[pgpool-general: 8896] Re: Delegate IP on a single node cluster

[Bo Peng]

Hi,

If you are using Pgpool-II 4.3 or later, you can use
"dynamic cluster membership" to remove the DOWN node from the cluster
to ensure the cluster has quorum and VIP is available.

[dynamic cluster membership]
https://www.pgpool.net/docs/latest/en/html/runtime-watchdog-config.html#CONFIG-WATCHDOG-CLUSTER-MEMBERSHIP

However, using the dynamic cluster membership has an associated risk of
causing a split-brain. So it is strongly recommended to carefully review
if the setup requires the dynamic cluster membership and consider using
conservative values for related settings.

On Tue, 25 Jul 2023 21:35:41 -0600
Steeve Boulanger <sboulanger29 at gmail.com> wrote:

> Greetings,
> 
> We recently had a scenario where 2 nodes out of 3 became unavailable, and
> we were left with a single node (Primary). As a result, the delegate IP was
> not assigned to the Leader /Primary node due to loss of quorum (from my
> understanding). Since all our applications are configured to use the
> delegate IP, we experience an unplanned outage.
> 
> My question is: is there a way to avoid an outage in this specific case? ie
> only a single node available? Or in other words, is it possible to have
> pgpool assign the delegate IP, even when it doesn't have a quorum?
> 
> Regards,
> Steeve


-- 
Bo Peng <pengbo at sraoss.co.jp>
SRA OSS LLC
TEL: 03-5979-2701 FAX: 03-5979-2702
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