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From Howard Chu <...@symas.com>
Subject Re: [jira] Created: (DIRSERVER-1098) New replicas may never be synchronised
Date Wed, 14 Nov 2007 17:00:10 GMT
Martin Alderson (JIRA) wrote:
> New replicas may never be synchronised
> --------------------------------------
> 
>                  Key: DIRSERVER-1098
>                  URL: https://issues.apache.org/jira/browse/DIRSERVER-1098
>              Project: Directory ApacheDS
>           Issue Type: Bug
>           Components: mitosis
>     Affects Versions: 1.5.1
>             Reporter: Martin Alderson
>             Assignee: Martin Alderson
>             Priority: Minor
> 
> 
> When the currently running replicas no longer have the original
> modification
logs and a new replica is added and then modified before it has been brought
up to date then it will never be brought up to date.
> 
> I am currently testing a fix for this which will disallow all
> modifications
to the new replica until it has been brought up to date.

Is there a doc somewhere that describes the replication protocol?

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...
-- 
   -- 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/

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