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Kirill Smelkov
ZEO
Commits
ed2b7417
Commit
ed2b7417
authored
Sep 02, 2010
by
Jim Fulton
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Added new APIs to check to make sure data read is up to date when used
to decide how to write other data.
parent
f2653e8a
Changes
3
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3 changed files
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186 additions
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0 deletions
+186
-0
src/ZODB/Connection.py
src/ZODB/Connection.py
+18
-0
src/ZODB/interfaces.py
src/ZODB/interfaces.py
+24
-0
src/ZODB/tests/testConnection.py
src/ZODB/tests/testConnection.py
+144
-0
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src/ZODB/Connection.py
View file @
ed2b7417
...
...
@@ -134,6 +134,10 @@ class Connection(ExportImport, object):
# of this list are either in _cache or in _added.
self
.
_registered_objects
=
[]
# ids and serials of objects for which readCurrent was called
# in a transaction.
self
.
_readCurrent
=
{}
# Dict of oid->obj added explicitly through add(). Used as a
# preliminary cache until commit time when objects are all moved
# to the real _cache. The objects are moved to _creating at
...
...
@@ -552,6 +556,10 @@ class Connection(ExportImport, object):
else
:
self
.
_commit
(
transaction
)
for
oid
,
serial
in
self
.
_readCurrent
.
iteritems
():
self
.
_storage
.
checkCurrentSerialInTransaction
(
oid
,
serial
,
transaction
)
def
_commit
(
self
,
transaction
):
"""Commit changes to an object"""
...
...
@@ -674,6 +682,11 @@ class Connection(ExportImport, object):
self
.
_handle_serial
(
oid
,
s
)
def
_handle_serial
(
self
,
oid
,
serial
,
change
=
True
):
# if we write an object, we don't want to check if it was read
# while current. This is a convenient choke point to do this.
self
.
_readCurrent
.
pop
(
oid
,
None
)
if
not
serial
:
return
if
not
isinstance
(
serial
,
str
):
...
...
@@ -782,6 +795,7 @@ class Connection(ExportImport, object):
# pending invalidations regardless. Of course this should only be
# called at transaction boundaries.
def
_storage_sync
(
self
,
*
ignored
):
self
.
_readCurrent
.
clear
()
sync
=
getattr
(
self
.
_storage
,
'sync'
,
0
)
if
sync
:
sync
()
...
...
@@ -949,6 +963,10 @@ class Connection(ExportImport, object):
if
obj
is
not
None
:
self
.
_registered_objects
.
append
(
obj
)
def
readCurrent
(
self
,
ob
):
assert
ob
.
_p_jar
is
self
assert
ob
.
_p_oid
is
not
None
and
ob
.
_p_serial
is
not
None
self
.
_readCurrent
[
ob
.
_p_oid
]
=
ob
.
_p_serial
# persistent.interfaces.IPersistentDatamanager
##########################################################################
...
...
src/ZODB/interfaces.py
View file @
ed2b7417
...
...
@@ -286,6 +286,14 @@ class IConnection(Interface):
begins or until the connection os reopned.
"""
def
readCurrent
(
obj
):
"""Make sure an object being read is current
This is used when applications want to ensure a higher level
of consistency for some operations. This should be called when
an object is read and the information read is used to write a
separate object.
"""
class
IStorageWrapper
(
Interface
):
"""Storage wrapper interface
...
...
@@ -1119,6 +1127,22 @@ class IExternalGC(IStorage):
commit.
"""
class
ReadVerifyingStorage
(
IStorage
):
def
checkCurrentSerialInTransaction
(
oid
,
serial
,
transaction
):
"""Check whether the given serial number is current.
The method is called during the first phase of 2-phase commit
to verify that data read in a transaction is current.
The storage should raise a ReadConflictError if the serial is not
current, although it may raise the exception later, in a call
to store or in a call to tpc_vote.
If no exception is raised, then the serial must remain current
through the end of the transaction.
"""
class
IBlob
(
Interface
):
"""A BLOB supports efficient handling of large data within ZODB."""
...
...
src/ZODB/tests/testConnection.py
View file @
ed2b7417
...
...
@@ -611,6 +611,150 @@ See https://bugs.launchpad.net/zodb/+bug/185066
"""
def
readCurrent
():
r"""
The connection's readCurrent method is called to provide a higher
level of consistency in cases where an object if read to compute an
update to a separate object. When this is used, the
checkCurrentSerialInTransaction method on the storage is called in
2-phase commit.
To demonstrate this, we'll create a storage and give it a test
implementation of checkCurrentSerialInTransaction.
>>> import ZODB.MappingStorage
>>> store = ZODB.MappingStorage.MappingStorage()
>>> from ZODB.POSException import ReadConflictError
>>> bad = set()
>>> def checkCurrentSerialInTransaction(oid, serial, trans):
... print 'checkCurrentSerialInTransaction', `oid`
... if not trans == transaction.get(): print 'oops'
... if oid in bad:
... raise ReadConflictError(oid=oid)
>>> store.checkCurrentSerialInTransaction = checkCurrentSerialInTransaction
Now, we'll use the storage as usual. checkCurrentSerialInTransaction
won't normally be called:
>>> db = ZODB.DB(store)
>>> conn = db.open()
>>> conn.root.a = ZODB.tests.util.P('a')
>>> conn.root.b = ZODB.tests.util.P('b')
>>> transaction.commit()
If we call readCurrent for an object and we modify another object,
then checkCurrentSerialInTransaction will be called for the object
readCurrent was called on.
>>> conn.readCurrent(conn.root.a)
>>> conn.root.b.x = 0
>>> transaction.commit()
checkCurrentSerialInTransaction '\x00\x00\x00\x00\x00\x00\x00\x01'
It doesn't matter how often we call readCurrent,
checkCurrentSerialInTransaction will be called only once:
>>> conn.readCurrent(conn.root.a)
>>> conn.readCurrent(conn.root.a)
>>> conn.readCurrent(conn.root.a)
>>> conn.readCurrent(conn.root.a)
>>> conn.root.b.x += 1
>>> transaction.commit()
checkCurrentSerialInTransaction '\x00\x00\x00\x00\x00\x00\x00\x01'
checkCurrentSerialInTransaction won't be called if another object
isn't modified:
>>> conn.readCurrent(conn.root.a)
>>> transaction.commit()
Or if the object it was called on is modified:
>>> conn.readCurrent(conn.root.a)
>>> conn.root.a.x = 0
>>> conn.root.b.x += 1
>>> transaction.commit()
If the storage raises a conflict error, it'll be propigated:
>>> bad.add(conn.root.a._p_oid)
>>> conn.readCurrent(conn.root.a)
>>> conn.root.b.x += 1
>>> transaction.commit()
Traceback (most recent call last):
...
ReadConflictError: database read conflict error (oid 0x01)
>>> transaction.abort()
The storage may raise it later:
>>> def checkCurrentSerialInTransaction(oid, serial, trans):
... if not trans == transaction.get(): print 'oops'
... print 'checkCurrentSerialInTransaction', `oid`
... store.badness = ReadConflictError(oid=oid)
>>> def tpc_vote(t):
... if store.badness:
... badness = store.badness
... store.badness = None
... raise badness
>>> store.checkCurrentSerialInTransaction = checkCurrentSerialInTransaction
>>> store.badness = None
>>> store.tpc_vote = tpc_vote
It will still be propigated:
>>> conn.readCurrent(conn.root.a)
>>> conn.root.b.x = +1
>>> transaction.commit()
Traceback (most recent call last):
...
ReadConflictError: database read conflict error (oid 0x01)
>>> transaction.abort()
Read checks don't leak accross transactions:
>>> conn.readCurrent(conn.root.a)
>>> transaction.commit()
>>> conn.root.b.x = +1
>>> transaction.commit()
Read checks to work accross savepoints.
>>> conn.readCurrent(conn.root.a)
>>> conn.root.b.x = +1
>>> _ = transaction.savepoint()
>>> transaction.commit()
Traceback (most recent call last):
...
ReadConflictError: database read conflict error (oid 0x01)
>>> transaction.abort()
>>> conn.readCurrent(conn.root.a)
>>> _ = transaction.savepoint()
>>> conn.root.b.x = +1
>>> transaction.commit()
Traceback (most recent call last):
...
ReadConflictError: database read conflict error (oid 0x01)
>>> transaction.abort()
"""
# check interaction w savepoint
# check call in read-only trans followed by write trans
class
_PlayPersistent
(
Persistent
):
def
setValueWithSize
(
self
,
size
=
0
):
self
.
value
=
size
*
' '
__init__
=
setValueWithSize
...
...
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