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From "Howard Chu (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DIRSERVER-1651) rfc 4533 implementation differences between openldap and apacheDS
Date Wed, 31 Aug 2011 20:08:12 GMT

    [ https://issues.apache.org/jira/browse/DIRSERVER-1651?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13094858#comment-13094858
] 

Howard Chu commented on DIRSERVER-1651:
---------------------------------------


That's probably the easiest thing to do. Sorry for this; OpenLDAP clearly 
deviated from the intention of RFC4533 here. I.e., the cookie was meant to be 
an opaque value that is not interpreted by the consumers. I believe in the 
usual case, a consumer that needed to "know" the replication state was 
supposed to generate its own private state, independent of the cookie that the 
provider sent.

Unfortunately this intention simply doesn't work in the real world. The view 
of entities as being only providers or only consumers is too simplistic. Even 
when syncrepl was first being developed, we had the notion of cascaded 
replication, where a consumer was itself a provider to other downstream 
consumers. When you have multiple entities participating in replication, it's 
important to be able to see that each one's notion of the replication state 
agrees with everyone else's. It's also important to be able to determine this 
without knowing in advance whether an entity is a provider or a consumer. 
Particularly since in cascading or multi-master replication, the entity is both.

So in OpenLDAP we abandoned the notion that consumers could just stash the 
provider's cookie without peeking inside, and could generate their own cookies 
independently if they were going to serve as providers to other servers.

I believe we could have made it work correctly, with each server generating 
its own state and leaving received cookies as opaque values, but then it would 
have been impossible to do a simple query to see if two entities are in sync.


-- 
   -- Howard Chu
   CTO, Symas Corp.           http://www.symas.com
   Director, Highland Sun     http://highlandsun.com/hyc/
   Chief Architect, OpenLDAP  http://www.openldap.org/project/


> rfc 4533 implementation differences between openldap and apacheDS
> -----------------------------------------------------------------
>
>                 Key: DIRSERVER-1651
>                 URL: https://issues.apache.org/jira/browse/DIRSERVER-1651
>             Project: Directory ApacheDS
>          Issue Type: Bug
>          Components: ldap
>    Affects Versions: 2.0.0-M2
>            Reporter: Hajo Kliemeck
>              Labels: 4533, openldap, syncrepl
>
> Tthere is an incompatibility between the RFC 4533 implementation of apacheDS and openldap.
> openldap uses the cookie structure "rid=<replicaId>" (initial) or "rid=<replicaId>,csn=<Csn
value>" (update) while apacheDS is using NULL for the initial state and the structure "<replicaId>;<Csn
value>" for the update state. in the RFC its said:
> {quote}
> The absence of a cookie or an initialized synchronization state in a cookie indicates
a request for initial content.....
> {quote}
> first is apacheDS like, second is openldap like
> It should be possible to adapt the structure or the behavior.

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