Issue 8790 - N-Way MMR w/o serverID in at least one entry causes REFRESH
Summary: N-Way MMR w/o serverID in at least one entry causes REFRESH
Status: VERIFIED FIXED
Alias: None
Product: OpenLDAP
Classification: Unclassified
Component: slapd (show other issues)
Version: 2.4.45
Hardware: All All
: --- normal
Target Milestone: ---
Assignee: OpenLDAP project
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2017-12-12 01:15 UTC by Quanah Gibson-Mount
Modified: 2018-02-07 17:14 UTC (History)
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Description Quanah Gibson-Mount 2017-12-12 01:15:13 UTC 
Full_Name: Quanah Gibson-Mount
Version: 2.4.45
OS: N/A
URL: ftp://ftp.openldap.org/incoming/
Submission from: (NULL) (47.208.148.239)


If one has configured N-WAY MMR in such a fashion that only one master ever gets
the write ops (whether this is mirrormode or other methodologies), and there are
zero entries in the database with an entryCSN of the other masters in the
system, attempts to bring those other masters back up will result in a REFRESH
phase on those masters, and potentially destabilize the entire cluster (See
ITS#8789 for example).

To avoid this, we should document that best practice involves having one object
per master that is only ever modified by that master, so there is always a
minimum of one object in the database with a CSN matching that master.  This
should avoid the REFRESH issue when bringing up a failed master.
Comment 1 OpenLDAP project 2018-02-07 17:14:12 UTC 
Fixed with the fix to ITS#8100.
Comment 2 Quanah Gibson-Mount 2018-02-07 17:14:12 UTC 
changed notes
changed state Open to Closed