Re: Question about contextCSN's

[Howard Chu <hyc@symas.com>]

Ryan Steele wrote:
> Ryan Steele wrote:
>> I'm not quite sure how to interpret that though, given the results I'm seeing in my master-master pair.  Should the
>> contextCSN's in the backend database for both SID 001 and SID 002 match?  E.g.:
>>
>> contextCSN: 20100126210305.876171Z#000000#001#000000
>> contextCSN: 20100126210305.876171Z#000000#002#000000
>>
>> Or should both nodes agree about the timestamps for each SID independently?  E.g.:
>>
>> ### ldap1
>> contextCSN: 20100126210305.876171Z#000000#001#000000
>> contextCSN: 20091018205321.288716Z#000000#002#000000
>>
>> ### ldap2
>> contextCSN: 20100126210305.876171Z#000000#001#000000
>> contextCSN: 20091018205321.288716Z#000000#002#000000
>>
> 
> Ah, I think I understand, and if my understanding is correct, the second case is the true statement.  That is, the
> backend database on each node should agree about the most recent timestamp made by SID 001, indicating that they all
> received the same (most current) write from SID 001.  I guess the question that remains in my mind, then, is why keep
> more than one contextCSN per database?  Aren't we only concerned with the last write made to it (in this case, SID 001's
> write)?  Thanks again for the insight.

That's only true in single-master replication. (Which is why the sid field was
always unused up till mirrormode was introduced in 2.4.)

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