[ClusterLabs] Can a two node cluster start resources if only one node is booted?

[john tillman]

> On 20.04.2022 19:53, john tillman wrote:
>> I have a two node cluster that won't start any resources if only one
>> node
>> is booted; the pacemaker service does not start.
>>
>> Once the second node boots up, the first node will start pacemaker and
>> the
>> resources are started.  All is well.  But I would like the resources to
>> start when the first node boots by itself.
>>
>> I thought the problem was with the wait_for_all option but I have it set
>> to "0".
>>
>> On the node that is booted by itself, when I run "corosync-quorumtool" I
>> see:
>>
>>    [root at test00 ~]# corosync-quorumtool
>>    Quorum information
>>    ------------------
>>    Date:             Wed Apr 20 16:05:07 2022
>>    Quorum provider:  corosync_votequorum
>>    Nodes:            1
>>    Node ID:          1
>>    Ring ID:          1.2f
>>    Quorate:          Yes
>>
>>    Votequorum information
>>    ----------------------
>>    Expected votes:   2
>>    Highest expected: 2
>>    Total votes:      1
>>    Quorum:           1
>>    Flags:            2Node Quorate
>>
>>    Membership information
>>    ----------------------
>>        Nodeid      Votes Name
>>             1          1 test00 (local)
>>
>>
>> My config file look like this:
>>    totem {
>>        version: 2
>>        cluster_name: testha
>>        transport: knet
>>        crypto_cipher: aes256
>>        crypto_hash: sha256
>>    }
>>
>>    nodelist {
>>        node {
>>            ring0_addr: test00
>>            name: test00
>>            nodeid: 1
>>        }
>>
>>        node {
>>            ring0_addr: test01
>>            name: test01
>>            nodeid: 2
>>        }
>>    }
>>
>>    quorum {
>>        provider: corosync_votequorum
>>        two_node: 1
>>        wait_for_all: 0
>>    }
>>
>>    logging {
>>        to_logfile: yes
>>        logfile: /var/log/cluster/corosync.log
>>        to_syslog: yes
>>        timestamp: on
>>        debug: on
>>        syslog_priority: debug
>>        logfile_priority: debug
>>    }
>>
>> Fencing is disabled.
>>
>
> That won't work.
>
>> I've also looked in "corosync.log" but I don't know what to look for to
>> diagnose this issue.  I mean there are many lines similar to:
>> [QUORUM] This node is within the primary component and will provide
>> service.
>> and
>> [VOTEQ ] Sending quorum callback, quorate = 1
>> and
>> [VOTEQ ] flags: quorate: Yes Leaving: No WFA Status: No First: Yes
>> Qdevice: No QdeviceAlive: No QdeviceCastVote: No QdeviceMasterWins: No
>>
>> Is there something specific I should look for in the log?
>>
>> So can a two node cluster work after booting only one node?  Maybe it
>> never will and I am wasting a lot of time, yours and mine.
>>
>> If it can, what else can I investigate further?
>>
>
> Before node can start handling resources it needs to know status of
> other node. Without successful fencing there is no way to accomplish it.
>
> Yes, you can tell pacemaker to ignore unknown status. Depending on your
> resources this could simply prevent normal work or lead to data
> corruption.


Makes sense.  Thank you.

Perhaps some future enhancement could allow for this situation?  I mean,
It might be desirable for some cases to allow for a single node to boot,
determine quorum by two_node=1 and wait_for_all=0, and start resources
without ever seeing the other node.  Sure, there are dangers of split
brain but I can see special cases where I want the node to work alone for
a period of time despite the danger.

Thank you again.


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