Re: (ITS#4239) Maintain Replica CSN information without syncrepl in place

[quanah@stanford.edu]

--On Thursday, December 01, 2005 8:17 PM +0000 hyc@symas.com wrote:

> quanah@stanford.edu wrote:
>> Full_Name: Quanah Gibson-Mount
>> Version: 2.3.13
>> OS: Solaris 8
>> URL: ftp://ftp.openldap.org/incoming/
>> Submission from: (NULL) (171.66.155.86)
>>
>>
>> This is kind of a feature enhancement request.
>>
>> Essentially, I've looked at moving from slurpd-> delta-syncrepl a few
>> times now. However, various problems have kept me from doing this
>>  permanently, and I've had to move back to slurpd.  Every time I then
>> want to try delta-syncrepl again, I have to reload the replicas to have
>> their CSN's be in sync with what the master has.
>>
>
> slurpd replicates all the operational attributes, including entryCSN. As
> such, reloading the database isn't necessary.


However, the contextCSN in the slaves naming context doesn't match the 
master's contextCSN at all.  If I put accesslog in place for 
delta-syncrepl, I'm concerned that'll trigger a full reload on the 
replicas, which would take many hours longer than just doing a slapadd of 
the DB.

>> It has made me think it would be really handy if there was a way to have
>> the replica keep its contextCSN updated even if someone isn't using
>> syncrepl, to make that conversion easier at a later date.
>>
>
> Just install the syncprov overlay on each replica, and configure the
> syncprov-checkpoint.

Okay, that seems simple enough.

>> In fact, is there any reason not to simply always keep the CSN
>> information up to date?
>>
>
> Yes - all of the syncrepl related reorganization that occurred between
> 2.2 to 2.3 was done to insure that the baseline code doesn't have any
> extraneous features. Since writing the contextCSN further serializes all
> write operations, doing so decreases overall write throughput. The
> contextCSN is only useful for syncrepl; nobody who isn't using it should
> have to pay the performance penalty for it.

Okay, makes sense.

--Quanah


--
Quanah Gibson-Mount
Principal Software Developer
ITSS/Shared Services
Stanford University
GnuPG Public Key: http://www.stanford.edu/~quanah/pgp.html