v1-0001-Add-errdetail-with-PID-and-UID-about-source-of-te.patch

From 28fe83686c4031eebd1ffad2487aef0101a05295 Mon Sep 17 00:00:00 2001
From: Jakub Wartak <jakub.wartak@enterprisedb.com>
Date: Tue, 17 Feb 2026 12:41:01 +0100
Subject: [PATCH v1] Add errdetail() with PID and UID about source of
 termination signal.

On Linux we can use SA_SIGINFO to fetch additional information about sender
of the signal, which can aid troubleshooting. Sample log:
  FATAL:  terminating connection due to administrator command
  DETAIL:  signal sent by PID 508477, UID 1000.

Author: Jakub Wartak <jakub.wartak@enterprisedb.com>
Reviewed-by:
Discussion:
---
 src/backend/postmaster/bgworker.c |  6 ++++-
 src/backend/replication/syncrep.c | 12 +++++++--
 src/backend/tcop/postgres.c       | 42 +++++++++++++++++++++++++------
 src/backend/utils/init/globals.c  |  2 ++
 src/bin/psql/t/001_basic.pl       |  7 +++---
 src/include/miscadmin.h           |  2 ++
 src/port/pqsignal.c               | 36 +++++++++++++++++++++++---
 7 files changed, 90 insertions(+), 17 deletions(-)

diff --git a/src/backend/postmaster/bgworker.c b/src/backend/postmaster/bgworker.c
index 261ccd3f59..20b1893533 100644
--- a/src/backend/postmaster/bgworker.c
+++ b/src/backend/postmaster/bgworker.c
@@ -729,7 +729,11 @@ bgworker_die(SIGNAL_ARGS)
 	ereport(FATAL,
 			(errcode(ERRCODE_ADMIN_SHUTDOWN),
 			 errmsg("terminating background worker \"%s\" due to administrator command",
-					MyBgworkerEntry->bgw_type)));
+					MyBgworkerEntry->bgw_type),
+			proc_die_sender_pid == 0 ? 0 :
+				errdetail("signal sent by PID %d, UID %d.",
+					proc_die_sender_pid, proc_die_sender_uid)
+			));
 }
 
 /*
diff --git a/src/backend/replication/syncrep.c b/src/backend/replication/syncrep.c
index 7ea6001e9a..339c03fb6a 100644
--- a/src/backend/replication/syncrep.c
+++ b/src/backend/replication/syncrep.c
@@ -302,7 +302,11 @@ SyncRepWaitForLSN(XLogRecPtr lsn, bool commit)
 			ereport(WARNING,
 					(errcode(ERRCODE_ADMIN_SHUTDOWN),
 					 errmsg("canceling the wait for synchronous replication and terminating connection due to administrator command"),
-					 errdetail("The transaction has already committed locally, but might not have been replicated to the standby.")));
+					 errdetail("The transaction has already committed locally, but might not have been replicated to the standby."),
+						proc_die_sender_pid == 0 ? 0 :
+							errdetail("signal sent by PID %d, UID %d.",
+								proc_die_sender_pid, proc_die_sender_uid)
+						));
 			whereToSendOutput = DestNone;
 			SyncRepCancelWait();
 			break;
@@ -319,7 +323,11 @@ SyncRepWaitForLSN(XLogRecPtr lsn, bool commit)
 			QueryCancelPending = false;
 			ereport(WARNING,
 					(errmsg("canceling wait for synchronous replication due to user request"),
-					 errdetail("The transaction has already committed locally, but might not have been replicated to the standby.")));
+					 errdetail("The transaction has already committed locally, but might not have been replicated to the standby."),
+						proc_die_sender_pid == 0 ? 0 :
+							errdetail("signal sent by PID %d, UID %d.",
+								proc_die_sender_pid, proc_die_sender_uid)
+						));
 			SyncRepCancelWait();
 			break;
 		}
diff --git a/src/backend/tcop/postgres.c b/src/backend/tcop/postgres.c
index 21de158adb..115ea965d4 100644
--- a/src/backend/tcop/postgres.c
+++ b/src/backend/tcop/postgres.c
@@ -3357,15 +3357,27 @@ ProcessInterrupts(void)
 		else if (AmAutoVacuumWorkerProcess())
 			ereport(FATAL,
 					(errcode(ERRCODE_ADMIN_SHUTDOWN),
-					 errmsg("terminating autovacuum process due to administrator command")));
+					 errmsg("terminating autovacuum process due to administrator command"),
+					 proc_die_sender_pid == 0 ? 0 :
+						errdetail("signal sent by PID %d, UID %d.",
+							proc_die_sender_pid, proc_die_sender_uid)
+					));
 		else if (IsLogicalWorker())
 			ereport(FATAL,
 					(errcode(ERRCODE_ADMIN_SHUTDOWN),
-					 errmsg("terminating logical replication worker due to administrator command")));
+					 errmsg("terminating logical replication worker due to administrator command"),
+					 proc_die_sender_pid == 0 ? 0 :
+						errdetail("signal sent by PID %d, UID %d.",
+							proc_die_sender_pid, proc_die_sender_uid)
+					));
 		else if (IsLogicalLauncher())
 		{
 			ereport(DEBUG1,
-					(errmsg_internal("logical replication launcher shutting down")));
+					(errmsg_internal("logical replication launcher shutting down"),
+					 proc_die_sender_pid == 0 ? 0 :
+						errdetail("signal sent by PID %d, UID %d.",
+							proc_die_sender_pid, proc_die_sender_uid)
+					));
 
 			/*
 			 * The logical replication launcher can be stopped at any time.
@@ -3376,23 +3388,39 @@ ProcessInterrupts(void)
 		else if (AmWalReceiverProcess())
 			ereport(FATAL,
 					(errcode(ERRCODE_ADMIN_SHUTDOWN),
-					 errmsg("terminating walreceiver process due to administrator command")));
+					 errmsg("terminating walreceiver process due to administrator command"),
+					 proc_die_sender_pid == 0 ? 0 :
+						errdetail("signal sent by PID %d, UID %d.",
+							proc_die_sender_pid, proc_die_sender_uid)
+					));
 		else if (AmBackgroundWorkerProcess())
 			ereport(FATAL,
 					(errcode(ERRCODE_ADMIN_SHUTDOWN),
 					 errmsg("terminating background worker \"%s\" due to administrator command",
-							MyBgworkerEntry->bgw_type)));
+							MyBgworkerEntry->bgw_type),
+					 proc_die_sender_pid == 0 ? 0 :
+						errdetail("signal sent by PID %d, UID %d.",
+							proc_die_sender_pid, proc_die_sender_uid)
+					));
 		else if (AmIoWorkerProcess())
 		{
 			ereport(DEBUG1,
-					(errmsg_internal("io worker shutting down due to administrator command")));
+					(errmsg_internal("io worker shutting down due to administrator command"),
+					 proc_die_sender_pid == 0 ? 0 :
+						errdetail("signal sent by PID %d, UID %d.",
+							proc_die_sender_pid, proc_die_sender_uid)
+					));
 
 			proc_exit(0);
 		}
 		else
 			ereport(FATAL,
 					(errcode(ERRCODE_ADMIN_SHUTDOWN),
-					 errmsg("terminating connection due to administrator command")));
+					 errmsg("terminating connection due to administrator command"),
+					 proc_die_sender_pid == 0 ? 0 :
+						errdetail("signal sent by PID %d, UID %d.",
+							proc_die_sender_pid, proc_die_sender_uid)
+					));
 	}
 
 	if (CheckClientConnectionPending)
diff --git a/src/backend/utils/init/globals.c b/src/backend/utils/init/globals.c
index 36ad708b36..144c8aca1b 100644
--- a/src/backend/utils/init/globals.c
+++ b/src/backend/utils/init/globals.c
@@ -32,6 +32,8 @@ ProtocolVersion FrontendProtocol;
 volatile sig_atomic_t InterruptPending = false;
 volatile sig_atomic_t QueryCancelPending = false;
 volatile sig_atomic_t ProcDiePending = false;
+volatile sig_atomic_t proc_die_sender_pid = 0;
+volatile sig_atomic_t proc_die_sender_uid = 0;
 volatile sig_atomic_t CheckClientConnectionPending = false;
 volatile sig_atomic_t ClientConnectionLost = false;
 volatile sig_atomic_t IdleInTransactionSessionTimeoutPending = false;
diff --git a/src/bin/psql/t/001_basic.pl b/src/bin/psql/t/001_basic.pl
index 6839f27cbe..aa8f819d9d 100644
--- a/src/bin/psql/t/001_basic.pl
+++ b/src/bin/psql/t/001_basic.pl
@@ -142,12 +142,11 @@ my ($ret, $out, $err) = $node->psql('postgres',
 is($ret, 2, 'server crash: psql exit code');
 like($out, qr/before/, 'server crash: output before crash');
 unlike($out, qr/AFTER/, 'server crash: no output after crash');
-is( $err,
-	'psql:<stdin>:2: FATAL:  terminating connection due to administrator command
-psql:<stdin>:2: server closed the connection unexpectedly
+like( $err, qr/psql:<stdin>:2: FATAL:  terminating connection due to administrator command
+(?:DETAIL:  signal sent by PID \d+, UID \d+.\n)?psql:<stdin>:2: server closed the connection unexpectedly
 	This probably means the server terminated abnormally
 	before or while processing the request.
-psql:<stdin>:2: error: connection to server was lost',
+psql:<stdin>:2: error: connection to server was lost/,
 	'server crash: error message');
 
 # test \errverbose
diff --git a/src/include/miscadmin.h b/src/include/miscadmin.h
index f16f35659b..63256eff84 100644
--- a/src/include/miscadmin.h
+++ b/src/include/miscadmin.h
@@ -90,6 +90,8 @@
 extern PGDLLIMPORT volatile sig_atomic_t InterruptPending;
 extern PGDLLIMPORT volatile sig_atomic_t QueryCancelPending;
 extern PGDLLIMPORT volatile sig_atomic_t ProcDiePending;
+extern PGDLLIMPORT volatile sig_atomic_t proc_die_sender_pid;
+extern PGDLLIMPORT volatile sig_atomic_t proc_die_sender_uid;
 extern PGDLLIMPORT volatile sig_atomic_t IdleInTransactionSessionTimeoutPending;
 extern PGDLLIMPORT volatile sig_atomic_t TransactionTimeoutPending;
 extern PGDLLIMPORT volatile sig_atomic_t IdleSessionTimeoutPending;
diff --git a/src/port/pqsignal.c b/src/port/pqsignal.c
index fbdf9341c2..bb632285f4 100644
--- a/src/port/pqsignal.c
+++ b/src/port/pqsignal.c
@@ -82,10 +82,18 @@ static volatile pqsigfunc pqsignal_handlers[PG_NSIG];
  *
  * This wrapper also handles restoring the value of errno.
  */
+#if !defined(FRONTEND) && !defined(WIN32)
+static void
+wrapper_handler(int signo, siginfo_t *info, void *context)
+#else
 static void
 wrapper_handler(SIGNAL_ARGS)
+#endif
 {
 	int			save_errno = errno;
+#if !defined(FRONTEND) && !defined(WIN32)
+	int			postgres_signal_arg = signo;
+#endif
 
 	Assert(postgres_signal_arg > 0);
 	Assert(postgres_signal_arg < PG_NSIG);
@@ -105,6 +113,14 @@ wrapper_handler(SIGNAL_ARGS)
 		raise(postgres_signal_arg);
 		return;
 	}
+
+#ifndef WIN32
+	if (signo == SIGTERM && info)
+	{
+		proc_die_sender_pid = info->si_pid;
+		proc_die_sender_uid = info->si_uid;
+	}
+#endif
 #endif
 
 	(*pqsignal_handlers[postgres_signal_arg]) (postgres_signal_arg);
@@ -125,6 +141,7 @@ pqsignal(int signo, pqsigfunc func)
 #if !(defined(WIN32) && defined(FRONTEND))
 	struct sigaction act;
 #endif
+	bool		use_wrapper = false;
 
 	Assert(signo > 0);
 	Assert(signo < PG_NSIG);
@@ -132,13 +149,26 @@ pqsignal(int signo, pqsigfunc func)
 	if (func != SIG_IGN && func != SIG_DFL)
 	{
 		pqsignal_handlers[signo] = func;	/* assumed atomic */
-		func = wrapper_handler;
+		use_wrapper = true;
 	}
 
 #if !(defined(WIN32) && defined(FRONTEND))
-	act.sa_handler = func;
 	sigemptyset(&act.sa_mask);
 	act.sa_flags = SA_RESTART;
+#if !defined(FRONTEND) && !defined(WIN32)
+	if (use_wrapper)
+	{
+		act.sa_sigaction = wrapper_handler;
+		act.sa_flags |= SA_SIGINFO;
+	}
+	else
+	{
+		act.sa_handler = func;
+	}
+#else
+	act.sa_handler = use_wrapper ? wrapper_handler : func;
+#endif
+
 #ifdef SA_NOCLDSTOP
 	if (signo == SIGCHLD)
 		act.sa_flags |= SA_NOCLDSTOP;
@@ -147,7 +177,7 @@ pqsignal(int signo, pqsigfunc func)
 		Assert(false);			/* probably indicates coding error */
 #else
 	/* Forward to Windows native signal system. */
-	if (signal(signo, func) == SIG_ERR)
+	if (signal(signo, use_wrapper ? wrapper_handler : func) == SIG_ERR)
 		Assert(false);			/* probably indicates coding error */
 #endif
 }
-- 
2.43.0