> I'd like to see the servers defined in the Service Manager. That way you 
> would have a Service with it's URL, and then (n) servers with their direct 
> URLs.

I'll say again there are fundamental obstacles with this approach.
First, there is the problem that not all load balanced setups allow
direct access to the individual nodes servicing the cluster; for
example, they may be on a private network.  The second and likely more
common problem is one of hostname verification.  Even if the nodes are
accessible, the CN of the SSL certificate on the virtual IP is almost
certainly different from the hostnames of the individual nodes, e.g.
https://service.vt.edu maps to https://service-n.subdomain.vt.edu.
While we could allow pluggable hostname verification strategies on the
server like we do with the Java client, it's yet one more obstacle to
overcome.

> We are doing this now and it's a mess.
> ...
> Right now, we are catching the logout with our load balancer, then re-routing 
> it to a script that replicates it to the servers related to the service.

This is not the strategy we are leaning toward.  (Maybe I described it
poorly in haste.)  We are leaning toward a clustered state store for
the client, e.g. JBossCache, where each node in the cluster consults
the state store to determine the present authenticated state.  When
_any_ node receives the LogoutRequest message, it looks up the entry
in the shared state store and destroys it.  There are some potential
problems in that lookup, but they seem soluble in theory.  Then when
the node holding the session receives its next request from the user,
it checks the shared state store, can't find the entry, and marks the
session as having ended and redirects to CAS for authentication.

> If we could help in some way to get this feature in, please let me know.

I created https://issues.jasig.org/browse/CASC-114 a long time ago to
help get started on a solution for the Java client.  Anyone is welcome
to provide a patch or suggest other implementations.  Maybe we need a
general placeholder CAS Server issue for "Support for Clustered Single
Sign Out".  I don't see such an issue at
https://issues.jasig.org/browse/CAS, but I didn't do an exhaustive
search.

M

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