RE: Need new replica configuration without shutting down slapd

["Howard Chu" <hyc@highlandsun.com>]

> -----Original Message-----
> From: owner-openldap-devel@OpenLDAP.org
> [mailto:owner-openldap-devel@OpenLDAP.org]On Behalf Of Ganesan R

> Hi,
>
> I have a need for adding/removing OpenLDAP replicas in a
> multi-master setup
> with two requirments

> 1. Minimizing (or totally avoiding) config file changes.
> 2. Automatic new replica creation especially without restarting any slapd
>    instance.
>
> To accompish 1, I am working on a design which will put replica
> information
> inside the database. This way replica information propagates to
> all servers
> by normal replication instead of by modifying individual conf files. I am
> making reasonable progress with this.

Sounds interesting. Kind of like my slapd.conf backend. I haven't come up
with sensible semantics for all the possible operations on it, perhaps I
set my initial sights too high...

> I now need a way of achieving 2. My idea is to bring up the new replica
> server with a minimal database and have an application on the other side
> (probably by a modified slurpd) to read the database (similar to
> slapcat) and
> bring the replica uptodate.
>
> Is it okay for a tool to read the database in read only mode while the
> slapd is still running? Will there be a need to flush the
> database cache in
> slapd or is it okay to configure slapd to flush after every update?

The default behavior for back-ldbm is to flush after every update, unless
you use the "dbnosync" keyword in the configuration. However, depending on
what DBM library you use, it may not be possible to access the database
while slapd is running. For example, if back-ldbm is using gdbm, the
database will be opened with a write-lock. If you use gdbm in another
application, it should be unable to obtain a read-lock on the database. In
general, with back-ldbm, only the slapd process should have access to the
database.

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