backend requirements for syncrepl

[Pierangelo Masarati <ando@sys-net.it>]

It appears to me (please correct me if didn't get it right) that 
currently, to be able to support syncrepl, a backend needs to honor the 
entryUUID and entryCSN operational attributes.  Both of them can be 
generated by slapd (via the appropriate lutil functions).  The latter, 
entryCSN, for syncrepl to work correctly can even be generated on the 
fly, resulting, at worst, in unnecessary overhead in the consumer 
because entries that are already up to date would appear out of sync. 
On the contrary, the former, entryUUID, must be preserved across 
synchronization sessions.  For those backends that do not allow to store 
this information, entryUUID is likely to be an issue.  I'm thinking 
about back-sql, of course, but the same considerations may apply to 
other backend types, like back-perl, back-shell and so, if syncrepl is 
to be used without being intrusive into the actual storage (if any!). 
For this purpose, I'm considering the possibility to implement an 
in-memory, or even on-disk cache that maps DN to entryUUID (although 
defeating the purpose of UUIDs, in some sense!).  Comments?  Am I 
overlooking anything?  Is there a possibility that any of the above is 
not, or may not be in a near future, strictly required by syncrepl?

p.



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