[pgpool-general: 7553] Re: Strange behavior on switchover with detach_false_primary enabled

[Tatsuo Ishii]

If both of Pgpool+PostgreSQL go down on a server, there's only 1
PostgreSQL in the cluster and detach_false_primary is meaningless
anyway (it runs but does nothing). In other case the same discussion
applies.

>> 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.

> 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
>> _______________________________________________
>> pgpool-general mailing list
>> pgpool-general at pgpool.net
>> http://www.pgpool.net/mailman/listinfo/pgpool-general
>>
> 
> -- 
> anssi at iki.fi
> _______________________________________________
> pgpool-general mailing list
> pgpool-general at pgpool.net
> http://www.pgpool.net/mailman/listinfo/pgpool-general