You should be able to arrange to some time in the past. You may need a custom pack script. (I don't remember off hand if zeopack accepts fractional days.) But maybe packing some small time period back (say 1 hour) would work around the issue.
Jim On Fri, Jul 18, 2014 at 10:09 AM, Ian McCracken <i...@zenoss.com> wrote: > We have an area of our product that can, depending on certain conditions, > produce lots of rapid transactions all at once. We’re getting many reports > of POSKeyErrors at sites where the transaction volume is higher than others. > They appear to coincide (in many cases, at least) with zodbpack runs. > > After some investigation, it appears that it’s a timing issue. If an object > is unreferenced during the pre_pack() stage, it will be marked for GC. If it > then becomes referenced before the actual DELETE FROM is executed, it will > be deleted nonetheless and POSKeyErrors will result. > > Now, I don’t know how the object is unreferenced and referenced in separate > transactions; as far as I can tell, there are no two-transaction moves or > anything like that happening. Nonetheless, it’s entirely possible we can > solve this by tracking down the code that sets up the race condition. > > But is there any lower-level way around the race condition? A good amount of > our application is pluggable by the end user, and I’d like to avoid vague > technical warnings about transaction boundaries if possible :) If we could > verify that no POSKeyErrors will result from the DELETE before running it, > that would be much simpler. > > I should also mention that running zodbpack with days=1 isn’t an > across-the-board solution for us. We have some customers for whom rapid > growth of the database is an issue, and they pack more frequently. > > —Ian > > _______________________________________________ > For more information about ZODB, see http://zodb.org/ > > ZODB-Dev mailing list - ZODB-Dev@zope.org > https://mail.zope.org/mailman/listinfo/zodb-dev > -- Jim Fulton http://www.linkedin.com/in/jimfulton _______________________________________________ For more information about ZODB, see http://zodb.org/ ZODB-Dev mailing list - ZODB-Dev@zope.org https://mail.zope.org/mailman/listinfo/zodb-dev
