PANIC during product installation

[Paul Winkler]

Cannot reliably reproduce, but I *occasionally* get a PANIC during zope
startup on certain products - specifically, CMFCalendar.
This is problematic for any server that must be able to
restart unattended.

Possibly related: http://zope.org/Collectors/Zope/300

Further discussion & possible mitigation in this thread:
"ConflictError on CMFCalendar ?"
http://aspn.activestate.com/ASPN/Mail/Message/Zope-CMF/1976604

Traceback is as follows:

------
2004-01-03T06:54:44 ERROR(200) Zope Couldn't install CMFCalendar
Traceback (innermost last):
  File /zope/SoftwareHome/lib/python/OFS/Application.py, line 581, in install_product
    (Object: Zope)
    (Info: CMFCalendar)
  File /zope/SoftwareHome/lib/python/ZODB/Transaction.py, line 177, in commit
  File /zope/SoftwareHome/lib/python/ZODB/Transaction.py, line 344, in _commit_objects
  File /zope/SoftwareHome/lib/python/ZODB/Connection.py, line 300, in commit
ConflictError: database conflict error (oid 0000000000000002, class OFS.Application.Application)
------
2004-01-03T06:54:44 PANIC(300) z2 Startup exception
Traceback (innermost last):
  File /zope/SoftwareHome/z2.py, line 228, in ?
  File /zope/SoftwareHome/lib/python/Zope/__init__.py, line 38, in startup
    (Object: startup)
  File /zope/SoftwareHome/lib/python/Zope/App/startup.py, line 38, in startup
    (Object: ZEO storage at dev-zope-knox01.cti-pet.com 9700)
  File /zope/SoftwareHome/lib/python/OFS/Application.py, line 245, in initialize
    (Object: Zope)
  File /zope/SoftwareHome/lib/python/OFS/Application.py, line 544, in install_products
    (Object: Zope)
  File /zope/SoftwareHome/lib/python/OFS/Application.py, line 581, in install_product
    (Object: Zope)
    (Info: CMFCalendar)
  File /zope/SoftwareHome/lib/python/ZODB/Transaction.py, line 177, in commit
  File /zope/SoftwareHome/lib/python/ZODB/Transaction.py, line 344, in _commit_objects
  File /zope/SoftwareHome/lib/python/ZODB/Connection.py, line 300, in commit
ConflictError: database conflict error (oid 0000000000000002, class OFS.Application.Application)
------

[Paul Winkler (slinkp)]

fyi, this issue is still relevant in Zope 2.7.3.
I got it today with Formulator.

[Paul Winkler (slinkp)]

FWIW, one thing to check if you run into this:
if you are using ZEO and use persistent ZEO cache files, it's possible that your cache files in $INSTANCE_HOME/var/ have gone insane. If they have, delete them and restart. This solved my most recent encounter with conflict errors on startup.

The symptom was this in the ConflictError:
ZODB.POSException.ConflictError: database conflict error (
 serial this txn started with 0x035b25f36751f988 2005-02-10 18:59:24.215675,
 serial currently committed 0x035b743c6d186822 2005-02-24 17:00:25.569220)

... note that this shows a two-week-long transaction, very unlikely and highly suggestive that the ZEO cache is fubar. Thanks to Tim Peters for spotting that.

See this thread on zope-dev: http://mail.zope.org/pipermail/zope-dev/2005-February/024353.html

[Hanno Schlichting (hannosch)]

If you have multiple ZEO clients being restarted at the same time, you need to make sure to disable product installation on all but one of them. In Zope 2.12+ you can usually disable the product installation for all ZEO clients, as there's no code left that relies on this feature. So put "enable-product-installation off" into your zope.conf.