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Re: accesslog contextcsn isn't always updated

On Fri, Aug 25, 2017 at 11:36:56PM -0400, btb wrote:
> hi, i am seeing a symptom where the accesslog contextcsn is not always
> updated when a new entry is added to the accesslog.  i have a test setup
> [config is below], with a content database using the accesslog and syncprov
> overlays, and an accesslog database using the syncprov overlay.  for the
> purposes of testing, i'm not using it as a provider for any consumers.  just
> running by itself, and watching its behavior.
> when a modification is made to an entry in the content db, the contextcsn
> value for the content db is always updated, and a new entry is always added
> to the accesslog db.  but when the accesslog db gets a new entry, the
> accesslog contextcsn does not always update to match the new entry [see
> example below].  ldap_accesslog_noop is just a small shell script which
> updates the info attribute for an entry.
> it's somewhat anecdotal, but there may be a timing factor involved.  if
> there is no activity for a little while [as little as a few minutes,
> sometimes], then a modification performed, that does not update the
> accesslog contextcsn.  but if subsequent modifications are done within a few
> moments, it then eventually updates the accesslog contextcsn correctly,
> typically as of the second modification, but sometimes the third.  if
> modifications then continue, with little delay between them, then the
> contextcsn seems to stay consistently up to date.  if activity then stops,
> and some time passes as before, the symptom reappears.
> this is version 2.4.44 on freebsd 10.3-release, built from ports.
> i'm hoping someone can offer some guidance on how to troubleshoot this
> further, or what i might be doing wrong.  i can provide more config details,
> logs, debugging ,etc., if needed.

sounds like the issue I have been investigating in ITS#8444, especially
the "this seems to happen if we wait 5 minutes" with your checkpoint
being set to 5 minutes.

Ondřej Kuzník
Senior Software Engineer
Symas Corporation                       http://www.symas.com
Packaged, certified, and supported LDAP solutions powered by OpenLDAP