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From Emmanuel Lecharny <elecha...@gmail.com>
Subject Re: [jira] Created: (DIRSERVER-1098) New replicas may never be synchronised
Date Wed, 14 Nov 2007 22:36:30 GMT
Howard Chu wrote:
>
> Is there a doc somewhere that describes the replication protocol?
Here you are :
http://cwiki.apache.org/confluence/display/DIRxSRVx11/Mitosis

These pages are really very rough.
>
> We encountered similar issues when developing the multimaster support 
> in OpenLDAP. Our solution was simply to assign unique server IDs to 
> each master, and record the last known modification for each known 
> server ID. This way local modifications don't overwrite the (lack of) 
> state from other servers.
>
> Another issue to consider when bringing up a new replica - you may 
> want to disallow all queries completely, until the replica has fully 
> sync'd up. If you allow searches during this initial phase, a client 
> is likely to get a partial set of results. In some cases, that may be 
> worse than getting no result...
The pb is that if you have a lot of replication, it may not be a viable 
approach. Also if you want to implement the 'paging control', as it's up 
to the client to request the next results, you have no good solutions...

At some point, I think we should consider that a LDAP server is not like 
a RDBMS system with a full transaction system, and you must assume that 
dirty read is a standard mode. That does not mean we shouldn't consider 
blocking incoming requests until a sync-up is done when a server is 
restarted.

This is not a simple problem...


-- 
--
cordialement, regards,
Emmanuel L├ęcharny
www.iktek.com
directory.apache.org



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