glue and other overlays

[Pierangelo Masarati <ando@sys-net.it>]

I'm having problems in adding overlays to glued databases in 2.3 
(actually, in HEAD) code.  I want to glue together multiple instances of 
back-ldap that must rewrite the DN of requests.  I can do it this way:

--------
# global
overlay rwm
rwm-suffixmassage dc=example,dc=com

database ldap
suffix ou=Meta,o=Example,c=US

database ldap
suffix o=Example,c=US

overlay glue
glue-sub ou=Meta,o=Example,c=US
--------

which is fine if the two database can share the same rewriting; but in 
few cases specific rewriting might be required, and I'd like to be able 
to do things like

--------
database ldap
suffix ou=Meta,o=Example,c=US
overlay rwm
rwm-suffixmassage ou=Meta,dc=example,dc=com

database ldap
suffix o=Example,c=US
overlay rwm
rwm-suffixmassage dc=example,dc=com

overlay glue
glue-sub ou=Meta,o=Example,c=US
--------

but it doesn't work; I can search for "ou=Meta,dc=example,dc=com", but I 
get noSuchObject for "dc=example,dc=com".  I suspect a misuse, since I 
recall reading that per-database overlays are not honored when the glue 
overlay is used, but I can't find that message.  What I've noticed is 
that if I stack an overlay before the glue overlay it doesn't get called 
because the glue overlay directly calls the underlying database after 
resolving the most appropriate one; so

--------
#subordinate instances...

database ldap
suffix o=Example,c=US
overlay rwm
rwm-suffixmassage dc=example,dc=com

overlay glue
glue-sub ou=Meta,o=Example,c=US
--------

is equivalent to

--------
#subordinate instances...

database ldap
suffix o=Example,c=US
# bypassed
# overlay rwm
# rwm-suffixmassage dc=example,dc=com

overlay glue
glue-sub ou=Meta,o=Example,c=US
--------

I tried to use a trick, i.e. to put the rwm __after__ the glue overlay, 
but this doesn't work because the rewritten DN is used to select the 
subordinate, and thus it fails:

--------
#subordinate instances...

database ldap
suffix o=Example,c=US

overlay glue
glue-sub ou=Meta,o=Example,c=US

overlay rwm
rwm-suffixmassage dc=example,dc=com
--------
In fact, in this case the "glue-sub" instance should rather be "glue-sub 
ou=Meta,dc=example,dc=com", but in this case slapd fails when reading 
the configuration, because the first suberdinate has suffix 
"ou=Meta,o=Example,c=US"; I've worked it around by using both suffixes 
in each database, the one ending with "dc=example,dc=com" being required 
only to correctly parse the "glue-sub" directive.  But there's something 
wrong yet, so that the databases are not correctly glued.

p.

--
Pierangelo Masarati
mailto:pierangelo.masarati@sys-net.it



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