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Re: slurpd vs ldapsync
flo@redflo.de wrote:
Hi,
Just yesterday i set up slurpd for replication. The openldap
documentation points one to slurpd at many places. Example:
http://www.openldap.org/doc/admin23/config.html#Replicated%20Directory%20Service
No word of an alternative. Could someone give some hints in that chapter
and problably in the chapter "14. Replication with slurpd"?
"Someone" probably could. Maybe that someone should be you. File an ITS.
The FAQ-O-Matic says that "multimaster replication is harmful". Is this
still true as you say that syncrepl works with that?
At a basic level, multi-master replication introduces a lot of
uncertainty/potential inconsistency into the database. The X.500 service
model makes some consistency guarantees that break in a multi-master
environment, and such inconsistencies can certainly cause problems in
many situations.
On the other hand, even single-master isn't perfectly consistent 100% of
the time, due to the delay time in propagating changes from a master to
all of the slaves. And it's always possible for a rapid sequence of
changes to create the appearance of conflicting data. (E.g., a bunch of
modifies in rapid succession, that toggle a particular attribute between
a few values. The value that a reading client sees is really
unpredictable, it just depends on luck, at what instant its search
request is processed, relative to the modifications.)
The syncrepl protocol only offers loose consistency to begin with - it
only guarantees eventual convergence. But what's important is that the
convergence will actually occur. The multi-master support is the same -
it's possible for conflicting views of the data to appear within small
time intervals, but eventually it will all resolve.
Thanks for the nice piece of software.
--
-- Howard Chu
Chief Architect, Symas Corp. http://www.symas.com
Director, Highland Sun http://highlandsun.com/hyc
Chief Architect, OpenLDAP http://www.openldap.org/project/