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<div class="moz-cite-prefix">On 06/24/2015 11:36 AM, Oleg Fayans
wrote:<br>
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<div class="moz-cite-prefix">On 06/24/2015 11:25 AM, Ludwig
Krispenz wrote:<br>
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Oleg,<br>
<br>
the topology plugin relies on existing connection between
servers which remain in a topolgy. If you remove a central node
in your topology you are asking for trouble.<br>
With Petr's patch it warns you that your topology will be
disconnected, and if you insist we cannot guarantee anything.<br>
</blockquote>
Agree. I just wanted to try edge cases to see how one can break
the system :)
<blockquote cite="mid:558A7798.8020000@redhat.com" type="cite">
should we completely prohibit this ? I don't know, I think you
could also enforce an uninstall of vm175 with probably the same
result.<br>
what you mean be calculating the remaining topology and send it
to the remaining servers does not work, it would require to send
a removal of a segment, which would be rejected.<br>
<br>
The topology is broken, and I don't know how much we should
invest in making this info consistent on all servers. <br>
<br>
More interesting would be if we can heal this later by adding
new segments.<br>
</blockquote>
Yes, here comes the biggest question raised from this case:
obviously, when none of the nodes possess the correct topology
information (including the one which deleted the central node),
there is no way to fix it by adding segments connecting the nodes
that became disconnected. </blockquote>
It shoul not need the full information, but it has to be able to
reach one of the nodes to be connected. when the topology is broken,
you loose to feature to be ably to apply a change on any node, eg in
your case if you want to connect vm036 and vm056 an have removed
vm175, you have to do it on vm056, vm036 or vm244. This should work,
if not we have to fix it - unless we completely prevent
disconnecting a topology<br>
<blockquote cite="mid:558A7A09.9060408@redhat.com" type="cite">I
still think that the recalculation of the resulting tree should be
done at least on the node that performs the removal action. And
when later some other node gets connected, it should understand
somehow that it's topology information is outdated<br>
<blockquote cite="mid:558A7798.8020000@redhat.com" type="cite"> <br>
Ludwig<br>
<div class="moz-cite-prefix">On 06/24/2015 11:04 AM, Oleg Fayans
wrote:<br>
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<blockquote cite="mid:558A729F.1030307@redhat.com" type="cite">
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Hi everybody,<br>
<br>
Current implementation of topology plugin (including patch 878
from Petr) allows the deletion of the central node in the star
topology.<br>
I had the following topology:<br>
<br>
vm056 vm036<br>
\ / |<br>
vm175 |<br>
/ \ |<br>
vm127 vm244<br>
<br>
I was able to remove node vm175 from node vm244:<br>
<br>
[17:54:48]ofayans@vm-244:~]$ ipa-replica-manage del
vm-175.idm.lab.eng.brq.redhat.com <br>
Topology after removal of vm-175.idm.lab.eng.brq.redhat.com
will be disconnected:<br>
Server vm-036.idm.lab.eng.brq.redhat.com can't contact
servers: vm-056.idm.lab.eng.brq.redhat.com,
vm-127.idm.lab.eng.brq.redhat.com<br>
Server vm-056.idm.lab.eng.brq.redhat.com can't contact
servers: vm-244.idm.lab.eng.brq.redhat.com,
vm-036.idm.lab.eng.brq.redhat.com,
vm-127.idm.lab.eng.brq.redhat.com<br>
Server vm-127.idm.lab.eng.brq.redhat.com can't contact
servers: vm-244.idm.lab.eng.brq.redhat.com,
vm-056.idm.lab.eng.brq.redhat.com,
vm-036.idm.lab.eng.brq.redhat.com<br>
Server vm-244.idm.lab.eng.brq.redhat.com can't contact
servers: vm-056.idm.lab.eng.brq.redhat.com,
vm-127.idm.lab.eng.brq.redhat.com<br>
Continue to delete? [no]: yes<br>
Waiting for removal of replication agreements<br>
unexpected error: limits exceeded for this query<br>
<br>
I would expect this operation to delete 4 replication
agreements on all nodes:<br>
vm056 - vm175<br>
vm127 - vm175<br>
vm244 - vm175<br>
vm036 - vm175<br>
<br>
However an arbitrary set of replication agreements was deleted
on each node leading to total infrastructure inconsistency:<br>
===============================================================<br>
vm056<b> </b>thought the topology was as follows:<br>
vm056 vm036<br>
/ |<br>
vm175 |<br>
/ \ |<br>
vm127 vm244<br>
[10:28:55]ofayans@vm-056:~]$ ipa topologysegment-find realm<br>
------------------<br>
4 segments matched<br>
------------------<br>
Segment name: 036-to-244<br>
Left node: vm-036.idm.lab.eng.brq.redhat.com<br>
Right node: vm-244.idm.lab.eng.brq.redhat.com<br>
Connectivity: both<br>
<br>
Segment name:
vm-036.idm.lab.eng.brq.redhat.com-to-vm-175.idm.lab.eng.brq.redhat.com<br>
Left node: vm-036.idm.lab.eng.brq.redhat.com<br>
Right node: vm-175.idm.lab.eng.brq.redhat.com<br>
Connectivity: both<br>
<br>
Segment name:
vm-127.idm.lab.eng.brq.redhat.com-to-vm-175.idm.lab.eng.brq.redhat.com<br>
Left node: vm-127.idm.lab.eng.brq.redhat.com<br>
Right node: vm-175.idm.lab.eng.brq.redhat.com<br>
Connectivity: both<br>
<br>
Segment name:
vm-175.idm.lab.eng.brq.redhat.com-to-vm-244.idm.lab.eng.brq.redhat.com<br>
Left node: vm-175.idm.lab.eng.brq.redhat.com<br>
Right node: vm-244.idm.lab.eng.brq.redhat.com<br>
Connectivity: both<br>
----------------------------<br>
Number of entries returned 4<br>
----------------------------<br>
===============================================================<br>
both vm036<b> </b>vm244 thought the topology was as follows:<br>
vm056 vm036<br>
\ |<br>
vm175 |<br>
/ |<br>
vm127 vm244<br>
<br>
[10:26:23]ofayans@vm-036:~]$ ipa topologysegment-find<br>
Suffix name: realm<br>
------------------<br>
3 segments matched<br>
------------------<br>
Segment name: 036-to-244<br>
Left node: vm-036.idm.lab.eng.brq.redhat.com<br>
Right node: vm-244.idm.lab.eng.brq.redhat.com<br>
Connectivity: both<br>
<br>
Segment name:
vm-056.idm.lab.eng.brq.redhat.com-to-vm-175.idm.lab.eng.brq.redhat.com<br>
Left node: vm-056.idm.lab.eng.brq.redhat.com<br>
Right node: vm-175.idm.lab.eng.brq.redhat.com<br>
Connectivity: both<br>
<br>
Segment name:
vm-127.idm.lab.eng.brq.redhat.com-to-vm-175.idm.lab.eng.brq.redhat.com<br>
Left node: vm-127.idm.lab.eng.brq.redhat.com<br>
Right node: vm-175.idm.lab.eng.brq.redhat.com<br>
Connectivity: both<br>
----------------------------<br>
Number of entries returned 3<br>
----------------------------<br>
<br>
===============================================================<br>
<b> </b>vm127 thought the topology was as follows:<br>
vm056 vm036<br>
\ / |<br>
vm175 |<br>
\ |<br>
vm127 vm244<br>
<br>
[10:31:08]ofayans@vm-127:~]$ ipa topologysegment-find realm<br>
------------------<br>
4 segments matched<br>
------------------<br>
Segment name: 036-to-244<br>
Left node: vm-036.idm.lab.eng.brq.redhat.com<br>
Right node: vm-244.idm.lab.eng.brq.redhat.com<br>
Connectivity: both<br>
<br>
Segment name:
vm-036.idm.lab.eng.brq.redhat.com-to-vm-175.idm.lab.eng.brq.redhat.com<br>
Left node: vm-036.idm.lab.eng.brq.redhat.com<br>
Right node: vm-175.idm.lab.eng.brq.redhat.com<br>
Connectivity: both<br>
<br>
Segment name:
vm-056.idm.lab.eng.brq.redhat.com-to-vm-175.idm.lab.eng.brq.redhat.com<br>
Left node: vm-056.idm.lab.eng.brq.redhat.com<br>
Right node: vm-175.idm.lab.eng.brq.redhat.com<br>
Connectivity: both<br>
<br>
Segment name:
vm-175.idm.lab.eng.brq.redhat.com-to-vm-244.idm.lab.eng.brq.redhat.com<br>
Left node: vm-175.idm.lab.eng.brq.redhat.com<br>
Right node: vm-244.idm.lab.eng.brq.redhat.com<br>
Connectivity: both<br>
----------------------------<br>
Number of entries returned 4<br>
----------------------------<br>
<br>
If I, for example, add a segment connecting vm127 and vm244,
these two nodes will not synchronize the topology info:<br>
<br>
[10:51:03]ofayans@vm-127:~]$ ipa topologysegment-add realm
127-to-244 --leftnode=vm-127.idm.lab.eng.brq.redhat.com
--rightnode=vm-244.idm.lab.eng.brq.redhat.com --direction=both<br>
--------------------------<br>
Added segment "127-to-244"<br>
--------------------------<br>
Segment name: 127-to-244<br>
Left node: vm-127.idm.lab.eng.brq.redhat.com<br>
Right node: vm-244.idm.lab.eng.brq.redhat.com<br>
Connectivity: both<br>
[10:53:33]ofayans@vm-127:~]$ ipa topologysegment-find realm<br>
------------------<br>
5 segments matched<br>
------------------<br>
Segment name: 036-to-244<br>
Left node: vm-036.idm.lab.eng.brq.redhat.com<br>
Right node: vm-244.idm.lab.eng.brq.redhat.com<br>
Connectivity: both<br>
<br>
Segment name: 127-to-244<br>
Left node: vm-127.idm.lab.eng.brq.redhat.com<br>
Right node: vm-244.idm.lab.eng.brq.redhat.com<br>
Connectivity: both<br>
<br>
Segment name:
vm-036.idm.lab.eng.brq.redhat.com-to-vm-175.idm.lab.eng.brq.redhat.com<br>
Left node: vm-036.idm.lab.eng.brq.redhat.com<br>
Right node: vm-175.idm.lab.eng.brq.redhat.com<br>
Connectivity: both<br>
<br>
Segment name:
vm-056.idm.lab.eng.brq.redhat.com-to-vm-175.idm.lab.eng.brq.redhat.com<br>
Left node: vm-056.idm.lab.eng.brq.redhat.com<br>
Right node: vm-175.idm.lab.eng.brq.redhat.com<br>
Connectivity: both<br>
<br>
Segment name:
vm-175.idm.lab.eng.brq.redhat.com-to-vm-244.idm.lab.eng.brq.redhat.com<br>
Left node: vm-175.idm.lab.eng.brq.redhat.com<br>
Right node: vm-244.idm.lab.eng.brq.redhat.com<br>
Connectivity: both<br>
----------------------------<br>
Number of entries returned 5<br>
----------------------------<br>
[10:54:02]ofayans@vm-127:~]$ <br>
<br>
=============================================================<br>
<br>
[10:49:38]ofayans@vm-244:~]$ ipa topologysegment-find realm<br>
------------------<br>
3 segments matched<br>
------------------<br>
Segment name: 036-to-244<br>
Left node: vm-036.idm.lab.eng.brq.redhat.com<br>
Right node: vm-244.idm.lab.eng.brq.redhat.com<br>
Connectivity: both<br>
<br>
Segment name: 127-to-244<br>
Left node: vm-127.idm.lab.eng.brq.redhat.com<br>
Right node: vm-244.idm.lab.eng.brq.redhat.com<br>
Connectivity: both<br>
<br>
Segment name:
vm-056.idm.lab.eng.brq.redhat.com-to-vm-175.idm.lab.eng.brq.redhat.com<br>
Left node: vm-056.idm.lab.eng.brq.redhat.com<br>
Right node: vm-175.idm.lab.eng.brq.redhat.com<br>
Connectivity: both<br>
----------------------------<br>
Number of entries returned 3<br>
----------------------------<br>
[10:56:34]ofayans@vm-244:~]$ <br>
<br>
<big>Conclusion:</big><br>
We either should completely prohibit the removal of the middle
nodes (I mean, nodes that hide another active nodes),<br>
or at the removal stage first recalculate the resulting
topology and send it to all nodes before actual removal.<br>
<pre class="moz-signature" cols="72">--
Oleg Fayans
Quality Engineer
FreeIPA team
RedHat.</pre>
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<pre class="moz-signature" cols="72">--
Oleg Fayans
Quality Engineer
FreeIPA team
RedHat.</pre>
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