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Re: (ITS#4778) Problem using Berkeley DB replication in OpenLDAP

This is a pointless exercise.

--On Thursday, December 14, 2006 2:27 PM +0800 "çæ(Seuler.shi)" <seuler.shi@gmail.com> wrote: 

Dear Quanah:

            Because the replication features provided by OpenLDAP do not
meet our software requirement.
            If there are N slaves and 1 master in a replication group in
BDB, once the master crashes, a new
            master will be elected by BDB and the replication group can
still work well. All the parameters
            concerning master election in BDB can be configured by user.
This will be more portable.


OpenLDAP mirrormode allows automatic promotion of a slave to a master.

Using LDAP for the control protocol is far more portable. It provides an open, standard protocol for managing all of the servers. Using back-config on each server will allow you to tune all of the server parameters, including the underlying BDB parameters, from anywhere on the network, using any of a variety of LDAP-enabled clients.

Using LDAP for the replication protocol is far more portable. It allows data to be replicated to any LDAP-aware server, not just other OpenLDAP servers.

Relying solely on BDB replication does not provide such power or flexibility.

            As the replication mechanism reaches synchronizations by
transferring write requests to the replicas,
            this may be less efficient compared with BDB replication. So
we need to compare these two method.

Transmitting a single LDAP write operation over the network is far more bandwidth-efficient than transmitting the many database pages that will be dirtied by a single LDAP write operation.

            Would you tell me why OpenLDAP do not support BDB
replication?


Because BDB replication offers no advantages for OpenLDAP's use cases.

            BDB replication mechanism will operate slave databases
directly without inform the upper layer LDAP.
            The information such as index, ID and so on maintained by
OpenLDAP may be inconsistent with the
             content of database. I try to mend the source code of
OpenLDAP to let every "ldapsearch" operation
            find entry info in database directly, but I failed:(

I am expecting your comments.

The only way to make it work is by removing all of the back-bdb caching mechanisms. Performance will be extremely slow. You will lose a significant degree of usability and gain no benefit in return for this effort.

--
  -- Howard Chu
  Chief Architect, Symas Corp.  http://www.symas.com
  Director, Highland Sun        http://highlandsun.com/hyc
  OpenLDAP Core Team            http://www.openldap.org/project/