Date: Thu, 23 Nov 2023 11:12:30 -0500
From: Bruce Momjian <bruce@momjian.us>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Robert Haas <robertmhaas@gmail.com>,
	"pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
Subject: Re: [HACKERS] psql casts aspersions on server reliability
Message-ID: <ZV957kbJfJ4BiTKU@momjian.us>
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On Wed, Nov 22, 2023 at 10:25:14PM -0500, Bruce Momjian wrote:
> On Wed, Nov 22, 2023 at 07:38:52PM -0500, Tom Lane wrote:
> > Bruce Momjian <bruce@momjian.us> writes:
> > > On Wed, Sep 28, 2016 at 09:14:41AM -0400, Tom Lane wrote:
> > >> I could go along with just dropping the last sentence ("This probably...")
> > >> if the last error we got was FATAL level.  I don't find "unexpectedly"
> > >> to be problematic here: from the point of view of psql, and probably
> > >> of its user, the shutdown *was* unexpected.
> > 
> > > I looked at this thread from 2016 and I think the problem is the
> > > "abnormally" word, since if the server was shutdown by the administrator
> > > (most likely), it isn't abnormal.  Here is a patch to remove
> > > "abnormally".
> > 
> > I do not think this is an improvement.  The places you are changing
> > are reacting to a connection closure.  *If* we had previously gotten a
> > "FATAL: terminating connection due to administrator command" message,
> > then yeah the connection closure is expected; but if not, it isn't.
> > Your patch adds no check for that.  (As I remarked in 2016, we could
> > probably condition this on the elevel being FATAL, rather than
> > checking for specific error messages.)
> 
> 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.

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.

	test=> select pg_sleep(100);
-->	FATAL:  FATAL called
	
	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.

-- 
  Bruce Momjian  <bruce@momjian.us>        https://momjian.us
  EDB                                      https://enterprisedb.com

  Only you can decide what is important to you.

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diff --git a/src/interfaces/libpq/fe-misc.c b/src/interfaces/libpq/fe-misc.c
index 660cdec93c..64faad19df 100644
--- a/src/interfaces/libpq/fe-misc.c
+++ b/src/interfaces/libpq/fe-misc.c
@@ -749,8 +749,11 @@ retry4:
 	 */
 definitelyEOF:
 	libpq_append_conn_error(conn, "server closed the connection unexpectedly\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 == NULL) ? " null" :
+							(conn->result->resultStatus == PGRES_FATAL_ERROR) ?
+							"" : " abnormally");
 
 	/* Come here if lower-level code already set a suitable errorMessage */
 definitelyFailed:
diff --git a/src/interfaces/libpq/fe-protocol3.c b/src/interfaces/libpq/fe-protocol3.c
index 5613c56b14..03914b97fc 100644
--- 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 = PGRES_FATAL_ERROR;
+				fprintf(stderr, "Got 'E'\n");
 				break;
 			case 'A':			/* notify message */
 				/* handle notify and go back to processing return values */
diff --git a/src/interfaces/libpq/fe-secure-openssl.c b/src/interfaces/libpq/fe-secure-openssl.c
index f1192d28f2..f4c7f51b0a 100644
--- a/src/interfaces/libpq/fe-secure-openssl.c
+++ b/src/interfaces/libpq/fe-secure-openssl.c
@@ -206,8 +206,11 @@ rloop:
 				if (result_errno == EPIPE ||
 					result_errno == ECONNRESET)
 					libpq_append_conn_error(conn, "server closed the connection unexpectedly\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 == NULL) ? " null" :
+											  (conn->result->resultStatus == PGRES_FATAL_ERROR) ?
+											  "" : " abnormally");
 				else
 					libpq_append_conn_error(conn, "SSL SYSCALL error: %s",
 											SOCK_STRERROR(result_errno,
@@ -306,8 +309,11 @@ pgtls_write(PGconn *conn, const void *ptr, size_t len)
 				result_errno = SOCK_ERRNO;
 				if (result_errno == EPIPE || result_errno == ECONNRESET)
 					libpq_append_conn_error(conn, "server closed the connection unexpectedly\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 == NULL) ? " null" :
+											  (conn->result->resultStatus == PGRES_FATAL_ERROR) ?
+											  "" : " abnormally");
 				else
 					libpq_append_conn_error(conn, "SSL SYSCALL error: %s",
 											SOCK_STRERROR(result_errno,
diff --git a/src/interfaces/libpq/fe-secure.c b/src/interfaces/libpq/fe-secure.c
index bd72a87bbb..be93c2c0f9 100644
--- a/src/interfaces/libpq/fe-secure.c
+++ b/src/interfaces/libpq/fe-secure.c
@@ -233,8 +233,11 @@ pqsecure_raw_read(PGconn *conn, void *ptr, size_t len)
 			case EPIPE:
 			case ECONNRESET:
 				libpq_append_conn_error(conn, "server closed the connection unexpectedly\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 == NULL) ? " null" :
+										(conn->result->resultStatus == PGRES_FATAL_ERROR) ?
+										"" : " abnormally");
 				break;
 
 			default:
@@ -395,8 +398,12 @@ retry_masked:
 				/* (strdup failure is OK, we'll cope later) */
 				snprintf(msgbuf, sizeof(msgbuf),
 						 libpq_gettext("server closed the connection unexpectedly\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 == NULL) ? " null" :
+									   (conn->result->resultStatus == PGRES_FATAL_ERROR) ?
+									   "" : " abnormally");
+
 				/* keep newline out of translated string */
 				strlcat(msgbuf, "\n", sizeof(msgbuf));
 				conn->write_err_msg = strdup(msgbuf);

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