high availability referrals

[Mike Jackson <jacksonm@isorauta.ntc.nokia.com>]

Hi,
 I will explain a problem below and hope that somebody here has a good
solution about high availability of referred DIT namespace portions.


				LDAP Master - ldap-1.foo.com

				dc=foo,dc=com
				    |
			-------------------------
			|			|
		ou=locations		ou=local-data
		   |
		   + ou=europe
			| is
referral to ldap://ldap-4.foo.com/ou=europe,ou=locations,dc=foo,dc=com


Replication Scenario:

Top Level (dc=foo,dc=com)
---------------------------------------
Master:		ldap-1
Replicas:	ldap-2, ldap-3


Second Level (ou=europe,dc=foo,dc=com)
---------------------------------------
Master:		ldap-4
Replicas:	ldap-5, ldap-6


 So, you can see that a virtual tree is formed via the use of referrals.
Everything is fine if "ldap-1" dies, since the same referral has been
replicated to "ldap-2" and "ldap-3" and clients can query those boxes.

 What happens if "ldap-4" dies? There are two replicas of "ldap-4" waiting
to service requests, but the referral from the top-level doesn't point to
them. The virtual tree becomes broken and requires manual intervention to
"fix" it, e.g.  modifying the referral on "ldap-1" to point to "ldap-5"
or to "ldap-6".

 Does somebody know of a more intelligent and automatic method of
handling this? Replies to list and my email, please :-)

Thanks,
Mike