From 7cd875d4b35ec7c7503c194b01a7d15e52fe0b8b Mon Sep 17 00:00:00 2001
From: Hari Babu <kommi.haribabu@gmail.com>
Date: Thu, 21 Dec 2017 16:59:25 +1100
Subject: [PATCH] pg_stat_wal_receiver to display connected host

With the support of multi host connection string support
in PostgreSQL, it is possible for the user to specify the
multi host connection string in recovery.conf to avoid
breakdown of streaming replication.

The pg_stat_wal_receiver view is enhanced to support display
of remote host information from which the replication is
streaming currently.
---
 doc/src/sgml/monitoring.sgml                       | 15 +++++++++
 src/backend/catalog/system_views.sql               |  3 ++
 .../libpqwalreceiver/libpqwalreceiver.c            |  8 +++--
 src/backend/replication/walreceiver.c              | 38 ++++++++++++++++++++--
 src/include/catalog/pg_proc.h                      |  2 +-
 src/include/replication/walreceiver.h              | 12 +++++--
 src/interfaces/libpq/exports.txt                   |  1 +
 src/interfaces/libpq/fe-connect.c                  | 17 ++++++++++
 src/interfaces/libpq/libpq-fe.h                    |  1 +
 src/test/regress/expected/rules.out                |  5 ++-
 10 files changed, 92 insertions(+), 10 deletions(-)

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 8a9793644f..fbdecdaff3 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -2022,6 +2022,21 @@ 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>remote_hostname</structfield></entry>
+     <entry><type>text</type></entry>
+     <entry>Host name of the PostgreSQL instance this WAL receiver is connected to</entry>
+    </row>
+    <row>
+     <entry><structfield>remote_hostaddr</structfield></entry>
+     <entry><type>text</type></entry>
+     <entry>Host address of the PostgreSQL instance this WAL receiver is connected to</entry>
+    </row>
+    <row>
+     <entry><structfield>remote_port</structfield></entry>
+     <entry><type>integer</type></entry>
+     <entry>port number of the PostgreSQL instance this WAL receiver is connected to</entry>
+    </row>
     <row>
      <entry><structfield>conninfo</structfield></entry>
      <entry><type>text</type></entry>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 394aea8e0f..6f658801ea 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -750,6 +750,9 @@ CREATE VIEW pg_stat_wal_receiver AS
             s.latest_end_lsn,
             s.latest_end_time,
             s.slot_name,
+            s.remote_hostname,
+            s.remote_hostaddr,
+            s.remote_port,
             s.conninfo
     FROM pg_stat_get_wal_receiver() s
     WHERE s.pid IS NOT NULL;
diff --git a/src/backend/replication/libpqwalreceiver/libpqwalreceiver.c b/src/backend/replication/libpqwalreceiver/libpqwalreceiver.c
index 3957bd37fb..c43d815fea 100644
--- a/src/backend/replication/libpqwalreceiver/libpqwalreceiver.c
+++ b/src/backend/replication/libpqwalreceiver/libpqwalreceiver.c
@@ -52,7 +52,8 @@ static WalReceiverConn *libpqrcv_connect(const char *conninfo,
 				 bool logical, const char *appname,
 				 char **err);
 static void libpqrcv_check_conninfo(const char *conninfo);
-static char *libpqrcv_get_conninfo(WalReceiverConn *conn);
+static char *libpqrcv_get_conninfo(WalReceiverConn *conn, char **host,
+		  char **hostaddr, int *port);
 static char *libpqrcv_identify_system(WalReceiverConn *conn,
 						 TimeLineID *primary_tli,
 						 int *server_version);
@@ -238,7 +239,8 @@ libpqrcv_check_conninfo(const char *conninfo)
  * are obfuscated.
  */
 static char *
-libpqrcv_get_conninfo(WalReceiverConn *conn)
+libpqrcv_get_conninfo(WalReceiverConn *conn, char **host,
+					  char **hostaddr, int *port)
 {
 	PQconninfoOption *conn_opts;
 	PQconninfoOption *conn_opt;
@@ -277,6 +279,8 @@ libpqrcv_get_conninfo(WalReceiverConn *conn)
 
 	PQconninfoFree(conn_opts);
 
+	PQconnectedhostinfo(conn->streamConn, host, hostaddr, port);
+
 	retval = PQExpBufferDataBroken(buf) ? NULL : pstrdup(buf.data);
 	termPQExpBuffer(&buf);
 	return retval;
diff --git a/src/backend/replication/walreceiver.c b/src/backend/replication/walreceiver.c
index fe4e085938..c2ce4e4f09 100644
--- a/src/backend/replication/walreceiver.c
+++ b/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 +200,9 @@ WalReceiverMain(void)
 	TimestampTz now;
 	bool		ping_sent;
 	char	   *err;
+	char	   *host = NULL;
+	char	   *hostaddr = NULL;
+	int			port = 0;
 
 	/*
 	 * WalRcv should be set up already (if we are a backend, we inherit this
@@ -310,11 +314,21 @@ WalReceiverMain(void)
 	 * Save user-visible connection string.  This clobbers the original
 	 * conninfo, for security.
 	 */
-	tmp_conninfo = walrcv_get_conninfo(wrconn);
+	tmp_conninfo = walrcv_get_conninfo(wrconn, &host, &hostaddr, &port);
 	SpinLockAcquire(&walrcv->mutex);
 	memset(walrcv->conninfo, 0, MAXCONNINFO);
 	if (tmp_conninfo)
 		strlcpy((char *) walrcv->conninfo, tmp_conninfo, MAXCONNINFO);
+
+	memset(walrcv->host, 0, NAMEDATALEN);
+	if (host)
+		strlcpy((char *) walrcv->host, host, NAMEDATALEN);
+
+	memset(walrcv->hostaddr, 0, NAMEDATALEN);
+	if (hostaddr)
+		strlcpy((char *) walrcv->hostaddr, hostaddr, NAMEDATALEN);
+
+	walrcv->port = port;
 	walrcv->ready_to_display = true;
 	SpinLockRelease(&walrcv->mutex);
 
@@ -1402,6 +1416,9 @@ pg_stat_get_wal_receiver(PG_FUNCTION_ARGS)
 	TimestampTz last_receipt_time;
 	XLogRecPtr	latest_end_lsn;
 	TimestampTz latest_end_time;
+	char		host[NI_MAXHOST];
+	char		hostaddr[NI_MAXHOST];
+	int			port = 0;
 	char		slotname[NAMEDATALEN];
 	char		conninfo[MAXCONNINFO];
 
@@ -1419,6 +1436,9 @@ 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(host, (char *) WalRcv->host, sizeof(host));
+	strlcpy(hostaddr, (char *) WalRcv->hostaddr, sizeof(hostaddr));
+	port = WalRcv->port;
 	strlcpy(conninfo, (char *) WalRcv->conninfo, sizeof(conninfo));
 	SpinLockRelease(&WalRcv->mutex);
 
@@ -1481,10 +1501,22 @@ pg_stat_get_wal_receiver(PG_FUNCTION_ARGS)
 			nulls[10] = true;
 		else
 			values[10] = CStringGetTextDatum(slotname);
-		if (*conninfo == '\0')
+		if (*host == '\0')
 			nulls[11] = true;
 		else
-			values[11] = CStringGetTextDatum(conninfo);
+			values[11] = CStringGetTextDatum(host);
+		if (*hostaddr == '\0')
+			nulls[12] = true;
+		else
+			values[12] = CStringGetTextDatum(hostaddr);
+		if (port == 0)
+			nulls[13] = true;
+		else
+			values[13] = Int32GetDatum(port);
+		if (*conninfo == '\0')
+			nulls[14] = true;
+		else
+			values[14] = CStringGetTextDatum(conninfo);
 	}
 
 	/* Returns the record as Datum */
diff --git a/src/include/catalog/pg_proc.h b/src/include/catalog/pg_proc.h
index 830bab37ea..4d6b842f89 100644
--- a/src/include/catalog/pg_proc.h
+++ b/src/include/catalog/pg_proc.h
@@ -2883,7 +2883,7 @@ 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 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 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 f s r 0 0 2249 "" "{23,25,3220,23,3220,23,1184,1184,3220,1184,25,25,25,23,25}" "{o,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,remote_hostname,remote_hostaddr,remote_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 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");
diff --git a/src/include/replication/walreceiver.h b/src/include/replication/walreceiver.h
index e58fc49c68..74ae054468 100644
--- a/src/include/replication/walreceiver.h
+++ b/src/include/replication/walreceiver.h
@@ -107,6 +107,9 @@ typedef struct
 	 * clobbered to hide security-sensitive fields.
 	 */
 	char		conninfo[MAXCONNINFO];
+	char		host[NI_MAXHOST];
+	char		hostaddr[NI_MAXHOST];
+	int			port;
 
 	/*
 	 * replication slot name; is also used for walreceiver to connect with the
@@ -196,7 +199,10 @@ typedef WalReceiverConn *(*walrcv_connect_fn) (const char *conninfo, bool logica
 											   const char *appname,
 											   char **err);
 typedef void (*walrcv_check_conninfo_fn) (const char *conninfo);
-typedef char *(*walrcv_get_conninfo_fn) (WalReceiverConn *conn);
+typedef char *(*walrcv_get_conninfo_fn) (WalReceiverConn *conn,
+										 char **host,
+										 char **hostaddr,
+										 int *port);
 typedef char *(*walrcv_identify_system_fn) (WalReceiverConn *conn,
 											TimeLineID *primary_tli,
 											int *server_version);
@@ -244,8 +250,8 @@ extern PGDLLIMPORT WalReceiverFunctionsType *WalReceiverFunctions;
 	WalReceiverFunctions->walrcv_connect(conninfo, logical, appname, err)
 #define walrcv_check_conninfo(conninfo) \
 	WalReceiverFunctions->walrcv_check_conninfo(conninfo)
-#define walrcv_get_conninfo(conn) \
-	WalReceiverFunctions->walrcv_get_conninfo(conn)
+#define walrcv_get_conninfo(conn, host, hostaddr, port) \
+	WalReceiverFunctions->walrcv_get_conninfo(conn, host, hostaddr, 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) \
diff --git a/src/interfaces/libpq/exports.txt b/src/interfaces/libpq/exports.txt
index d6a38d0df8..97ad8c9594 100644
--- a/src/interfaces/libpq/exports.txt
+++ b/src/interfaces/libpq/exports.txt
@@ -172,3 +172,4 @@ PQsslAttribute            169
 PQsetErrorContextVisibility 170
 PQresultVerboseErrorMessage 171
 PQencryptPasswordConn     172
+PQconnectedhostinfo			173
\ No newline at end of file
diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c
index 68fb9a124a..58fcc7067c 100644
--- a/src/interfaces/libpq/fe-connect.c
+++ b/src/interfaces/libpq/fe-connect.c
@@ -6032,6 +6032,23 @@ PQhost(const PGconn *conn)
 	}
 }
 
+/* Provides connected host info details */
+void
+PQconnectedhostinfo(const PGconn *conn, char **host, char **hostaddr, int *port)
+{
+	if (!conn || !conn->connhost)
+		return;
+
+	if (conn->connhost[conn->whichhost].host)
+		*host = pstrdup(conn->connhost[conn->whichhost].host);
+
+	if (conn->connhost[conn->whichhost].hostaddr)
+		*hostaddr = pstrdup(conn->connhost[conn->whichhost].hostaddr);
+
+	if (conn->connhost[conn->whichhost].port)
+		*port = atoi(conn->connhost[conn->whichhost].port);
+}
+
 char *
 PQport(const PGconn *conn)
 {
diff --git a/src/interfaces/libpq/libpq-fe.h b/src/interfaces/libpq/libpq-fe.h
index 1d915e7915..c85ffc6a7e 100644
--- a/src/interfaces/libpq/libpq-fe.h
+++ b/src/interfaces/libpq/libpq-fe.h
@@ -312,6 +312,7 @@ extern char *PQdb(const PGconn *conn);
 extern char *PQuser(const PGconn *conn);
 extern char *PQpass(const PGconn *conn);
 extern char *PQhost(const PGconn *conn);
+extern void PQconnectedhostinfo(const PGconn *conn, char **host, char **hostaddr, int *port);
 extern char *PQport(const PGconn *conn);
 extern char *PQtty(const PGconn *conn);
 extern char *PQoptions(const PGconn *conn);
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index f1c1b44d6f..f216bd33de 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1970,8 +1970,11 @@ pg_stat_wal_receiver| SELECT s.pid,
     s.latest_end_lsn,
     s.latest_end_time,
     s.slot_name,
+    s.remote_hostname,
+    s.remote_hostaddr,
+    s.remote_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, remote_hostname, remote_hostaddr, remote_port, conninfo)
   WHERE (s.pid IS NOT NULL);
 pg_stat_xact_all_tables| SELECT c.oid AS relid,
     n.nspname AS schemaname,
-- 
2.15.0.windows.1

