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From Emmanuel Lecharny <>
Subject Re: Failover and replication with Apache Directory Server 1.5.3
Date Wed, 06 Aug 2008 13:43:19 GMT
Chico Charlesworth wrote:
> Hi,
> Can anyone help me with what's the standard approach in guaranteeing 
> failover with Apache Directory Server 1.5.3?
There is no such thing like a guaranteed failover in 1.5.x. But we are 
working on a changelog system which will be available in 2.0 that should 
allow you to restore a failed database (it's already present, and 
working well, but we don't have tooling around it right now)
> I see that a new Multi-Master Replication feature is on the horizon, will 
> this provide what I need and if so is there any readily available 
> documentation?
It depends. Failover is just more than Multi-Master replication, as you 
have no guarantee that some data have been replicated when a server 
crashes. You also have to know that the server is not transactional, so 
you may lose informations anyway.

The base idea is just to log data on a disk as plain text (a journal) so 
that if you have a crash, you can replay the journal. This is not 
something we are currently working on, but that would be a piece of cake 
to do :
- add a Journal Interceptor,
- be sure that the logger logs modifications in the correct order, 
assuming that you may have many simulatenous requests
- and , last, not least, add the mechanism to regenerate the data using 
this log file, assuming that the log file gets truncated each time you 
backup the backend (the server will have to be down when doing the backup)

There is nothing complex, just need time to do it.

Any volunteer contribution in this area would be very welcome !!!
> Cheers
> Chico

cordialement, regards,
Emmanuel L├ęcharny

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