[pgpool-general: 8451] Watchdog using only 2 nodes

[Jesús Campoy]

Hi all,

I'm trying to configure watchdog in pgpool version 4.3.2 (tamahomeboshi)
using streaming replication with two nodes, one as primary and another as
standby.
But I just read in the documentation that to use watchdog requires at least
3 nodes. As I mentioned, I have only 2 nodes and I don't have the
possibility to add a third one.
Should I discard the use of watchdog? Is there any possibility to make it
work with only 2 nodes?

4.1. Introduction

Watchdog is a sub process of Pgpool-II to add high availability. Watchdog
is used to resolve the single point of failure by coordinating multiple
Pgpool-II nodes. The watchdog was first introduced in pgpool-II V3.2 and is
significantly enhanced in Pgpool-II V3.5, to ensure the presence of a
quorum at all time. This new addition to watchdog makes it more fault
tolerant and robust in handling and guarding against the split-brain
syndrome and network partitioning. In addition, V3.7 introduced quorum
failover (see Section 5.14.6
<https://www.pgpool.net/docs/42/en/html/runtime-watchdog-config.html#CONFIG-WATCHDOG-FAILOVER-BEHAVIOR>)
to reduce the false positives of PostgreSQL server failures. To ensure the
quorum mechanism properly works, the number of Pgpool-II nodes must be odd
in number and greater than or equal to 3.
delegate_IP (string)

Specifies the virtual IP address (VIP) of Pgpool-II that is connected from
client servers (application servers etc.). When a Pgpool-II is switched
from standby to active, the Pgpool-II takes over this VIP. VIP will not be
brought up in case the quorum does not exist. Default is ''(empty): which
means virtual IP will never be brought up.

This parameter can only be set at server start.

Thanks in advance.

Best,
Jesús
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