On Thu, Jun 08, 2017 at 06:36:02PM +0100, Ond=C5=99ej Kuzn=C3=ADk wrote:

A more self-contained log of the same issue, available at ftp://ftp.openldap.org/incoming/its8444.log =20 (line numbers below are against current master, commit 91f4d3a6b75e73bf4ea498e83e2e4cb4e7a320e0) =20 There are some things that occur in all the failures I have seen so far=

:

• the server that received the operation (#1) sends the accesslog entry with no CSN in the cookie, then another provider (#2) picks up this message and relays it to its consumers, this one with a CSN in the cookie
• a consumer picks up these two in short succession, in the log above, processing of the one from #2 is finished first (they are being processed concurrently)

=20 Usually, once one of them gets processed, the new CSN should be noted and the other threads should just skip it (syncrepl.c:943 and onwards). In this one, having no CSN in the cookie seems to allow both to process so far as to run syncrepl_message_to_op(), and one of them will then inevitably fail to add the entry. =20 I don't understand yet why server #1 sends the operations without a CSN in the cookie and (especially if I reorder the overlays to set up memberof last), the race goes the other way around and the operation to fail is the one from server #2. =20 My take on it was that in a delta-sync environment all entries would be passed with a new CSN and that should end up in the cookie, allowing syncrepl.c:986 to do its job.

Using the behaviour above, I have been able to trigger a desync, the script and testrun directory from it happening are available here: ftp://ftp.openldap.org/incoming/its8444-desync.tgz

In srv3, looking at cn=3Daccesslog, we can see that the increment by 2 ha= s been applied (and logged) twice with the same entryCSN, as: reqStart=3D20170718155142.000007Z,cn=3Daccesslog reqStart=3D20170718155142.000009Z,cn=3Daccesslog

also seen in the log around those two DNs above.

--=20 Ond=C5=99ej Kuzn=C3=ADk Senior Software Engineer Symas Corporation http://www.symas.com Packaged, certified, and supported LDAP solutions powered by OpenLDAP