[ClusterLabs] PostgreSQL PAF failover issue

[Jehan-Guillaume de Rorthais]

Hi,

On Fri, 14 Jun 2019 12:27:12 +0200
Tiemen Ruiten <t.ruiten at rdmedia.com> wrote:
> I setup a new 3-node PostgreSQL cluster with HA managed by PAF. Nodes are
> named ph-sql-03, ph-sql-04, ph-sql-05. Archive mode is on and writing
> archive files to an NFS share that's mounted on all nodes using pgBackRest.
> 
> What I did:
> - Create a pacemaker cluster, cib.xml is attached.
> - Set maintenance-mode=true in pacemaker

This is not required. Just build your PgSQL replication, shut down the
instances, then add the PAF resource to the cluster.

But it's not very important here.

> - Bring up ph-sql-03 with pg_ctl start
> - Take a pg_basebackup on ph-sql-04 and ph-sql-05
> - Create a recovery.conf on ph-sql-04 and ph-sql-05:
> 
> standby_mode = 'on'
> primary_conninfo = 'user=replication password=XXXXXXXXXXXXXXXX
> application_name=ph-sql-0x host=10.100.130.20 port=5432 sslmode=prefer
> sslcompression=0 krbsrvname=postgres target_session_attrs=any'
> recovery_target_timeline = 'latest'
> restore_command = 'pgbackrest --stanza=pgdb2 archive-get %f "%p"'

Sounds fine.

> - Bring up ph-sql-04 and ph-sql-05 and let recovery finish
> - Set maintenance-mode=false in pacemaker
> - Cluster is now running with ph-sql-03 as master and ph-sql-04/5 as slaves
> At this point I tried a manual failover:
> - pcs resource move --wait --master pgsql-ha ph-sql-04
> Contrary to my expectations, pacemaker attempted to stop psqld on
> ph-sql-03.

Indeed. PostgreSQL doesn't support hot-demote. It has to be shut downed and
started as a standby.

> This took longer than the configured timeout of 60s (checkpoint
> hadn't completed yet) and the node was fenced.

60s of checkpoint during a maintenance window? That's important indeed. I would
command doing a manual checkpoint before triggering the move/switchover.

> Then I ended up with
> ph-sql-04 and ph-sql-05 both in slave mode and ph-sql-03 rebooting.
> 
>  Master: pgsql-ha
>   Meta Attrs: notify=true
>   Resource: pgsqld (class=ocf provider=heartbeat type=pgsqlms)
>    Attributes: bindir=/usr/pgsql-11/bin pgdata=/var/lib/pgsql/11/data
> recovery_template=/var/lib/pgsql/recovery.conf.pcmk
>    Operations: demote interval=0s timeout=30s (pgsqld-demote-interval-0s)
>                methods interval=0s timeout=5 (pgsqld-methods-interval-0s)
>                monitor interval=15s role=Master timeout=10s
> (pgsqld-monitor-interval-15s)
>                monitor interval=16s role=Slave timeout=10s
> (pgsqld-monitor-interval-16s)
>                notify interval=0s timeout=60s (pgsqld-notify-interval-0s)
>                promote interval=0s timeout=30s (pgsqld-promote-interval-0s)
>                reload interval=0s timeout=20 (pgsqld-reload-interval-0s)
>                start interval=0s timeout=60s (pgsqld-start-interval-0s)
>                stop interval=0s timeout=60s (pgsqld-stop-interval-0s)
> 
> I understand I should at least increase the timeout of the stop operation
> for psqld, though I'm not sure how much. Checkpoints can take up to 15
> minutes to complete on this cluster. So is 20 minutes reasonable? 

20 minutes is not reasonable for HA. 2 minutes is for manual procedure.
Timeout are here so the cluster knows how to react during unexpected failure.
Not during maintenance.

As I wrote, just add a manual checkpoint in your switchover procedure before
the actual move.

> Any other operations I should increase the timeouts for?
> 
> Why didn't pacemaker elect and promote one of the other nodes?

Do you have logs of all nodes during this time period?