Re: contextCSN with empty suffix

Christian Kratzer wrote:
> Hi,
>
> we have a customer who runs an openldap installation with an empty suffix as in
>
>     suffix ""
>
> which is a potential problem when migrating to syncrepl as they do not have
> an entry to store the contextCSN.

Actually it's no problem at all.

> In our lab using openldap 2.4.19 we succeeded in inserting an entry with
> an empty dn as follows:
>
>     dn:
>     objectClass: organization
>     o: root

syncrepl and back-bdb/hdb would have created this entry automatically anyway, 
if it was needed.

> This entry received the contextCSN entries and everything looks good
> from what I can see:
>
>     dn:
>     objectClass: organization
>     o: root
>     structuralObjectClass: organization
>     entryUUID: 6bd316a2-6f10-102e-904e-c754373eef36
>     creatorsName: cn=Manager
>     createTimestamp: 20091126194832Z
>     entryCSN: 20091126194832.284443Z#000000#000#000000
>     modifiersName: cn=Manager
>     modifyTimestamp: 20091126194832Z
>     contextCSN: 20091126194832.864794Z#000000#000#000000
>
> I have no idea how ugly this hack is and am concerned this might break
> with a future release when either searching for contextCSN below the suffix
> is perhaps supported again or entries with an empty dn break.
>
> I am about to advise the customer to move to a directory with an
> nonempty suffix matching their root entry but would like to hear
> nevertheless what you think of above.

There are some situations where this type of config may run into problems, but 
in most cases it works fine. For the rare problem cases, (e.g., using proxy 
syncrepl) an option has been introduced in 2.4.20 to allow the contextCSN to 
be stored in a dedicated subentry instead of in the suffix entry (See 
ITS#6373). But if you're not using proxy syncrepl, there's nothing to worry about.

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