Re: backend overlays

[Howard Chu <hyc@symas.com>]

Pierangelo Masarati wrote:

> If this is completely off-topic, please disregard.
>  
Let me try again... The proxycache overlay sits on top of (e.g.) 
back-ldap. It also creates an instance of back-bdb for its local 
storage. This instance of back-bdb is totally private to the proxycache 
overlay, it is completely invisible to the rest of slapd so you can't 
configure anything special on top of it. The first question in my mind 
was "would you ever need to put another overlay on top of this private 
back-bdb?"

Obviously one way to do so would be to add config mechanisms to 
proxycache so that its private database can be explicitly configured.

The other thought that occurred to me was to declare overlays in the 
backend-specific config directives. Then whenever a backend of that type 
is used, it has these other overlays already included. The problem of 
course is that if the overlay needs any suffix-dependent configuration, 
there's no way to automate that.

e.g.
backend bdb
overlay syncprov
syncprov-sessionlog 100

database bdb
suffix o=foo
...

database bdb
suffix o=bar
...

So each of the two bdb databases would automatically get the syncprov 
overlay attached with a default sessionlog setting of 100.

And to the original point,

database ldap
overlay proxycache
proxycache bdb 1000 10 20
...

would allow the proxy's local storage to provide data to other consumers...

> p.
>
>  
>
> > Every now and then I look at things like the proxycache overlay with its
> > internal database, and wonder if there would ever be a need to put an
> > overlay on that database. I suppose one way to handle that would be to
> > add explicit proxycache directives for configuring such a feature.
> > Another thought that came to mind was being able to declare overlays
> > inside a "backend" section, such that these overlays would automatically
> > be instantiated whenever a particular type of backend is used. Comments?
> >
> > --
> >  -- Howard Chu
> >  Chief Architect, Symas Corp.       Director, Highland Sun
> >  http://www.symas.com               http://highlandsun.com/hyc
> >  Symas: Premier OpenSource Development and Support
> >
> >
> >    
>
>
>  


--
 -- Howard Chu
 Chief Architect, Symas Corp.       Director, Highland Sun
 http://www.symas.com               http://highlandsun.com/hyc
 Symas: Premier OpenSource Development and Support