[ClusterLabs] Antw: Re: Antw: [EXT] Non recoverable state of cluster after exit of one node due to killing of processes by oom killer

[Ulrich Windl]

>>> shivraj dongawe <shivraj198 at gmail.com> schrieb am 15.02.2021 um 08:27 in
Nachricht
<CALpaHO_6LsYM=t76CifsRkFeLYDKQc+hY3kz7PRKp7b4se=-Aw at mail.gmail.com>:
> Fencing is done using fence_scsi.
> Config details are as follows:
>  Resource: scsi (class=stonith type=fence_scsi)
>   Attributes: devices=/dev/mapper/mpatha pcmk_host_list="node1 node2"
> pcmk_monitor_action=metadata pcmk_reboot_action=off
>   Meta Attrs: provides=unfencing
>   Operations: monitor interval=60s (scsi-monitor-interval-60s)
> 
> On Mon, Feb 15, 2021 at 7:17 AM Ulrich Windl <
> Ulrich.Windl at rz.uni-regensburg.de> wrote:
> 
>> >>> shivraj dongawe <shivraj198 at gmail.com> schrieb am 14.02.2021 um 12:03
>> in
>> Nachricht
>> <CALpaHO--3ERfwST70mBL-Wm9g6yH3YtD-wDA1r_CKnbrsxu4Sg at mail.gmail.com>:
>> > We are running a two node cluster on Ubuntu 20.04 LTS. Cluster related
>> > package version details are as
>> > follows: pacemaker/focal-updates,focal-security 2.0.3-3ubuntu4.1 amd64
>> > pacemaker/focal 2.0.3-3ubuntu3 amd64
>> > corosync/focal 3.0.3-2ubuntu2 amd64
>> > pcs/focal 0.10.4-3 all
>> > fence-agents/focal 4.5.2-1 amd64
>> > gfs2-utils/focal 3.2.0-3 amd64
>> > dlm-controld/focal 4.0.9-1build1 amd64
>> > lvm2-lockd/focal 2.03.07-1ubuntu1 amd64
>> >
>> > Cluster configuration details:
>> > 1. Cluster is having a shared storage mounted through gfs2 filesystem
>> with
>> > the help of dlm and lvmlockd.
>> > 2. Corosync is configured to use knet for transport.
>> > 3. Fencing is configured using fence_scsi on the shared storage which is
>> > being used for gfs2 filesystem
>> > 4. Two main resources configured are cluster/virtual ip and
>> postgresql-12,
>> > postgresql-12 is configured as a systemd resource.
>> > We had done failover testing(rebooting/shutting down of a node, link
>> > failure) of the cluster and had observed that resources were getting
>> > migrated properly on the active node.
>> >
>> > Recently we came across an issue which has occurred repeatedly in span of
>> > two days.
>> > Details are below:
>> > 1. Out of memory killer is getting invoked on active node and it starts
>> > killing processes.
>> > Sample is as follows:
>> > postgres invoked oom-killer: gfp_mask=0x100cca(GFP_HIGHUSER_MOVABLE),
>> > order=0, oom_score_adj=0
>> > 2. At one instance it started with killing of pacemaker and on another
>> with
>> > postgresql. It does not stop with the killing of a single process it goes
>> > on killing others(more concerning is killing of cluster related
>> processes)
>> > as well. We have observed that swap space on that node is 2 GB against
>> RAM
>> > of 96 GB and are in the process of increasing swap space to see if this
>> > resolves this issue. Postgres is configured with shared_buffers value of
>> 32
>> > GB(which is way less than 96 GB).
>> > We are not yet sure which process is eating up that much memory suddenly.
>> > 3. As a result of killing processes on node1, node2 is trying to fence
>> > node1 and thereby initiating stopping of cluster resources on node1.
>>
>> How is fencing being done?
>>
>> > 4. At this point we go in a stage where it is assumed that node1 is down
>> > and application resources, cluster IP and postgresql are being started on
>> > node2.

This is why I was asking: Is your fencing successful ("assumed that node1 is down
"), or isn't it?

>> > 5. Postgresql on node 2 fails to start in 60 sec(start operation timeout)
>> > and is declared as failed. During the start operation of postgres, we
>> have
>> > found many messages related to failure of fencing and other resources
>> such
>> > as dlm and vg waiting for fencing to complete.
>> > Details of syslog messages of node2 during this event are attached in
>> file.
>> > 6. After this point we are in a state where node1 and node2 both go in
>> > fenced state and resources are unrecoverable(all resources on both
>> nodes).
>> >
>> > Now my question is out of memory issue of node1 can be taken care by
>> > increasing swap and finding out the process responsible for such huge
>> > memory usage and taking necessary actions to minimize that memory usage,
>> > but the other issue that remains unclear is why cluster is not shifted to
>> > node2 cleanly and become unrecoverable.
>>
>>
>>
>>
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