[Zope-dev] Racks and ZEO (was Alternative Storages)

[Phillip J. Eby]

At 03:54 PM 5/4/00 +0000, Jason Spisak wrote:
>
>data that get's huge and changed a lot.  Maybe I'm trying to address an
>issue that gets addressed by ZEO.  Maybe you are not the one to answer
>this, but with Racks and ZEO could I have 2 different Zope installations
>accessing the same Rack for the same object, as long as it's class
>definition was the same?

A Rack lives in a ZODB.  It's just like any other Zope object.  So if it's
in a ZEO, it will be accessible like any other part of the same application.

>For example I have a 2 Squishdots, one is in a
>Zope that has CyberCash in it, and one doesn't.  Can I have the Squishdot's
>using the same Rack for their information?

If they share the same ZODB.  Of course, keep in mind that the Rack may not
store its data in ZODB at all - e.g. an SQL database.  If so, then ZEO is
irrelevant; you can have as many Zopes with copies of that Rack as you
want, all accessing the data, so long as any additional sheets or
attributes also come from shared external sources.


>>Another, related issue is garbage collection, or
>> making sure that objects are deleted in "both" places. 
>
>Doesn't ZEO have a facility for this in it's framework.  Invalidation
>messages etc...?

That's cache invalidation.  Unrelated issue.