[ZODB-Dev] DBTab and ZEO Failover

[Shane Hathaway]

Lou Scalpati wrote:
> I have zope 2.6.1 and Zeo 2.02  and DBTab 1.1
> 
> My question is about zeo fallback connections.  I noticed in the dbtab.conf
> file it shows fallbacks for a mount for ZRS.  Does this also apply to other
> zeo servers without ZRS?
>  I have 2 database servers that I am running zeo server on.  If for some
> reason the primary dies will the client time out and go to the secondary if
> it is defined like it shows for ZRS?  or is that a function of additional
> code that ZRS introduces?  If that will work is there a maximum number of
> fallback servers it can address?  Is this method reliable or am I better off
> using another failover strategy such as ipvs in front of the zeo servers.

Yes, you can reliably use this as a fallback mechanism if you have some 
way to keep the secondaries in sync with the primary.  ZRS does this in 
real time.  I don't know whether it would be safe to fail over to a 
secondary that is out of date.

Note that DBTab has little to do with this--DBTab just lets you enable 
fallback, but ZEO does all the work.

Shane