[Zope] Migration Strategy

[J. Cameron Cooper]

> We're moving some content from Zope 2.6 to 2.6.2, and I'm wondering 
> what the best way to do this would be.
>
> In the fantasy world that is my mind, I think I'd be looking for a way 
> to safely lock the ZODB in the 2.6 instance, so we can migrate to 
> 2.6.2 while still serving (unchangeable) content from 2.6.

If you have an INSTANCE_HOME setup, you can install the new version 
alongside the old, turn off the old version, change the INSTANCE_HOME 
variable (I actually change a symbolic link under Linux) and turn the 
new one on within whatever time it takes to restart your site.

It you have a ZEO setup, this can be done even faster, possibly 
instantaneously: you could have both new and old running off the same 
ZODB but on different ports, and when you wanted to cut over, make your 
proxy/cache/firewall-port-forwarder point to the new port.

If you're actually talking separate instance (and not just upgrading an 
instance) then you could remove all permissions for changing content 
from whatever roles your usual users have until you've moved everything 
you need to move. But there is no safe low-level way to make the ZODB 
read-only.

          --jcc

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