A general purpose LDAP solution?

[Matthew Seaman]

Patrick C wrote:

> Is there any support for built-in redundancy on the server level? I just
> need changes replicated, CARP can handle failover.

with LDAP? Sure.  In fact, there are two mechanisms available with
OpenLDAP: replicated and 'syncrepl'.  See

http://www.openldap.org/doc/admin24/config.html#Replicated%20Directory%20Service

Actually, that diagram is confusing: the basic replication uses a 
separate process 'slurpd' to manage updating the slave server, whereas
synchronous replication just uses a connection from the slave slapd to
the master. Synchrepl seems to me to be the way to go.

In any case, the way the system works is this: one LDAP instance is the
master and the only one to allow writes to itself.  The other instances
get a feed of all updates which allows them to maintain a duplicate of
the database contents.  You can issue writes to the slave LDAPs but they
will be transformed into referrals to the master server -- ie. your client
needs to be able to access the master if it needs to write to the database.

ie. If all you ever want to do is *read* from LDAP during normal operation,
then you can make a nice replicated resilient system.  If you need to
routinely *write* to the DB, then no, you need to have the master server
available.

	Cheers,

	Matthew

-- 
Dr Matthew J Seaman MA, D.Phil.                   7 Priory Courtyard
                                                  Flat 3
PGP: http://www.infracaninophile.co.uk/pgpkey     Ramsgate
                                                  Kent, CT11 9PW

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