Re: PATCH: back-sock

[Brian Candler <B.Candler@pobox.com>]

On Thu, Oct 13, 2005 at 10:44:01AM -0700, Howard Chu wrote:
> To me the notions of "externally scripted module" and "production use" 
> are mutually incompatible. You use a scripting backend to prototype an 
> interaction, and if it needs to perform well in production use you 
> rewrite it in C.

That doesn't apply to the situations that I have found myself in, but of
course different approaches are valid in different situations.

Personally, what I want from LDAP is to provide a unified presentation layer
to custom business logic. The most important things to me are that the
business logic can be changed quickly and easily, and is easily verified to
be correct. Performance is secondary; that is, I'm thinking of tens of
queries per second, not ten thousand.

Given that, I think that having the logic in a higher-level scripting
language, where (for example) I don't have to worry about memory allocation
every time I read or create a string, makes a lot of sense.

> I might as well just write an overlay on top
> of back-null. Indeed, with the overlay mechanism I haven't felt the need
> to use back-perl in a very very long time.

These overlays are written in C, right?

I'm interested in finding out more about this mechanism. Is there any
documentation about what overlays are, how they work, and how to write your
own? How is writing your own overlay different to writing your own backend?

All I can find is one paragraph in slapd.conf(5), and some slapo-* pages.
The administrator's guide doesn't seem to have much to say on the matter.

Cheers,

Brian.