(ITS#3711) [enhancement] back-meta and overlapping targets

[ando@sys-net.it]

Full_Name: Pierangelo Masarati
Version: HEAD
OS: irrelevant
URL: ftp://ftp.openldap.org/incoming/
Submission from: (NULL) (81.72.89.40)
Submitted by: ando


Back-meta allows to glue together remote hosts that serve overlapping naming
contexts; for instance, one may glue two servers that both serve
"dc=example,dc=com".  Note that in this case, a violation of the LDAP data model
occurs because two different bits of information cannot have the same DN and be
part of the same distributed DSA.  However, there might be need for this feature
whenever the administrator of back-meta can ensure, by different means, that the
data model is otherwise preserved.

Again an example: suppose target 0 serves "dc=example,dc=com" and only provides
the context entry and the "ou=People" tree, while target 1 serves
"dc=example,dc=com" and only provides the context entry and some trees including
"ou=Groups", "ou=Admin" and so.  The back-meta administrator may want to glue
the context entry from target 0 and the forest of target 1, excluding the
context entry from the latter.

Currently, this cannot be done; but there would be a simple way to do it by
providing each target a scope modifier in addition to the currently provided
base modifier.

For instance:

database        meta
suffix          dc=example,dc=com
uri             ldap://target0/dc=example,dc=com
uri             ldap://target1/dc=example,dc=com

would return two instances of the "dc=example,dc=com" entry; the suggested
enhancement would allow

database        meta
suffix          dc=example,dc=com
uri             ldap://target0/dc=example,dc=com
uri             ldap://target1/dc=example,dc=com??subordinate

so target 1 would be serving namingContext "dc=example,dc=com" but only for
requests __below__ it.

The use of the URI directive to specify targets also suggests more enhancements
(that are out of scope for this ITS); e.g. the possibility to limit the
attributes back-meta will be accessing, or the possibility to specify additional
filters and so.

p.