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Re: slapd-relay and multiple databases

Andrew Reilly wrote:

We have multiple sites that each act as masters to their own db and
replicate back to a pair of central slaves via slurpd.  Views across
the entire organisation are provide by slapd-meta.   Eg:

suffix          "dc=example,dc=com"
uri          "ldap:///dc=site1,dc=example,dc=com";
uri          "ldap:///dc=site2,dc=example,dc=com";


Recently I've begun testing 2.3 and slapd-relay.  The direct access to
the db looks like it might provide a performance boost.

That's what it was intended for :)

However, I
can't seem to find any documentation on having one virtual context
refer to multiple backend databases. Is this possible?


Because back-relay natively doesn't provide any such capability, except ...

- you can omit any "relay" directive; in that case, the relay database relays any database that matches the rewritten request DN; then you move mapping to multiple targets to the rewrite rules. Of course, the rewritten request DN will result in selecting a single database, so this does not constitute a complete replacement of back-meta.

- or, you should be able to have essentially the same functionalities by glueing together different databases, and having back-relay refer to the glued database. I note that since DN rewriting is done with slapo-rwm, this may result in some interoperability issues with slapo-glue. The only reliable way of having slapo-glue and slapo-rwm interact was by instantiating slapo-rwm as a global overlay, so that all requests pass thru it before eventually getting to slapo-glue. See test039 for a clear example.

I've also seen talk on the list that slapd-meta might be going away. What would be the recommended way for me to accomplish what I'm doing
if back-relay does not support multiple databases?


That will eventually happen, but not soon, since no complete replacement is foreseen right now. There are few funcionalities, e.g. concurrent target access and overlapping naming contexts that cannot be emulated by any combination of other existing features. So you can count on having back-meta fully supported and enhanced for quite a while (as soon as we get sponsorship to support it, at least...).

p.


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