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

doc/src/sgml/monitoring.sgml

@@ -2031,6 +2031,25 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
      <entry><type>text</type></entry>
      <entry>Replication slot name used by this WAL receiver</entry>
     </row>
+    <row>
+     <entry><structfield>sender_host</structfield></entry>
+     <entry><type>text</type></entry>
+     <entry>
+      Host of the <productname>PostgreSQL</productname> instance
+      this WAL receiver is connected to. This can be a host name,
+      an IP address, or a directory path if the connection is via
+      Unix socket.  (The path case can be distinguished because it
+      will always be an absolute path, beginning with <literal>/</literal>.)
+     </entry>
+    </row>
+    <row>
+     <entry><structfield>sender_port</structfield></entry>
+     <entry><type>integer</type></entry>
+     <entry>
+      Port number of the <productname>PostgreSQL</productname> instance
+      this WAL receiver is connected to.
+     </entry>
+    </row>
     <row>
      <entry><structfield>conninfo</structfield></entry>
      <entry><type>text</type></entry>

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 */

src/include/catalog/catversion.h

@@ -53,6 +53,6 @@
  */
 
 /*							yyyymmddN */
-#define CATALOG_VERSION_NO	201803291
+#define CATALOG_VERSION_NO	201803311
 
 #endif

src/include/catalog/pg_proc.h

@@ -2919,7 +2919,7 @@ DATA(insert OID = 3318 (  pg_stat_get_progress_info			  PGNSP PGUID 12 1 100 0 0
 DESCR("statistics: information about progress of backends running maintenance command");
 DATA(insert OID = 3099 (  pg_stat_get_wal_senders	PGNSP PGUID 12 1 10 0 0 f f f f t s r 0 0 2249 "" "{23,25,3220,3220,3220,3220,1186,1186,1186,23,25}" "{o,o,o,o,o,o,o,o,o,o,o}" "{pid,state,sent_lsn,write_lsn,flush_lsn,replay_lsn,write_lag,flush_lag,replay_lag,sync_priority,sync_state}" _null_ _null_ pg_stat_get_wal_senders _null_ _null_ _null_ ));
 DESCR("statistics: information about currently active replication");
-DATA(insert OID = 3317 (  pg_stat_get_wal_receiver	PGNSP PGUID 12 1 0 0 0 f f f f f s r 0 0 2249 "" "{23,25,3220,23,3220,23,1184,1184,3220,1184,25,25}" "{o,o,o,o,o,o,o,o,o,o,o,o}" "{pid,status,receive_start_lsn,receive_start_tli,received_lsn,received_tli,last_msg_send_time,last_msg_receipt_time,latest_end_lsn,latest_end_time,slot_name,conninfo}" _null_ _null_ pg_stat_get_wal_receiver _null_ _null_ _null_ ));
+DATA(insert OID = 3317 (  pg_stat_get_wal_receiver	PGNSP PGUID 12 1 0 0 0 f f f f f s r 0 0 2249 "" "{23,25,3220,23,3220,23,1184,1184,3220,1184,25,25,23,25}" "{o,o,o,o,o,o,o,o,o,o,o,o,o,o}" "{pid,status,receive_start_lsn,receive_start_tli,received_lsn,received_tli,last_msg_send_time,last_msg_receipt_time,latest_end_lsn,latest_end_time,slot_name,sender_host,sender_port,conninfo}" _null_ _null_ pg_stat_get_wal_receiver _null_ _null_ _null_ ));
 DESCR("statistics: information about WAL receiver");
 DATA(insert OID = 6118 (  pg_stat_get_subscription	PGNSP PGUID 12 1 0 0 0 f f f f f s r 1 0 2249 "26" "{26,26,26,23,3220,1184,1184,3220,1184}" "{i,o,o,o,o,o,o,o,o}" "{subid,subid,relid,pid,received_lsn,last_msg_send_time,last_msg_receipt_time,latest_end_lsn,latest_end_time}" _null_ _null_ pg_stat_get_subscription _null_ _null_ _null_ ));
 DESCR("statistics: information about subscription");

src/include/replication/walreceiver.h

@@ -108,6 +108,13 @@ typedef struct
 	 */
 	char		conninfo[MAXCONNINFO];
 
+	/*
+	 * Host name (this can be a host name, an IP address, or a directory
+	 * path) and port number of the active replication connection.
+	 */
+	char		sender_host[NI_MAXHOST];
+	int			sender_port;
+
 	/*
 	 * replication slot name; is also used for walreceiver to connect with the
 	 * primary
@@ -197,6 +204,9 @@ typedef WalReceiverConn *(*walrcv_connect_fn) (const char *conninfo, bool logica
 											   char **err);
 typedef void (*walrcv_check_conninfo_fn) (const char *conninfo);
 typedef char *(*walrcv_get_conninfo_fn) (WalReceiverConn *conn);
+typedef void (*walrcv_get_senderinfo_fn) (WalReceiverConn *conn,
+										 char **sender_host,
+										 int *sender_port);
 typedef char *(*walrcv_identify_system_fn) (WalReceiverConn *conn,
 											TimeLineID *primary_tli,
 											int *server_version);
@@ -227,6 +237,7 @@ typedef struct WalReceiverFunctionsType
 	walrcv_connect_fn walrcv_connect;
 	walrcv_check_conninfo_fn walrcv_check_conninfo;
 	walrcv_get_conninfo_fn walrcv_get_conninfo;
+	walrcv_get_senderinfo_fn walrcv_get_senderinfo;
 	walrcv_identify_system_fn walrcv_identify_system;
 	walrcv_readtimelinehistoryfile_fn walrcv_readtimelinehistoryfile;
 	walrcv_startstreaming_fn walrcv_startstreaming;
@@ -246,6 +257,8 @@ extern PGDLLIMPORT WalReceiverFunctionsType *WalReceiverFunctions;
 	WalReceiverFunctions->walrcv_check_conninfo(conninfo)
 #define walrcv_get_conninfo(conn) \
 	WalReceiverFunctions->walrcv_get_conninfo(conn)
+#define walrcv_get_senderinfo(conn, sender_host, sender_port) \
+	WalReceiverFunctions->walrcv_get_senderinfo(conn, sender_host, sender_port)
 #define walrcv_identify_system(conn, primary_tli, server_version) \
 	WalReceiverFunctions->walrcv_identify_system(conn, primary_tli, server_version)
 #define walrcv_readtimelinehistoryfile(conn, tli, filename, content, size) \

src/test/regress/expected/rules.out

@@ -1972,8 +1972,10 @@ pg_stat_wal_receiver| SELECT s.pid,
     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(pid, status, receive_start_lsn, receive_start_tli, received_lsn, received_tli, last_msg_send_time, last_msg_receipt_time, latest_end_lsn, latest_end_time, slot_name, conninfo)
+   FROM pg_stat_get_wal_receiver() s(pid, status, receive_start_lsn, receive_start_tli, received_lsn, received_tli, last_msg_send_time, last_msg_receipt_time, latest_end_lsn, latest_end_time, slot_name, sender_host, sender_port, conninfo)
   WHERE (s.pid IS NOT NULL);
 pg_stat_xact_all_tables| SELECT c.oid AS relid,
     n.nspname AS schemaname,