> what is the Memcache solution and do you have a setup guide?

See https://wiki.jasig.org/display/CASUM/MemcacheTicketRegistry.  I'll
discuss briefly what's _not_ in the manual.  I think there's some
misinformation in the community, borne out in list discussions and
other venues, about the need for the repcache patches to memcached for
clustering.  I think repcache is absolutely unnecessary based on the
failure mode of memcached.  Consider a memcached cluster of 3 nodes,
all noted in the CAS configuration.  The Java memcached client will
calculate a key and store it on one node.  If that node goes down, the
client will attempt to retrieve the key from the dead node and fail,
returning an empty value.  That will appear to CAS and ultimately the
user that he or she is unauthenticated and will simply need to
reauthenticate.  Upon reauthentication the client will know that there
are only two nodes remaining, and calculate a new key that will be
stored on one of the two available nodes and proceed as normal.  That
is a _very_ graceful failure mode in my opinion, and there's no need
for anything additional like repcached.

> Is one solution favourable over another?

Most folks choose based on experience with a particular technology.
We use JpaTicketRegistry on PostgreSQL in production, but I'd be happy
to switch to memcached if needed.  I personally think Terracotta,
JBossCache, and Infinispan are interesting technologies that are
overkill for CAS.  The complexity is not worth the benefits.  That is
absolutely a personal opinion and lots of folks would disagree.

M

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