v5-0001-Add-custom-PQsetNoticeReceiver-handlers-for-repli.patch

From 8a0d5392f482572ebd57a6eae30c715c81b31963 Mon Sep 17 00:00:00 2001
From: Vignesh C <vignesh21@gmail.com>
Date: Wed, 16 Jul 2025 15:26:12 +0530
Subject: [PATCH v5 1/3] Add custom PQsetNoticeReceiver handlers for
 replication connection

This patch introduces a custom notice receiver for replication
connections. The notice receiver captures messages and routes
them through ereport(), making them visible in local logs with
a prefix making it easy for diagnosis.
---
 .../libpqwalreceiver/libpqwalreceiver.c       | 30 +++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/src/backend/replication/libpqwalreceiver/libpqwalreceiver.c b/src/backend/replication/libpqwalreceiver/libpqwalreceiver.c
index f7b5d093681..7d1031139ac 100644
--- a/src/backend/replication/libpqwalreceiver/libpqwalreceiver.c
+++ b/src/backend/replication/libpqwalreceiver/libpqwalreceiver.c
@@ -114,6 +114,7 @@ static WalReceiverFunctionsType PQWalReceiverFunctions = {
 };
 
 /* Prototypes for private functions */
+static void notice_receiver(void *arg, const PGresult *result);
 static char *stringlist_to_identifierstr(PGconn *conn, List *strings);
 
 /*
@@ -232,6 +233,13 @@ libpqrcv_connect(const char *conninfo, bool replication, bool logical,
 				 errhint("Target server's authentication method must be changed, or set password_required=false in the subscription parameters.")));
 	}
 
+	/*
+	 * Set a custom notice receiver so that NOTICEs, WARNINGs, and similar
+	 * messages from the replication connection are reported via ereport(),
+	 * instead of being printed to stderr.
+	 */
+	PQsetNoticeReceiver(conn->streamConn, notice_receiver, NULL);
+
 	/*
 	 * Set always-secure search path for the cases where the connection is
 	 * used to run SQL queries, so malicious users can't get control.
@@ -1195,6 +1203,28 @@ libpqrcv_exec(WalReceiverConn *conn, const char *query,
 	return walres;
 }
 
+/*
+ * Custom notice receiver for replication connection.
+ */
+static void
+notice_receiver(void *arg, const PGresult *result)
+{
+	char	   *message;
+	int			len;
+
+	/*
+	 * Trim the trailing newline from the message text passed to the notice
+	 * receiver, as it always includes one, to produce cleaner log output.
+	 */
+	message = PQresultErrorMessage(result);
+	len = strlen(message);
+	if (len > 0 && message[len - 1] == '\n')
+		len--;
+
+	ereport(LOG,
+			errmsg("received message via replication: %.*s", len, message));
+}
+
 /*
  * Given a List of strings, return it as single comma separated
  * string, quoting identifiers as needed.
-- 
2.43.0