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

[Jason Spisak]

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.

You're previous post enlightened me in this respect.

> 
> >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.
> 

This is the best argument for keeping you data in an SQL database I've seen
yet.  I would love to see that hold true for FileStorage, and something
that doesn't have the DB overhead.  Just to have a choice.

> 
> >>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.
>

Righty-o. 

Thanks again for taking you time to clear some things up.  I really
appreciate it.

All my best,


Jason Spisak
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