On 06/13/2016 05:33 AM, Ludwig Krispenz wrote:
Hi German,
you are right that IPA is on the safe side, they maintain the last
used replicaID and when creating a server instance only a higher
replicaid is used, also when a server is removed, the removal triggers
a cleanallruv, either from the script or by the topology plugin (>4.3).
This is because in IPA all server instance creation and removal is
managed by IPA cammands.
This framework is not there by default for "admion managed" DS
deployments, and that's what William wants to get improved.
William,
I'm not sure that the scenario you describe is really so bad as you
think. If a server is removed and the RID is not cleaned, it's
component remains in the RUV, but this is just an overhead in
examining ruvs, but should not block replication to continue. If a new
server with the old, removed replicaID is installed, the ruv component
should be reused, the URL replaced, and replication continue as if
there haven't been updates for this replica ID for a long time. I'm
saying "should", since there mioght be some cases where the changelog
was purged and an anchor csn for the old/new replicaid cannot be
found. So we need to do some tests and it would be good to make this safe.
One option would be to maintain already used replicaids, so at the
init of a new server there could not only be a check for the same
database generation, but also for a valid RUV
I think it is difficult to find a trigger for an automated
cleanallruv, we would have to maintain something like a topology view
of the deployment, like the topology plugin in IPA does.
William,
"So, an have some idea for this. Any change to a replication agreement,
should trigger a CLEANALLRUV, before we start the
agreement. "
I am assuming you don't mean replication agreement, but instead the
"replica configuration".
One scenario where we could trigger a cleanallruv task is when we demote
a master to a hub/consumer, as well as when we delete a master replica.
This shouldn't be too hard to do, and it makes sense. I'm not sure if
its something that should always be done automatically though(yet
another config option?)
Mark
But it is definitely worth to think about solutions for thi sproblem
Ludwig
On 06/13/2016 10:21 AM, German Parente wrote:
Hi William,
I think this case is covered in IPA. I have never seen a new replica
added with the same former ID of an old one.
The former ruvs are not cleaned automatically, though, in current
versions and it's not a very severe issue now. There are also ipa
commands to list and clean the ruvs.
I have also heard or read that in the dev versions (not still
delivered), the cleaning is automatic, as you are proposing.
Thanks a lot.
regards,
German.
On Mon, Jun 13, 2016 at 7:21 AM, William Brown <wibr...@redhat.com
<mailto:wibr...@redhat.com>> wrote:
Hi,
I was discussing with some staff here in BNE about replication.
It seems a common case is that admins with 2 or 3 servers in MMR
(both DS and IPA) will do this:
* Setup all three masters A, B, C (replica id 1,2,3 respectively)
* Run them for a while in replication
* Remove C from replication
* Delete data, change the system
* Re-add C with the same replica id.
Supposedly this can cause duplicate RUV entries for id 3 in
masters A and B. Of course, this means that replication has all
kinds of insane issues at this point ....
On one hand, this is the admins fault. But on the other, we
should handle this. Consider an admin who re-uses an IPA replica
setup file, without running CLEANALLRUV
So, an have some idea for this. Any change to a replication
agreement, should trigger a CLEANALLRUV, before we start the
agreement. This means on our local master we have removed the bad
RUV first, then we can add the RUV of the newly added master
when needed ....
What do you think? I think that we must handle this better, and
it should be a non-issue to admins.
We can't prevent an admin from intentionally adding duplicate
ID's to the topology though. So making it so that the ID's are not
admin controlled would prevent this, but I haven't any good ideas
about this (yet)
--
Sincerely,
William Brown
Software Engineer
Red Hat, Brisbane
--
389-devel mailing list
389-devel@lists.fedoraproject.org
<mailto:389-devel@lists.fedoraproject.org>
https://lists.fedoraproject.org/admin/lists/389-devel@lists.fedoraproject.org
--
389-devel mailing list
389-devel@lists.fedoraproject.org
https://lists.fedoraproject.org/admin/lists/389-devel@lists.fedoraproject.org
--
Red Hat GmbH,http://www.de.redhat.com/, Registered seat: Grasbrunn,
Commercial register: Amtsgericht Muenchen, HRB 153243,
Managing Directors: Charles Cachera, Michael Cunningham, Michael O'Neill, Eric
Shander
--
389-devel mailing list
389-devel@lists.fedoraproject.org
https://lists.fedoraproject.org/admin/lists/389-devel@lists.fedoraproject.org
--
389-devel mailing list
389-devel@lists.fedoraproject.org
https://lists.fedoraproject.org/admin/lists/389-devel@lists.fedoraproject.org
