Re: [ldapext] nfsv4 vs the ldap consistency model

[Kurt Zeilenga <Kurt.Zeilenga@isode.com>]

On Nov 23, 2008, at 7:12 AM, Leif Johansson wrote:

> > At present, I'm kind of at b).
> >
> > But I don't see how that changes the replication consistency.  In
> > particular, replication of the data for which the condition depends
> > upon would still only eventually consistent.
>
> It requires that the server does the work of waiting for the update
> operation to finish on all slaves. If the update failed on one of the
> slaves the operation would return an error immediately.

This implies not only transactional consistency (all shadow replicas  
are updated at once), but a distributed transaction (all master and  
shadow replicas updated as at once).

I would suggest if that is what the client is expecting that it always  
specify the dontUseCopy control on read operations.  dontUseCopy  
requires the operation be against an authoritative copy.  While  
generally, that's THE master copy, it would extend to all copies  
updated transactionally by the request.

> > If what they are after is transactional consistency, there may be
> > existing LDAP implementations which provide this.  I recall something
> > be presented in this area at LDAPcon.
>
> Transactional consistency would solve the problem but I think what
> they need is somewhat less than transactional consistency. Not sure
> if it is less enough to warrant a standard extension.

dontUseCopy is not yet a standard extension (in LDAP).

> 	Cheers Leif
>
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