Re: Patch: Implement failover on libpq connect level.

From: Craig Ringer <craig(at)2ndquadrant(dot)com>
To: Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: "Tsunakawa, Takayuki" <tsunakawa(dot)takay(at)jp(dot)fujitsu(dot)com>, Mithun Cy <mithun(dot)cy(at)enterprisedb(dot)com>, Peter van Hardenberg <pvh(at)pvh(dot)ca>, Peter Eisentraut <peter_e(at)gmx(dot)net>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Patch: Implement failover on libpq connect level.
Date: 2016-11-19 01:23:43
Message-ID: CAMsr+YGuaHDee-8dEn0iH4Vs28WngDxxrQkHJ_H4WSQXFoKf8w@mail.gmail.com
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On 19 November 2016 at 01:29, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:

>> We can and probably should have both.
>>
>> If the server tells us on connect whether it's a standby or not, use that.
>>
>> Otherwise, ask it.
>>
>> That way we don't pay the round-trip cost and get the log spam when
>> talking to newer servers that send us something useful in the startup
>> packet, but we can still query it on older servers. Graceful fallback.
>>
>> Every round trip is potentially very expensive. Having libpq do them
>> unnecessarily is bad.
>
> True, but raising the bar for this feature so that it doesn't get done
> is also bad. It can be improved in a later patch.

Good point. Starting with the followup query method seems fine.

--
Craig Ringer http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services

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