Re: (ITS#8100) Empty accesslog causes issues with delta-syncrepl MMR configurations

[quanah@symas.com]

--On Friday, January 26, 2018 8:23 PM +0000 hyc@symas.com wrote:

> A patch which skips deleting the final entry, and creates an initial
> dummy log  entry if needed, is available in
> https://github.com/quanah/openldap-scratch/tree/its8100 for testing.

Hi Howard,

When reinstalling a 4-way MMR system from scratch, we still end up in 
REFRESH mode.  In the database I'm loading, there are 4 contextCSN values, 
one per active master:

contextCSN: 20171203010043.825769Z#000000#001#000000
contextCSN: 20171130222521.056018Z#000000#002#000000
contextCSN: 20171130222318.939265Z#000000#003#000000
contextCSN: 20171203041258.811473Z#000000#004#000000

When I start up the first master (serverID 4 in this case), a contextCSN 
value is properly written for it to the underlying db:

Jan 29 10:06:06 anvil4 slapd[1949]: slapd starting
Jan 29 10:06:06 anvil4 slapd[1949]: slap_queue_csn: queueing 0x7f54d4104220 
20171203041258.811473Z#000000#004#000000
Jan 29 10:06:06 anvil4 slapd[1949]: slap_queue_csn: queueing 0x7f54d4104cc0 
20171203041258.811473Z#000000#004#000000
Jan 29 10:06:06 anvil4 slapd[1949]: slap_graduate_commit_csn: removing 
0x7f54d4104cc0 20171203041258.811473Z#000000#004#000000
Jan 29 10:06:06 anvil4 slapd[1949]: slap_graduate_commit_csn: removing 
0x7f54d4104220 20171203041258.811473Z#000000#004#000000


But when I start the other 3 masters, they do not write an entry for their 
CSN, and since there's no CSN value for them on the other masters either, 
they all fall back to REFRESH_DELETE:

Jan 29 10:06:26 anvil4 slapd[1949]: do_syncrep2: rid=003 
LDAP_RES_INTERMEDIATE - REFRESH_DELETE

Even worse, they do this for every master that comes online.

I think the code needs to add an entry to the accesslog for every 
contextCSN value, not just the final contextCSN?

I'll continue testing for the other half of the fix (Deleting all but the 
most recent entry from the accesslog during purge)

Thanks!

--Quanah




--

Quanah Gibson-Mount
Product Architect
Symas Corporation
Packaged, certified, and supported LDAP solutions powered by OpenLDAP:
<http://www.symas.com>