[Date Prev][Date Next] [Chronological] [Thread] [Top]

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

çæ(Seuler.shi) wrote:
I just solve the problem and the BDB replication can work well with the OpenLDAP.
The back-bdb caching mechanism is not removed. I will test the performance while
deploying back-bdb configuration in OpenLDAP.

Have fun testing. You're getting well ahead of yourself; first you have to demonstrate that your code is correct, before testing its performance. Some of the most common replication scenarios for OpenLDAP will immediately fail with BDB replication, simply because BDB assumes identical configurations on all servers. As such, any performance measurements you make are purely academic.

If you're looking for a good learning exercise, why not write some code that will actually be useful...

----Seuler

2006/12/14, Howard Chu <hyc@symas.com <mailto:hyc@symas.com>>:

    This is a pointless exercise.

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