On Wed, Jan 05, 2011 at 08:24:56PM +0200, Marius Gedminas wrote: > Is anyone using RAMSessionDataContainer? I've a suspicion that it is > utterly broken with modern ZODB versions. > > If I'm not mistaken, MVCC requires you to either call connection.sync() > or open a new connection for every request -- otherwise MVCC > invalidations don't get processed and you always see old versions of > cached objects. > > RAMSessionDataContainer keeps an open connection for every thread, and > that connection is never closed, never synced.
And that's fine, since Connection had afterTransaction and
newTransaction hooks which perform a MVCC sync on transaction
boundaries. I missed that when I was reading the source the first time.
Now I've no explanation at all for these:
> 2011-01-05T10:42:21 WARNING ZopePublication Competing writes/reads at {URL}:
> database conflict error (oid 0x54, class BTrees.OOBTree.OOBTree, serial this
> txn started with 0x038b65ac32bee222 2011-01-05 15:40:11.893509, serial
> currently committed 0x038b65ae561f1999 2011-01-05 15:42:20.184723)
> ------
> 2011-01-05T10:42:21 WARNING ZopePublication Competing writes/reads at {URL}:
> database conflict error (oid 0x54, class BTrees.OOBTree.OOBTree, serial this
> txn started with 0x038b65ac32bee222 2011-01-05 15:40:11.893509, serial
> currently committed 0x038b65ae561f1999 2011-01-05 15:42:20.184723)
> ------
> 2011-01-05T10:42:21 WARNING ZopePublication Competing writes/reads at {URL}:
> database conflict error (oid 0x54, class BTrees.OOBTree.OOBTree, serial this
> txn started with 0x038b65ac32bee222 2011-01-05 15:40:11.893509, serial
> currently committed 0x038b65ae561f1999 2011-01-05 15:42:20.184723)
> ------
> 2011-01-05T10:42:21 WARNING ZopePublication Competing writes/reads at {URL}:
> database conflict error (oid 0x54, class BTrees.OOBTree.OOBTree, serial this
> txn started with 0x038b65ac32bee222 2011-01-05 15:40:11.893509, serial
> currently committed 0x038b65ae561f1999 2011-01-05 15:42:20.184723)
> ------
> 2011-01-05T10:42:21 ERROR SiteError {URL}
> Traceback (most recent call last):
> File
> "/home/zope/eggs/zope.publisher-3.12.4-py2.6.egg/zope/publisher/publish.py",
> line 137, in publish
> publication.afterCall(request, obj)
> File
> "/home/zope/eggs/zope.app.publication-3.12.0-py2.6.egg/zope/app/publication/browser.py",
> line 48, in afterCall
> super(BrowserPublication, self).afterCall(request, ob)
> File
> "/home/zope/eggs/zope.app.publication-3.12.0-py2.6.egg/zope/app/publication/zopepublication.py",
> line 215, in afterCall
> txn.commit()
> File
> "/home/zope/eggs/transaction-1.1.1-py2.6.egg/transaction/_transaction.py",
> line 329, in commit
> self._commitResources()
> File
> "/home/zope/eggs/transaction-1.1.1-py2.6.egg/transaction/_transaction.py",
> line 443, in _commitResources
> rm.commit(self)
> File "/home/zope/eggs/ZODB3-3.9.7-py2.6-linux-i686.egg/ZODB/Connection.py",
> line 566, in commit
> self._commit(transaction)
> File "/home/zope/eggs/ZODB3-3.9.7-py2.6-linux-i686.egg/ZODB/Connection.py",
> line 614, in _commit
> self._store_objects(ObjectWriter(obj), transaction)
> File "/home/zope/eggs/ZODB3-3.9.7-py2.6-linux-i686.egg/ZODB/Connection.py",
> line 666, in _store_objects
> s = self._storage.store(oid, serial, p, '', transaction)
> File "/home/zope/eggs/ZODB3-3.9.7-py2.6-linux-i686.egg/ZODB/utils.py", line
> 255, in __call__
> return func(*args, **kw)
> File
> "/home/zope/eggs/ZODB3-3.9.7-py2.6-linux-i686.egg/ZODB/MappingStorage.py",
> line 258, in store
> oid=oid, serials=(old_tid, serial), data=data)
> ConflictError: database conflict error (oid 0x54, class
> BTrees.OOBTree.OOBTree, serial this txn started with 0x038b65ac32bee222
> 2011-01-05 15:40:11.893509, serial currently committed 0x038b65ae561f1999
> 2011-01-05 15:42:20.184723)
>
> Note how "serial this txn started with" doesn't change in all the
> retries.
Any ideas?
Marius Gedminas
--
http://pov.lt/ -- Zope 3/BlueBream consulting and development
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