[ClusterLabs] Corosync lost quorum but DLM still gives locks

[Jean-Marc Saffroy]

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 at 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 at 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 at 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 at vm4 ~]# cat /etc/redhat-release 
CentOS Linux release 7.2.1511 (Core) 

[root at vm4 ~]# rpm -q corosync dlm
corosync-2.4.0-9.el7_4.2.x86_64
dlm-4.0.7-1.el7.x86_64

-- 
saffroy at gmail.com