Re: New Proxy cache overlay

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

Howard Chu wrote:

> > -----Original Message-----
> > From: owner-openldap-devel@OpenLDAP.org
> > [mailto:owner-openldap-devel@OpenLDAP.org]On Behalf Of Pierangelo Masarati
> >    
>
>  
>
> > my DN rewrite/ attr mapping overlay is finally working.
> > I could commit it very quickly (although not finished yet),
> > but there are a couple of side effects:
> >    
>
> I've been thinking that it might make sense to have a rewrite backend. An
> overlay will modify an existing backend's behavior, so that the original
> behavior isn't available. This is probably OK for back-ldap/back-meta that
> are intended to integrate a foreign DIT into a local one. But there's also a
> desire to provide alternate views into a local DIT, and this is where a
> rewrite backend is more useful:
>
> database bdb
> suffix dc=example,dc=com
>
> database rewrite
> suffix o=example.com,c=us
> target dc=example,dc=com
> <various mapping stuff>
>
> The idea here is that the rewrite backend will accept queries for its own
> suffix, and map them to some other backend. This would be the equivalent of
> the old suffixalias functionality, plus the rest of the mapping capabilities.
> The original tree with its unmapped attributes is still directly accessible.
> We can do this right now using back-ldap, but a rewrite backend could just
> call the target backend internally.

Sounds good.

In my view this could be a sort of "transparent" backend,
which relays another backend internally, and the rewrite/map
layer is provided by the overlay.

# trivial case (nonsense: never invoked)
database bdb
suffix dc=example,dc=com

database relay
suffix dc=example,dc=com
target dc=example,dc=com

# rewrite case
database bdb
suffix dc=example,dc=com

database relay
suffix o=example.com,c=us
overlay rewrite-remap
suffixmassage o=example.com,c=us dc=example,dc=com

Relaying would be nearly costless.

This allows to have the rewrite stuff finally in just one place,
and add it also to other backends.  I'm mainly concerned with
back-ldap and scripting backends.

In this sense, it could be useful to separate DN rewriting from
attribute mapping, at the cost of requiring two overlays.

Ando.

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