[pgpool-general: 8452] Re: Watchdog using only 2 nodes

[Jesús Campoy]

To clarify, my problem is that I always need a virtual IP (indicated in
odbc.ini file) where clients connect to the database.
Although I had the possibility to have the third node, in my system
sometimes there is only one server running. How should I ensure that the
virtual IP is up in this case?

Thank you.

El mar, 11 oct 2022 a las 9:26, Jesús Campoy (<jesuscampoy at gmail.com>)
escribió:

> 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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