[pgpool-hackers: 3410] Re: watchdog behavior regarding VIP

[Muhammad Usama]

On Tue, Sep 3, 2019 at 7:25 PM Tatsuo Ishii <ishii at sraoss.co.jp> wrote:

> > Hi Ishii-San,
> >
> > On Tue, Sep 3, 2019 at 5:43 AM Tatsuo Ishii <ishii at sraoss.co.jp> wrote:
> >
> >> Hi Usama,
> >>
> >> Can you comment on this:
> >> https://www.pgpool.net/mantisbt/view.php?id=541
> >>
> >> It seems VIP is not set when there's no quorum. Since there's nothing
> >> in the docs regarding VIP vs. quorum and I am wondering if this is
> >> a feature or a bug.
> >>
> >
> > This is a feature and as per the design. The reason for doing this is to
> > avoid split-brain syndrome.
> > In the absence of a quorum, the watchdog cluster does select a master
> node
> > but waits for the quorum to perform the escalation(bringing up of VIP).
> >
> > Initially, in the absence of the quorum, the cluster used to abstain from
> > selecting the master node but it was causing some synchronization issues
> so
> > the behaviour was modified and now the cluster goes on the elect the
> master
> > node even in the absence of the quorum but does not bring up the
> > VIP until it finds the quorum.
> >
> > Below mentioned commit changed the said behaviour back in 2015
> >
> >
> https://git.postgresql.org/gitweb/?p=pgpool2.git;a=commitdiff;h=6238ba9d2aaa82db415b11aca90d54981a854e09
>
> Thanks for the explanation. One more question.
>
> Suppose 3 node watchdog configuration. Initially all 3 nodes are up
> and VIP is up. Now 2 of 3 nodes go down, and quorum is lost, so the
> VIP will be brought down?
>

Yes, as soon as a quorum is lost the master node will perform the
de_escalation and remove the VIP.

Thanks
Best regards
Muhammad Usama


> Best regards,
> --
> Tatsuo Ishii
> SRA OSS, Inc. Japan
> English: http://www.sraoss.co.jp/index_en.php
> Japanese:http://www.sraoss.co.jp
>
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