From: "Hayato Kuroda (Fujitsu)" <kuroda.hayato@fujitsu.com>
To: 'Kyotaro Horiguchi' <horikyota.ntt@gmail.com>
CC: "katsuragiy@oss.nttdata.com" <katsuragiy@oss.nttdata.com>,
	"yuzhihong@gmail.com" <yuzhihong@gmail.com>, "tgl@sss.pgh.pa.us"
	<tgl@sss.pgh.pa.us>, "vignesh21@gmail.com" <vignesh21@gmail.com>,
	"pgsql-hackers@lists.postgresql.org" <pgsql-hackers@lists.postgresql.org>,
	"onderkalaci@gmail.com" <onderkalaci@gmail.com>,
	"masao.fujii@oss.nttdata.com" <masao.fujii@oss.nttdata.com>,
	"Shinya11.Kato@oss.nttdata.com" <Shinya11.Kato@oss.nttdata.com>
Subject: RE: [Proposal] Add foreign-server health checks infrastructure
Thread-Topic: [Proposal] Add foreign-server health checks infrastructure
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Date: Thu, 9 Feb 2023 14:38:30 +0000
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Dear Horiguchi-san,

Thank you for checking! The patch will be attached to another mail.

> At Fri, 27 Jan 2023 06:57:01 +0000, "Hayato Kuroda (Fujitsu)"
> <kuroda.hayato@fujitsu.com> wrote in
> > I found cfbot failure, PSA fixed version.
>=20
> +       Unlike <xref linkend=3D"libpq-PQstatus"/>, this function checks s=
ocket
> +       health. This check is performed by polling the socket. This funct=
ion is
> +       currently available only on systems that support the non-standard
> +       <symbol>POLLRDHUP</symbol> extension to the
> <symbol>poll</symbol> system
>=20
> I find it quite confusing that we have pqSocketCheck and PQconnCheck,
> that does almost the same thing.. Since pqSocketCheck is a static
> function, we can modify the function as we like.

Renamed to pqSocketIsReadableOrWritableOrValid(), but seemed very bad...

> I still don't understand why we need pqconnCheck_internal separate
> from pqSocketPoll(), and PQconnCheck from pqSocketCheck.

pqconnCheck_internal() was combined into pqSocketPoll(), but PQconnCheck() =
still
exists. libpq-fe.h, did not include standard header files except stdio.h. I=
'm not
sure whether we can add an inclusion of time.h, because it may break the co=
mpatibility
that some platform may not have the header. If there are not such a system,=
 we may
able to export pqSocketCheck() and remove PQconnCheck().

The side effect of this changes is that codes become dirty when we add kque=
ue() support...

> https://www.postgresql.org/message-id/flat/TYAPR01MB58665BF23D38EDF1
> 0028DE2AF5299%40TYAPR01MB5866.jpnprd01.prod.outlook.com#47d21431bf9
> fa94f763c824f6e81fa54
> > IIUC, pqSocketCheck () calls pqSocketPoll(),
> > and in the pqSocketPoll() we poll()'d the POLLIN or POLLOUT event.
> > But according to [1], we must wait POLLRDHUP event,
> > so we cannot reuse it straightforward.
>=20
> Yeah, I didn't suggest to use the function as-is. Couldn't we extend
> the fucntion by letting it accept end_time =3D 0 && !forRead &&
> !forWrite, not causing side effects?

Modified accordingly. Is it what you expected?

Best Regards,
Hayato Kuroda
FUJITSU LIMITED