Failover and replication with Apache Directory Server 1.5.3

[Chico Charlesworth <CC...@ie.ibm.com>]

Hi,

Can anyone help me with what's the standard approach in guaranteeing 
failover with Apache Directory Server 1.5.3?

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?

Cheers
Chico

Re: Failover and replication with Apache Directory Server 1.5.3

[Emmanuel Lecharny <el...@gmail.com>]

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 Lécharny
www.iktek.com
directory.apache.org

Re: Failover and replication with Apache Directory Server 1.5.3

[Emmanuel Lecharny <el...@gmail.com>]

Hi,

just to correct my previous mail : I have made a confusion between 
restoring a failing system and failover.

Consider my mail being void. Alex answer is the correct one.

Sorry for the noise.

-- 
--
cordialement, regards,
Emmanuel Lécharny
www.iktek.com
directory.apache.org

Re: Failover and replication with Apache Directory Server 1.5.3

[Alex Karasulu <ak...@apache.org>]

On Wed, Aug 6, 2008 at 9:13 AM, Chico Charlesworth <CC...@ie.ibm.com>wrote:

>
> Hi,
>
> Can anyone help me with what's the standard approach in guaranteeing
> failover with Apache Directory Server 1.5.3?
>

The mitosis replication in ApacheDS is designed for multi-master.  So
there's no need to implement a specific failover solution.  Maybe if you
have a smart load balancer that knows when a server is down it can be
blacklisted until brought back up.


>
> 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?
>

There's little documentation on this but you might find what you're looking
for in the mailing list archives.  The configuration file may also have a
sample configuration.

Alex

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