Thanks Arthur!

From your below email, I take some time to learn the link you recommended. 
Looks like there are 3 solutions. All of them have pros and cons. In order to 
achieve high availability (when one server is down, the authentication system 
still works) and scalability (when the user base increases, we could add more 
servers in order to improve authentication performance) goal, which solution do 
you prefer? Or you prefer other solution?

CLUSTERING WITH REPLICATION
We have been struggling to get a clustering with replication environment setup 
using the JBoss Cache solution (JbossCacheTicketRegistry), which was outlined 
in the link you mentioned.  However, there have been some unexpected problems 
maintaining a stable JBoss Cache replication cluster.  Though it is maintained 
by JA-SIG, there aren’t many people you will find that are very experienced 
with it much less managing JBoss Cache; there are a number of people who will 
probably agree with me on that.  Another option for doing clustering with 
replication is to use the MemCacheTicketRegistry available in CAS 3.3.0.  This 
is the option favored by Rutgers, who is the primary maintainer of the CAS code 
base.  Scott B can testify about it being lightweight, however I don’t know 
anyone else that has deployed it in their environments.
CLUSTERING WITHOUT REPLICATION
If you want plain clustering without replication, then you could either go with 
a backend data store holding users SSO information and have the CAS servers be 
dummies by using the JpaTicketRegistry.  This would allow your users to hit any 
of the CAS servers and remove the need for replicating data, however you would 
have a single point of failure (data store).
FAIL OVER
However, most CAS deployments appear to use a active/passive fail over setup 
where you have two deployments and have your load balancer direct traffic to 
the primary and fail over to the secondary when necessary.  This option 
requires little / no major customization.


regards,
George

-----------------------------------------------------------------------------------------------------------------------------------
Message: 11
Date: Tue, 18 Nov 2008 14:27:00 +0100
From: Arthur Erd?s <[EMAIL PROTECTED]>
Subject: Re: high availability issue of CAS
To: Yale CAS mailing list <[email protected]>
Cc: [EMAIL PROTECTED]
Message-ID: <[EMAIL PROTECTED]>
Content-Type: text/plain; charset=utf-8

There has recently been a question concerning CAS load balance /
failover. Take a look at
http://www.nabble.com/Best-practice-for-CAS-load-balance-failover-td19912100.html
 - it might be what you are looking for...

Kind regards,
Arthur


      
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