Enhance pg_stat_wal_receiver view to display host and port of sender server.

Previously there was no way in the standby side to find out the host and port
of the sender server that the walreceiver was currently connected to when
multiple hosts and ports were specified in primary_conninfo. For that purpose,
this patch adds sender_host and sender_port columns into pg_stat_wal_receiver
view. They report the host and port that the active replication connection
currently uses.

Bump catalog version.

Author: Haribabu Kommi
Reviewed-by: Michael Paquier and me

Discussion: https://postgr.es/m/CAJrrPGcV_aq8=cdqkFhVDJKEnDQ70yRTTdY9RODzMnXNrCz2Ow@mail.gmail.com

src/backend/catalog/system_views.sql

@@ -752,6 +752,8 @@ CREATE VIEW pg_stat_wal_receiver AS
             s.latest_end_lsn,
             s.latest_end_time,
             s.slot_name,
+            s.sender_host,
+            s.sender_port,
             s.conninfo
     FROM pg_stat_get_wal_receiver() s
     WHERE s.pid IS NOT NULL;

src/backend/replication/libpqwalreceiver/libpqwalreceiver.c

@@ -53,6 +53,8 @@ static WalReceiverConn *libpqrcv_connect(const char *conninfo,
 				 char **err);
 static void libpqrcv_check_conninfo(const char *conninfo);
 static char *libpqrcv_get_conninfo(WalReceiverConn *conn);
+static void libpqrcv_get_senderinfo(WalReceiverConn *conn,
+					char **sender_host, int *sender_port);
 static char *libpqrcv_identify_system(WalReceiverConn *conn,
 						 TimeLineID *primary_tli,
 						 int *server_version);
@@ -82,6 +84,7 @@ static WalReceiverFunctionsType PQWalReceiverFunctions = {
 	libpqrcv_connect,
 	libpqrcv_check_conninfo,
 	libpqrcv_get_conninfo,
+	libpqrcv_get_senderinfo,
 	libpqrcv_identify_system,
 	libpqrcv_readtimelinehistoryfile,
 	libpqrcv_startstreaming,
@@ -282,6 +285,29 @@ libpqrcv_get_conninfo(WalReceiverConn *conn)
 	return retval;
 }
 
+/*
+ * Provides information of sender this WAL receiver is connected to.
+ */
+static void
+libpqrcv_get_senderinfo(WalReceiverConn *conn, char **sender_host,
+					  int *sender_port)
+{
+	char *ret = NULL;
+
+	*sender_host = NULL;
+	*sender_port = 0;
+
+	Assert(conn->streamConn != NULL);
+
+	ret = PQhost(conn->streamConn);
+	if (ret && strlen(ret) != 0)
+		*sender_host = pstrdup(ret);
+
+	ret = PQport(conn->streamConn);
+	if (ret && strlen(ret) != 0)
+		*sender_port = atoi(ret);
+}
+
 /*
  * Check that primary's system identifier matches ours, and fetch the current
  * timeline ID of the primary.

src/backend/replication/walreceiver.c

@@ -52,6 +52,7 @@
 #include "access/xlog_internal.h"
 #include "catalog/pg_authid.h"
 #include "catalog/pg_type.h"
+#include "common/ip.h"
 #include "funcapi.h"
 #include "libpq/pqformat.h"
 #include "libpq/pqsignal.h"
@@ -199,6 +200,8 @@ WalReceiverMain(void)
 	TimestampTz now;
 	bool		ping_sent;
 	char	   *err;
+	char	   *sender_host = NULL;
+	int			sender_port = 0;
 
 	/*
 	 * WalRcv should be set up already (if we are a backend, we inherit this
@@ -308,19 +311,30 @@ WalReceiverMain(void)
 
 	/*
 	 * Save user-visible connection string.  This clobbers the original
-	 * conninfo, for security.
+	 * conninfo, for security. Also save host and port of the sender server
+	 * this walreceiver is connected to.
 	 */
 	tmp_conninfo = walrcv_get_conninfo(wrconn);
+	walrcv_get_senderinfo(wrconn, &sender_host, &sender_port);
 	SpinLockAcquire(&walrcv->mutex);
 	memset(walrcv->conninfo, 0, MAXCONNINFO);
 	if (tmp_conninfo)
 		strlcpy((char *) walrcv->conninfo, tmp_conninfo, MAXCONNINFO);
+
+	memset(walrcv->sender_host, 0, NI_MAXHOST);
+	if (sender_host)
+		strlcpy((char *) walrcv->sender_host, sender_host, NI_MAXHOST);
+
+	walrcv->sender_port = sender_port;
 	walrcv->ready_to_display = true;
 	SpinLockRelease(&walrcv->mutex);
 
 	if (tmp_conninfo)
 		pfree(tmp_conninfo);
 
+	if (sender_host)
+		pfree(sender_host);
+
 	first_stream = true;
 	for (;;)
 	{
@@ -1402,6 +1416,8 @@ pg_stat_get_wal_receiver(PG_FUNCTION_ARGS)
 	TimestampTz last_receipt_time;
 	XLogRecPtr	latest_end_lsn;
 	TimestampTz latest_end_time;
+	char		sender_host[NI_MAXHOST];
+	int			sender_port = 0;
 	char		slotname[NAMEDATALEN];
 	char		conninfo[MAXCONNINFO];
 
@@ -1419,6 +1435,8 @@ pg_stat_get_wal_receiver(PG_FUNCTION_ARGS)
 	latest_end_lsn = WalRcv->latestWalEnd;
 	latest_end_time = WalRcv->latestWalEndTime;
 	strlcpy(slotname, (char *) WalRcv->slotname, sizeof(slotname));
+	strlcpy(sender_host, (char *) WalRcv->sender_host, sizeof(sender_host));
+	sender_port = WalRcv->sender_port;
 	strlcpy(conninfo, (char *) WalRcv->conninfo, sizeof(conninfo));
 	SpinLockRelease(&WalRcv->mutex);
 
@@ -1482,10 +1500,18 @@ pg_stat_get_wal_receiver(PG_FUNCTION_ARGS)
 			nulls[10] = true;
 		else
 			values[10] = CStringGetTextDatum(slotname);
-		if (*conninfo == '\0')
+		if (*sender_host == '\0')
 			nulls[11] = true;
 		else
-			values[11] = CStringGetTextDatum(conninfo);
+			values[11] = CStringGetTextDatum(sender_host);
+		if (sender_port == 0)
+			nulls[12] = true;
+		else
+			values[12] = Int32GetDatum(sender_port);
+		if (*conninfo == '\0')
+			nulls[13] = true;
+		else
+			values[13] = CStringGetTextDatum(conninfo);
 	}
 
 	/* Returns the record as Datum */