Re: Help with modules

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

Howard Chu wrote:

> Herb Hrowal wrote:
>
> > If a shim is possible, can it specify which backend handles the request?
>
> Not quite. Instead, you specify which overlays to use on a particular 
> backend.

Let me elaborate on this: in slapd, requests are processed by the frontend,
which decides, based on the request type and data, which __database__ will
elaborate it (essentially based on finding what database "suffix" is the 
most
appropriate for some DN associated to the request.  In this sense, overlays
intervene __after__ the database (and thus the backend, which is the 
database
type) has been selected.  In HEAD code, however, you can put an overlay
__between__ request parsing and database selection.  As such, by changing
("massaging") the DN associated with the request, you can act on what
database handles it.  OpenLDAP's slapd provides an overlay that deals with
data massaging; see slapo-rwm(5) for details.  You can stack this in the 
frontend
between prequest parsing and database selection, and plug your own overlay
downstream for furthr massaging; or, if you don't need all its 
functionalities,
do your own massaging in your overlay.

p.




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