Re: [ClusterLabs] Corosync lost quorum but DLM still gives locks
Replying to myself:
On Wed, 11 Oct 2017, Jean-Marc Saffroy wrote:
> I am caught by surprise with this behaviour of DLM:
> - I have 5 nodes (test VMs)
> - 3 of them have 1 vote for the corosync quorum (they are "voters")
> - 2 of them have 0 vote ("non-voters")
>
> So the corosync quorum is 2.
>
> On the non-voters, I run DLM and an application that runs it. On DLM,
> fencing is disabled.
>
> Now, if I stop corosync on 2 of the voters:
> - as expected, corosync says "Activity blocked"
> - but to my surprise, DLM seems happy to give more locks
>
> Shouldn't DLM block lock requests in this situation?
Apparently DLM does not care about changes in quorum until there are
changes in membership of the process groups it is part of. In my test, the
"voters" do not run DLM, and therefore (I suppose?) DLM does not react to
their absence.
DLM does block lock requests when quorum is lost AND THEN there is a
change in membership for the DLM participants, because quorum is required
for lockspace operations.
Does that make sense?
Cheers,
JM
--
saff...@gmail.com
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[ClusterLabs] Corosync lost quorum but DLM still gives locks
Hi,
I am caught by surprise with this behaviour of DLM:
- I have 5 nodes (test VMs)
- 3 of them have 1 vote for the corosync quorum (they are "voters")
- 2 of them have 0 vote ("non-voters")
So the corosync quorum is 2.
On the non-voters, I run DLM and an application that runs it. On DLM,
fencing is disabled.
Now, if I stop corosync on 2 of the voters:
- as expected, corosync says "Activity blocked"
- but to my surprise, DLM seems happy to give more locks
Shouldn't DLM block lock requests in this situation?
Cheers,
JM
--
[root@vm4 ~]# corosync-quorumtool
Quorum information
--
Date: Wed Oct 11 20:29:52 2017
Quorum provider: corosync_votequorum
Nodes:3
Node ID: 5
Ring ID: 3/24
Quorate: No
Votequorum information
--
Expected votes: 3
Highest expected: 3
Total votes: 1
Quorum: 2 Activity blocked
Flags:
Membership information
--
Nodeid Votes Name
3 1 172.16.2.33
4 0 172.16.3.33
5 0 172.16.4.33 (local)
[root@vm4 ~]# dlm_tool status
cluster nodeid 5 quorate 0 ring seq 24 24
daemon now 6908 fence_pid 0
node 4 M add 4912 rem 0 fail 0 fence 0 at 0 0
node 5 M add 4912 rem 0 fail 0 fence 0 at 0 0
[root@vm4 ~]# corosync-cpgtool
Group Name PID Node ID
dlm:ls:XYZ\x00
971 4 (172.16.3.33)
10095 5 (172.16.4.33)
dlm:controld\x00
971 4 (172.16.3.33)
10095 5 (172.16.4.33)
[root@vm4 ~]# cat /etc/redhat-release
CentOS Linux release 7.2.1511 (Core)
[root@vm4 ~]# rpm -q corosync dlm
corosync-2.4.0-9.el7_4.2.x86_64
dlm-4.0.7-1.el7.x86_64
--
saff...@gmail.com
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