RE: Timeout parameters

From: "Tsunakawa, Takayuki" <tsunakawa(dot)takay(at)jp(dot)fujitsu(dot)com>
To: 'Fabien COELHO' <coelho(at)cri(dot)ensmp(dot)fr>, "Nagaura, Ryohei" <nagaura(dot)ryohei(at)jp(dot)fujitsu(dot)com>
Cc: "'pgsql-hackers(at)postgresql(dot)org'" <pgsql-hackers(at)postgresql(dot)org>, "AYahorau(at)ibagroup(dot)eu" <AYahorau(at)ibagroup(dot)eu>
Subject: RE: Timeout parameters
Date: 2018-12-27 08:25:06
Message-ID: 0A3221C70F24FB45833433255569204D1FB5E336@G01JPEXMBYT05
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From: Fabien COELHO [mailto:coelho(at)cri(dot)ensmp(dot)fr]
> I still do not understand the use-case specifics: for me, aborting the
> connection, or a softer cancelling the statement, will result in the
> server stopping the statement, so the server does NOT "continue the job",
> so I still do not see how it really differs from the server-side
> statement_timeout setting.

How about when the server is so saturated that statement_timeout cannot work? See SQLNET.SEND_TIMEOUT and SQLNET.RECV_TIMEOUT here:

https://docs.oracle.com/cd/E11882_01/network.112/e10835/sqlnet.htm#NETRF228

As these parameter names suggest, maybe we could use SEND_TIMEO and RECV_TIMEO socket options for setsockopt() instead of using pqWaitTimed().

To wrap up, the relevant parameters work like this:

* TCP keepalive and TCP user (retransmission) timeout: for network problems
* statement_timeout: for long-running queries
* socket_timeout (or send/recv_timeout): for saturated servers

FYI, PgJDBC has a parameter named socketTimeout:

https://jdbc.postgresql.org/documentation/head/connect.html#connection-parameters

Regards
Takayuki Tsunakawa

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