[Zope] conflicts, sessions, and programming best practices guidelines

[Chris McDonough]

On Nov 16, 2005, at 6:18 PM, Dennis Allison wrote:

>
> Chris,
>
> I am aware that using ZEO to back session database is likely to  
> increase
> the opportunity for conflicts, but using a single session database  
> seems
> to be reaquired if you want, as we do, to distribute out interactive
> application acrosss a cluster of processors cleanly.
>
> Under our current approach, we have multiple Zopes running on multiple
> machines, all referencing a shared database of session variables.
> This allows a HTTP request to be blindly distributed to any of the
> machines.  Given the conflict problems, we may need to rethink this
> simplistic architecture.

Sure.  The alternative solutions are:

- "session affinity" load balancing solutions which always send the  
user to the
   same appserver instance across some number of requests based on a  
cookie value or
   the remote IP address.

- session data manager implementations that don't use ZODB.  Tres  
Seaver coded
   up a drop-in SDM implementation that used MySQL although I'm not  
sure that it
   was able to be released OSS at the time.  A quick Google search  
doesn't turn
   up anything, so it's hard to tell.

- C