[pgpool-general: 8454] Re: Watchdog using only 2 nodes

[Jesús Campoy]

Thank you for your quick response. It works!

El mar, 11 oct 2022 a las 9:45, Bo Peng (<pengbo at sraoss.co.jp>) escribió:

> Hello,
>
> > Should I discard the use of watchdog? Is there any possibility to make it
> > work with only 2 nodes?
>
> If you are using Pgpool-II with two Pgpool-II nodes,
> you need to enable the following parameter to ensure that VIP is up even
> if one node goes down.
>
>   enable_consensus_with_half_votes = on
>
>
> https://www.pgpool.net/docs/43/en/html/runtime-watchdog-config.html#GUC-ENABLE-CONSENSUS-WITH-HALF-VOTES
>
> Plase note that enabling this parameter may cause split-brain.
>
>
> On Tue, 11 Oct 2022 09:26:54 +0200
> Jesús Campoy <jesuscampoy at gmail.com> wrote:
>
> > 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
>
>
> --
> Bo Peng <pengbo at sraoss.co.jp>
> SRA OSS LLC
> https://www.sraoss.co.jp/
>
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