[pgpool-general: 7552] Re: Strange behavior on switchover with detach_false_primary enabled

[Anssi Kanninen]

No, I was talking about w nodes which both have Pgpool+PostgreSQL.
But I need to set enable_consensus_with_half_votes = on if I want to have 
VIP up with one node.

On Wed, 5 May 2021, Tatsuo Ishii wrote:

>> On Wed, 5 May 2021, Tatsuo Ishii wrote:
>>
>>>> Excellent job guys!
>>>> Does this fix affect on 2-node cluster behaviour?
>>>
>>> I think it does not.
>>>
>>> If both 2-node are up, then the cluster behavior will not change
>>> because the quorum exists. If one of the nodes is down,
>>> detach_false_primary is meaningless anyway.
>>
>> What if we have enable_consensus_with_half_votes = on ?
>
> I thought you are talking about there are only two servers and
> pgpool/PostgreSQL are running on each server. Now I realize that you
> are talking about the configuration in which pgpool and PostgreSQL are
> running on separate servers. Ok, let's see...
>
> If enable_consensus_with_half_votes = on, there's a possibility of
> split brain. In the worst case detach_false_primary will run on each
> pgpool node. However this is same as what current detach_false_primary
> is doing anyway. On the other hand, one of pgpool actually goes down,
> detach_false_primary will run on the live pgpool, again which is same
> as today.
>
> If enable_consensus_with_half_votes = off, there will be difference
> when one of pgpool goes down because the quorum will be lost and
> detach_false_primary will not run. However if the quorum is lost, VIP
> will be lost and whole DB service is lost. I don't think anyone cares
> about detach_false_primary in this case.
>
> 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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-- 
anssi at iki.fi