RE: Timeout parameters

From: "Tsunakawa, Takayuki" <tsunakawa(dot)takay(at)jp(dot)fujitsu(dot)com>
To: "Nagaura, Ryohei" <nagaura(dot)ryohei(at)jp(dot)fujitsu(dot)com>, "Jamison, Kirk" <k(dot)jamison(at)jp(dot)fujitsu(dot)com>
Cc: 'Michael Paquier' <michael(at)paquier(dot)xyz>, "AYahorau(at)ibagroup(dot)eu" <AYahorau(at)ibagroup(dot)eu>, 'Fabien COELHO' <coelho(at)cri(dot)ensmp(dot)fr>, "'pgsql-hackers(at)postgresql(dot)org'" <pgsql-hackers(at)postgresql(dot)org>, "MikalaiKeida(at)ibagroup(dot)eu" <MikalaiKeida(at)ibagroup(dot)eu>
Subject: RE: Timeout parameters
Date: 2019-02-21 07:56:05
Message-ID: 0A3221C70F24FB45833433255569204D1FB9EDCB@G01JPEXMBYT05
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From: Nagaura, Ryohei [mailto:nagaura(dot)ryohei(at)jp(dot)fujitsu(dot)com]
> > Maybe. Could you suggest good description?
> Clients wait until the socket become readable when they try to get results
> of their query.
> If the socket state get readable, clients read results.
> (See src/interfaces/libpq/fe-exec.c, fe-misc.c)
> The current pg uses poll() to monitor socket states.
> "socket_timeout" is used as timeout argument of poll().
> (See [1] about poll() and its arguments)
> Because "tcp_user_timeout" handles the timeout before and after the above
> procedure,
> there are different monitoring target between "socket_timeout" and
> "tcp_user_timeout".
> When the server is saturated, "statement_timeout" doesn't work while
> "socket_timeout" does work.
> In addition to this, the purpose of "statement_timeout" is to reduce
> server's burden, I think.

OK, I understand your intent. What I asked Kirk-san is to suggest a description for socket_timeout parameter that the user would see in PostgreSQL documentation.

> My proposal is to enable clients to release their resource which is used
> communication w/ the saturated server.

I thought the primary purpose is to prevent applications from hanging too long, so that the user does not have to wait infinitely. Releasing resources is a secondary purpose.

Takayuki Tsunakawa

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