Message-ID: <1e9012b85ffaf04efb13859465804ce9b08ce073.camel@cybertec.at>
Subject: Re: [HACKERS] psql casts aspersions on server reliability
From: Laurenz Albe <laurenz.albe@cybertec.at>
To: Bruce Momjian <bruce@momjian.us>, Tom Lane <tgl@sss.pgh.pa.us>
Cc: Robert Haas <robertmhaas@gmail.com>, "pgsql-hackers@postgresql.org"
	 <pgsql-hackers@postgresql.org>
Date: Fri, 24 Nov 2023 04:06:22 +0100
In-Reply-To: <ZV957kbJfJ4BiTKU@momjian.us>
References: 
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	 <15946.1475068481@sss.pgh.pa.us> <ZV6Yvb5mu5VDRkfl@momjian.us>
	 <2543635.1700699932@sss.pgh.pa.us> <ZV7GGrOHxUgqygA6@momjian.us>
	 <ZV957kbJfJ4BiTKU@momjian.us>
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On Thu, 2023-11-23 at 11:12 -0500, Bruce Momjian wrote:
> On Wed, Nov 22, 2023 at 10:25:14PM -0500, Bruce Momjian wrote:
> > Yes, you are correct.  Here is a patch that implements the FATAL test,
> > though I am not sure I have the logic correct or backwards, and I don't
> > know how to test this.  Thanks.
>=20
> I developed the attached patch which seems to work better.  In testing
> kill -3 on a backend or calling elog(FATAL) in the server for a
> session, libpq's 'res' is NULL, meaning we don't have any status to
> check for PGRES_FATAL_ERROR.  It is very possible that libpq just isn't
> stuctured to have the PGRES_FATAL_ERROR at the point where we issue this
> message, and this is not worth improving.
>=20
> 	test=3D> select pg_sleep(100);
> -->	FATAL:  FATAL called
> =09
> 	server closed the connection unexpectedly
> -->	        This probably means the server terminated null
> 	        before or while processing the request.
> 	The connection to the server was lost. Attempting reset: Succeeded.

I don't thing "terminated null" is a meaningful message.

>  	libpq_append_conn_error(conn, "server closed the connection unexpectedl=
y\n"
> -							"\tThis probably means the server terminated abnormally\n"
> -							"\tbefore or while processing the request.");
> +							"\tThis probably means the server terminated%s\n"
> +							"\tbefore or while processing the request.",
> +							(conn->result =3D=3D NULL) ? " null" :
> +							(conn->result->resultStatus =3D=3D PGRES_FATAL_ERROR) ?
> +							"" : " abnormally");

Apart from the weird "null", will that work well for translation?

> --- a/src/interfaces/libpq/fe-protocol3.c
> +++ b/src/interfaces/libpq/fe-protocol3.c
> @@ -2158,6 +2158,7 @@ pqFunctionCall3(PGconn *conn, Oid fnid,
>  				if (pqGetErrorNotice3(conn, true))
>  					continue;
>  				status =3D PGRES_FATAL_ERROR;
> +				fprintf(stderr, "Got 'E'\n");
>  				break;
>  			case 'A':			/* notify message */
>  				/* handle notify and go back to processing return values */

That looks like a leftover debugging message.

Yours,
Laurenz Albe