[ZODB-Dev] ZSS Failover and client caching

[Dyon Balding]

Hi all,

I am in the process of setting up a cluster of machines using ZEO. 
There will be some kind of hardware load balancer in front of the Zope
clients, which will all be connected to the single ZSS.  I need to
formulate a plan in the case of the ZSS server failing.

One option would be to have a backup ZSS that would assume the main
ZSS's IP once it had been taken off the network.  A problem I see with
this is that if the Data.fs on the backup system is out of sync with the
main server, the clients will not realise this because they won't try to
update their local cache unless they get a cache miss.  Obviously
restarting the Zope clients would fix that, but I was hoping for a more
seamless failover.

Another option would be to have a completely separate network of Zope
clients and a ZSS, and just point the load balancer at that if there
were problems with the main network.  This doesn't seem to utilise the
hardware very effectively though.

What are other people using in the case of a ZSS failure in a production
environment?

thanks
-d

-- 
| Dyon Balding . Software Engineer . HiringTools.Monster.com
|   dyon@hiringtools.com . +1 415 288 3375