[ClusterLabs] Stopping the last node with pcs

[Tomas Jelinek]

Hi,

sorry for the late answer and thanks everyone who already responded.

This feature was implemented a long time ago based on
https://bugzilla.redhat.com/show_bug.cgi?id=1180506
The request was: pcs cluster stop -> this operation should verify if 
removing a node from the cluster will cause loss of quorum and abort. Of 
course we want to allow a manual override.

And that's what we did.

The idea is to warn users that by stopping specified node(s) or the 
local node, the cluster will lose quorum and stop all resources. If the 
last node is being stopped, then obviously all resources will be 
stopped. The wording of the message could be improved in this case. But 
in general, I agree with Ken and lean towards keeping the behavior.

As Ulrich pointed out, 'pcs cluster stop --all' doesn't check for quorum 
loss, since the user made it clear (by specifying --all), that they want 
to stop the whole cluster.

Regards,
Tomas


Dne 28. 04. 21 v 17:41 Digimer napsal(a):
> On 2021-04-28 10:10 a.m., Ken Gaillot wrote:
>> On Tue, 2021-04-27 at 23:23 -0400, Digimer wrote:
>>> Hi all,
>>>
>>>    I noticed something odd.
>>>
>>> ====
>>> [root at an-a02n01 ~]# pcs cluster status
>>> Cluster Status:
>>>   Cluster Summary:
>>>     * Stack: corosync
>>>     * Current DC: an-a02n01 (version 2.0.4-6.el8_3.2-2deceaa3ae) -
>>> partition with quorum
>>>     * Last updated: Tue Apr 27 23:20:45 2021
>>>     * Last change:  Tue Apr 27 23:12:40 2021 by root via cibadmin on
>>> an-a02n01
>>>     * 2 nodes configured
>>>     * 12 resource instances configured (4 DISABLED)
>>>   Node List:
>>>     * Online: [ an-a02n01 ]
>>>     * OFFLINE: [ an-a02n02 ]
>>>
>>> PCSD Status:
>>>    an-a02n01: Online
>>>    an-a02n02: Offline
>>> ====
>>> [root at an-a02n01 ~]# pcs cluster stop
>>> Error: Stopping the node will cause a loss of the quorum, use --force
>>> to
>>> override
>>> ====
>>>
>>>    Shouldn't pcs know it's the last node and shut down without
>>> complaint?
>>
>> It knows, it's just not sure you know :)
>>
>> pcs's design philosophy is to hand-hold users by default and give
>> expert users --force.
>>
>> The idea in this case is that (especially in 3-to-5-node clusters)
>> someone might not realize that stopping one node could make all
>> resources stop cluster-wide.
> 
> This makes total sense in 3+ node cluster. However, when you're asking
> the last node in a two-node cluster to stop, then it seems odd. Perhaps
> overriding this behaviour when 2-node is set?
> 
> In any case, I'm calling this from a program and that means I need to
> use '--force' all the time (or add some complex logic of my own, which I
> can do).
> 
> Well anyway, now I know it was intentional. :)
>