poll_invalidations(self):
self._start = p64(u64(self._storage.lastTransaction()) + 1)
with self._lock: with self._lock:
self._start = p64(u64(self._ltid) + 1)
if self._invalidations is None: if self._invalidations is None:
self._invalidations = set() self._invalidations = set()
return None return None
...@@ -175,7 +189,8 @@ class MVCCAdapterInstance(Base): ...@@ -175,7 +189,8 @@ class MVCCAdapterInstance(Base):
self._modified = None self._modified = None
def invalidate_finish(tid): def invalidate_finish(tid):
self._base._invalidate_finish(modified, self) self._base._invalidate_finish(tid, modified, self)
self._ltid = tid
func(tid) func(tid)
return self._storage.tpc_finish(transaction, invalidate_finish) return self._storage.tpc_finish(transaction, invalidate_finish)
...@@ -260,7 +275,7 @@ class UndoAdapterInstance(Base): ...@@ -260,7 +275,7 @@ class UndoAdapterInstance(Base):
def tpc_finish(self, transaction, func = lambda tid: None): def tpc_finish(self, transaction, func = lambda tid: None):
def invalidate_finish(tid): def invalidate_finish(tid):
self._base._invalidate_finish(self._undone, None) self._base._invalidate_finish(tid, self._undone, None)
func(tid) func(tid)
self._storage.tpc_finish(transaction, invalidate_finish) self._storage.tpc_finish(transaction, invalidate_finish)
...@@ -14,6 +14,7 @@ ...@@ -14,6 +14,7 @@
"""Unit tests for the Connection class.""" """Unit tests for the Connection class."""
from __future__ import print_function from __future__ import print_function
from contextlib import contextmanager
import doctest import doctest
import re import re
import six import six
...@@ -535,13 +536,13 @@ class InvalidationTests(unittest.TestCase): ...@@ -535,13 +536,13 @@ class InvalidationTests(unittest.TestCase):
>>> mvcc_storage.invalidate(p64(1), {p1._p_oid: 1}) >>> mvcc_storage.invalidate(p64(1), {p1._p_oid: 1})
Transaction start times are based on storage's last Transaction start times are based on storage's last transaction,
transaction. (Previousely, they were based on the first which is known from invalidations. (Previousely, they were
invalidation seen in a transaction.) based on the first invalidation seen in a transaction.)
>>> mvcc_instance.poll_invalidations() == [p1._p_oid] >>> mvcc_instance.poll_invalidations() == [p1._p_oid]
True True
>>> mvcc_instance._start == p64(u64(db.storage.lastTransaction()) + 1) >>> mvcc_instance._start == p64(2)
True True
>>> mvcc_storage.invalidate(p64(10), {p2._p_oid: 1, p64(76): 1}) >>> mvcc_storage.invalidate(p64(10), {p2._p_oid: 1, p64(76): 1})
...@@ -570,6 +571,36 @@ class InvalidationTests(unittest.TestCase): ...@@ -570,6 +571,36 @@ class InvalidationTests(unittest.TestCase):
>>> db.close() >>> db.close()
""" """
def test_mvccadapterNewTransactionVsInvalidations(self):
"""
Check that polled invalidations are consistent with the TID at which
the transaction operates. Otherwise, it's like we miss invalidations.
"""
db = databaseFromString("<zodb>\n<mappingstorage/>\n</zodb>")
try:
t1 = transaction.TransactionManager()
c1 = db.open(t1)
r1 = c1.root()
r1['a'] = 1
t1.commit()
t2 = transaction.TransactionManager()
c2 = db.open(t2)
c2.root()['b'] = 1
s1 = c1._storage
l1 = s1._lock
@contextmanager
def beforeLock1():
s1._lock = l1
t2.commit()
with l1:
yield
s1._lock = beforeLock1()
t1.begin()
self.assertIs(s1._lock, l1)
self.assertIn('b', r1)
finally:
db.close()
def doctest_invalidateCache(): def doctest_invalidateCache():
"""The invalidateCache method invalidates a connection's cache. """The invalidateCache method invalidates a connection's cache.
...@@ -1395,4 +1426,5 @@ def test_suite(): ...@@ -1395,4 +1426,5 @@ def test_suite():
s.addTest(doctest.DocTestSuite(checker=checker)) s.addTest(doctest.DocTestSuite(checker=checker))
s.addTest(unittest.makeSuite(TestConnection)) s.addTest(unittest.makeSuite(TestConnection))
s.addTest(unittest.makeSuite(EstimatedSizeTests)) s.addTest(unittest.makeSuite(EstimatedSizeTests))
s.addTest(unittest.makeSuite(InvalidationTests))
return s return s
...@@ -85,13 +85,14 @@ storage has seen. ...@@ -85,13 +85,14 @@ storage has seen.
>>> cn = db.open() >>> cn = db.open()
>>> cn._storage._start == p64(u64(st.lastTransaction()) + 1) >>> ltid = u64(st.lastTransaction())
>>> cn._storage._start == p64(ltid + 1)
True True
>>> cn.db()._mvcc_storage.invalidate(100, dict.fromkeys([1, 2])) >>> cn.db()._mvcc_storage.invalidate(p64(ltid+100), dict.fromkeys([1, 2]))
>>> cn._storage._start == p64(u64(st.lastTransaction()) + 1) >>> cn._storage._start == p64(ltid + 1)
True True
>>> cn.db()._mvcc_storage.invalidate(200, dict.fromkeys([1, 2])) >>> cn.db()._mvcc_storage.invalidate(p64(ltid+200), dict.fromkeys([1, 2]))
>>> cn._storage._start == p64(u64(st.lastTransaction()) + 1) >>> cn._storage._start == p64(ltid + 1)
True True
A connection's high-water mark is set to the transaction id taken from A connection's high-water mark is set to the transaction id taken from
...@@ -105,7 +106,7 @@ but that doesn't work unless an object is modified. sync() will abort ...@@ -105,7 +106,7 @@ but that doesn't work unless an object is modified. sync() will abort
a transaction and process invalidations. a transaction and process invalidations.
>>> cn.sync() >>> cn.sync()
>>> cn._storage._start == p64(u64(st.lastTransaction()) + 1) >>> cn._storage._start == p64(ltid + 201)
True True
Basic functionality Basic functionality
......
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