[Zope-CMF] Re: migration.

[Shane Hathaway]

Lucas Hofman wrote:
> Good to hear that you also have had a migration project. Are there any
> lessons to be learned from the migration of the dogbowl that might be
> worthwhile to the developer community?

Not directly related to migration, but...

cmf.zope.org is running a similar setup as www.zope.org, with a load
balancer and two ZEO clients.  To perform the migration, I decided to
create a personal ZEO client on a different box so that there would be
no interruption.  However, it turns out to be *extremely* important you
run exactly the same version of Zope on all ZEO clients.  I didn't know
it was different and very strange things happened.  I hope it's cleaned
up now.  For multiple versions to work simultaneously, the code would
have to be both backward and forward compatible.

I ran the migrate_ptk script from the latest CVS checkout and it worked
quite well, except that the catalog didn't appear to be updated.  It
took me a long time to figure out that multiple simultaneous Zope
versions were causing the problem.  Were it not for that, it would have
happened flawlessly.  Oh to eliminate human error. :-)

The only other issue is that for some reason the discussions didn't get
migrated correctly.  The script apparently has a flaw.  I wrote another
script designed to fix just that problem in place, but it ended up
wiping out some old discussions somehow anyway. :-/

In the future, when the name of a Python package is changed (in Zope in
general), I think the right thing to do will be to first migrate class
instances in place without changing *anything else* in the classes,
*then* change the classes.

Shane