Re: Proposal: recent access based routing for primary-replica setups

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From: Tatsuo Ishii <[email protected]>
To: [email protected]
Cc: [email protected]
Subject: Re: Proposal: recent access based routing for primary-replica setups
Date: Fri, 31 Oct 2025 08:45:26 +0900 (JST)
Message-ID: <[email protected]> (raw)
In-Reply-To: <CACeKOO2W09UBbE5erXQeCDRBSbW8gK=9AsMVddRbX0dWaXKtig@mail.gmail.com>
References: <CACeKOO2voMe_OnJYThSdE8jZBAWjOj3Z2KJTb8_8-87AbaO7eg@mail.gmail.com>
	<[email protected]>
	<CACeKOO2W09UBbE5erXQeCDRBSbW8gK=9AsMVddRbX0dWaXKtig@mail.gmail.com>

> Hi,
> 
> I'm back at work - wdyt of this version?

Thanks for the patch! I will look into it weekend.

> (side note - Japan was incredible :))

Glad to hear that!

> On Tue, Sep 30, 2025 at 12:35 PM Tatsuo Ishii <[email protected]> wrote:
> 
>> > I would actually suggest including down state instances in case pgpool
>> > isn’t aware yet. It can exclude them once it does.
>> > For these cases maybe  -1 ?
>>
>> I don't think pgpool will triger failover even if
>> replication_delay_source_cmd returns -1 for such instance because
>> pgpool already has its own method to detect instance down (i.e. health
>> check) and method to avoid false positive
>> (i.e. failover_require_consensus).
>>
>> Still for such instaces replication_delay_source_cmd returns -1 maybe
>> useful if it's logged for admins.
>>
>> So I am Okay with the idea.
>>
>> Best regards,
>> --
>> Tatsuo Ishii
>> SRA OSS K.K.
>> English: http://www.sraoss.co.jp/index_en/
>> Japanese:http://www.sraoss.co.jp
>>
>> > Nadav Shatz
>> > Tailor Brands | CTO
>> >
>> >
>> > On Mon, Sep 22, 2025 at 7:34 AM Tatsuo Ishii <[email protected]>
>> wrote:
>> >
>> >> > Thank you for the kind words. We are having a great time!
>> >>
>> >> Glad to hear that!
>> >>
>> >> > Regarding the command knowing about the primary I think it is safe to
>> >> assume.
>> >>
>> >> Okay.
>> >>
>> >> > We can start this way and evolve in the future if needed.
>> >>
>> >> Agreed.
>> >>
>> >> > I can include a note about it in the notes that the command will only
>> >> receive the secondary instances as arguments.
>> >> >
>> >> > Anything else that comes to mind?
>> >>
>> >> Sounds like a reasonable requirement. Also the command excludes any
>> >> instance which is in down state?
>> >>
>> >> Best regards,
>> >> --
>> >> Tatsuo Ishii
>> >> SRA OSS K.K.
>> >> English: http://www.sraoss.co.jp/index_en/
>> >> Japanese:http://www.sraoss.co.jp
>> >>
>> >> > Nadav Shatz
>> >> > CTO
>> >> >
>> >> >> On Sep 16, 2025, at 7:30 PM, Tatsuo Ishii <[email protected]>
>> wrote:
>> >> >>
>> >> >> 
>> >> >>>
>> >> >>> Hi Tatsuo,
>> >> >>>
>> >> >>> Sorry for the late reply - I'm traveling with my family at the
>> moment
>> >> (in
>> >> >>> Japan actually)
>> >> >>
>> >> >> Excellent! Hope you and your family are spending great time in Japan.
>> >> >>
>> >> >>> and might be delayed in responding.
>> >> >>
>> >> >> No problem at all. I think you should focus on the travel at this
>> >> >> moment.
>> >> >>
>> >> >>> Re your points:
>> >> >>> 1 - we can, but I have to say that a user I tend to prefer
>> >> configuration
>> >> >>> values not have a "magic" value that does something different than
>> the
>> >> >>> usual case like this would create. I'd stick with what we already
>> have
>> >> >>> planned. happy to hear from others on the mailing list as well of
>> >> course.
>> >> >>
>> >> >> Makes sense. I withdraw my proposal.
>> >> >>
>> >> >>> 2 - I think we can have the primary always be the first or we can
>> >> >>> completely remove it since it might be redundant as it's always
>> going
>> >> to be
>> >> >>> 0. what do you think?
>> >> >>
>> >> >> What I am not sure is, whether we can assume the command always knows
>> >> >> which host (or IP) is primary? If the answer is yes, then we could
>> >> >> omit the primary. What do you think?
>> >> >>
>> >> >>> 3 - I agree with you, next version (after we clear everything else)
>> >> will
>> >> >>> have only ip/hostname+port.
>> >> >>
>> >> >> Thank you for understanding.
>> >> >>
>> >> >>> Let me know your thoughts
>> >> >>>
>> >> >>> Thanks!
>> >> >>>
>> >> >>>> On Tue, Sep 9, 2025 at 9:42 AM Tatsuo Ishii <[email protected]>
>> >> wrote:
>> >> >>>>
>> >> >>>> Hi Nadav,
>> >> >>>>
>> >> >>>>> Hi Tatsuo,
>> >> >>>>>
>> >> >>>>> Please find attached the 3 patch files (implementation, tests,
>> docs)
>> >> with
>> >> >>>>> the updates we discussed.
>> >> >>>>>
>> >> >>>>> What do you think?
>> >> >>>>
>> >> >>>> I haven't read the code details yet but I have a few questions.
>> >> >>>>
>> >> >>>> 1) Can we use only replication_delay_source_cmd and if it's value
>> is
>> >> >>>>   'builtin', then we treat it as replication_delay_source =
>> builtin?
>> >> >>>>   Maybe this is matter of taste but I would like to know your
>> >> >>>>   opinion.
>> >> >>>>
>> >> >>>> 2) replication_delay_source_cmd will be given an ordered list of
>> >> >>>>   instance identifiers. But it seems there's no way for the command
>> >> >>>>   which one is the primary instance. Is it okay for the command?
>> >> >>>>
>> >> >>>> 3) Why do you have 3 kind of instance identifiers (application
>> name,
>> >> >>>>   hostname (IP) + port and node id? I thought "hostname (IP) +
>> port"
>> >> >>>>   is sufficient.
>> >> >>>>
>> >> >>>> Comments?
>> >> >>>> --
>> >> >>>> Tatsuo Ishii
>> >> >>>> SRA OSS K.K.
>> >> >>>> English: http://www.sraoss.co.jp/index_en/
>> >> >>>> Japanese:http://www.sraoss.co.jp
>> >> >>>>
>> >> >>>
>> >> >>>
>> >> >>> --
>> >> >>> Nadav Shatz
>> >> >>> Tailor Brands | CTO
>> >> >
>> >> >
>> >>
>>
> 
> 
> -- 
> Nadav Shatz
> Tailor Brands | CTO

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