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href="https://fedorahosted.org/389/ticket/47368">https://fedorahosted.org/389/ticket/47368</a>
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So we run into issues when trying to figure out if replicas are in
synch(if those replicas use fractional replication and "strip
mods"). What happens is that an update is made on master A, but
due to fractional replication there is no update made to any
replicas. So if you look at the ruv in the tombstone entry on each
server, it would appear they are out of synch. So using the ruv
in the db tombstone is no longer accurate when using fractional
replication.
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I'm proposing a new ruv to be stored in the backend replica entry:
e.g. cn=replica,cn="dc=example,dc=com",cn=mapping tree,cn=config.
I'm calling this the "replicated ruv". So whenever we actually
send an update to a replica, this ruv will get updated. Since we
can not compare this "replicated ruv" to the replicas tombstone
ruv, we can instead compare the "replicated ruv" to the ruv in the
replica's repl agreement(unless it is a dedicated consumer - here
we might be able to still look at the db tombstone ruv to
determine the status).
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Problems with this approach:
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- All the servers need to have the same replication
configuration(the same fractional replication policy and attribute
stripping) to give accurate results.
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- If one replica has an agreement that does NOT filter the
updates, but has agreements that do filter updates, then we can
not correctly determine its synchronization state with the
fractional replicas.
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- Performance hit from updating another ruv(in cn=config)?
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Fractional replication simply breaks our monitoring process. I'm
not sure, not without updating the repl protocol, that we can
cover all deployment scenarios(mixed fractional repl agmts, etc).
However, I "think" this approach would work for most
deployments(compared to none at the moment). For IPA, since they
don't use consumers, this approach would work for them. And
finally, all of this would have to be handled by a updated version
of repl-monitor.pl.
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This is just my preliminary idea on how to handle this. Feedback
is welcome!!
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Thanks in advance,
<br>
Mark
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<pre class="moz-signature" cols="72">--
Mark Reynolds
389 Development Team
Red Hat, Inc
<a class="moz-txt-link-abbreviated" href="mailto:mreynolds@redhat.com">mreynolds@redhat.com</a></pre>
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