repmgrd: store upstream node ID in shared memory

dbutils.c

@@ -1940,6 +1940,31 @@ get_wal_receiver_pid(PGconn *conn)
 	return wal_receiver_pid;
 }
 
+
+int
+repmgrd_get_upstream_node_id(PGconn *conn)
+{
+	PGresult   *res = NULL;
+	int upstream_node_id = UNKNOWN_NODE_ID;
+
+	const char *sqlquery = "SELECT repmgr.get_upstream_node_id()";
+
+	res = PQexec(conn, sqlquery);
+
+	if (PQresultStatus(res) != PGRES_TUPLES_OK)
+	{
+		log_db_error(conn, sqlquery, _("repmgrd_get_upstream_node_id(): unable to execute query"));
+	}
+	else if (!PQgetisnull(res, 0, 0))
+	{
+		upstream_node_id = atoi(PQgetvalue(res, 0, 0));
+	}
+
+	PQclear(res);
+
+	return upstream_node_id;
+}
+
 /* ================ */
 /* result functions */
 /* ================ */
@@ -5234,15 +5259,16 @@ is_downstream_node_attached(PGconn *conn, char *node_name)
 
 
 void
-set_upstream_last_seen(PGconn *conn)
+set_upstream_last_seen(PGconn *conn, int upstream_node_id)
 {
 	PQExpBufferData query;
 	PGresult   *res = NULL;
 
 	initPQExpBuffer(&query);
 
-	appendPQExpBufferStr(&query,
-						 "SELECT repmgr.set_upstream_last_seen()");
+	appendPQExpBuffer(&query,
+					  "SELECT repmgr.set_upstream_last_seen(%i)",
+					  upstream_node_id);
 
 	res = PQexec(conn, query.data);
 

dbutils.h

@@ -440,6 +440,7 @@ bool		repmgrd_is_running(PGconn *conn);
 bool		repmgrd_is_paused(PGconn *conn);
 bool		repmgrd_pause(PGconn *conn, bool pause);
 pid_t		get_wal_receiver_pid(PGconn *conn);
+int			repmgrd_get_upstream_node_id(PGconn *conn);
 
 /* extension functions */
 ExtensionStatus get_repmgr_extension_status(PGconn *conn, t_extension_versions *extversions);
@@ -560,8 +561,9 @@ bool		get_replication_info(PGconn *conn, t_server_type node_type, ReplInfo *repl
 int			get_replication_lag_seconds(PGconn *conn);
 void		get_node_replication_stats(PGconn *conn, t_node_info *node_info);
 bool		is_downstream_node_attached(PGconn *conn, char *node_name);
-void		set_upstream_last_seen(PGconn *conn);
+void		set_upstream_last_seen(PGconn *conn, int upstream_node_id);
 int			get_upstream_last_seen(PGconn *conn, t_server_type node_type);
+
 bool		is_wal_replay_paused(PGconn *conn, bool check_pending_wal);
 
 /* BDR functions */

repmgr--4.3--4.4.sql

@@ -1,2 +1,14 @@
 -- complain if script is sourced in psql, rather than via CREATE EXTENSION
 \echo Use "CREATE EXTENSION repmgr" to load this file. \quit
+
+DROP FUNCTION set_upstream_last_seen();
+
+CREATE FUNCTION set_upstream_last_seen(INT)
+  RETURNS VOID
+  AS 'MODULE_PATHNAME', 'set_upstream_last_seen'
+  LANGUAGE C STRICT;
+
+CREATE FUNCTION get_upstream_node_id()
+  RETURNS INT
+  AS 'MODULE_PATHNAME', 'get_upstream_node_id'
+  LANGUAGE C STRICT;

repmgr--4.4.sql

@@ -118,7 +118,7 @@ CREATE FUNCTION standby_get_last_updated()
   AS 'MODULE_PATHNAME', 'standby_get_last_updated'
   LANGUAGE C STRICT;
 
-CREATE FUNCTION set_upstream_last_seen()
+CREATE FUNCTION set_upstream_last_seen(INT)
   RETURNS VOID
   AS 'MODULE_PATHNAME', 'set_upstream_last_seen'
   LANGUAGE C STRICT;
@@ -128,6 +128,11 @@ CREATE FUNCTION get_upstream_last_seen()
   AS 'MODULE_PATHNAME', 'get_upstream_last_seen'
   LANGUAGE C STRICT;
 
+CREATE FUNCTION get_upstream_node_id()
+  RETURNS INT
+  AS 'MODULE_PATHNAME', 'get_upstream_node_id'
+  LANGUAGE C STRICT;
+
 
 /* failover functions */
 

repmgr.c

@@ -78,6 +78,7 @@ typedef struct repmgrdSharedState
 	char		repmgrd_pidfile[MAXPGPATH];
 	bool		repmgrd_paused;
 	/* streaming failover */
+	int			upstream_node_id;
 	TimestampTz upstream_last_seen;
 	NodeVotingStatus voting_status;
 	int			current_electoral_term;
@@ -115,6 +116,9 @@ PG_FUNCTION_INFO_V1(set_upstream_last_seen);
 Datum		get_upstream_last_seen(PG_FUNCTION_ARGS);
 PG_FUNCTION_INFO_V1(get_upstream_last_seen);
 
+Datum		get_upstream_node_id(PG_FUNCTION_ARGS);
+PG_FUNCTION_INFO_V1(get_upstream_node_id);
+
 Datum		notify_follow_primary(PG_FUNCTION_ARGS);
 PG_FUNCTION_INFO_V1(notify_follow_primary);
 
@@ -228,6 +232,7 @@ repmgr_shmem_startup(void)
 		memset(shared_state->repmgrd_pidfile, 0, MAXPGPATH);
 		shared_state->repmgrd_paused = false;
 		shared_state->current_electoral_term = 0;
+		shared_state->upstream_node_id = UNKNOWN_NODE_ID;
 		/* arbitrary "magic" date to indicate this field hasn't been updated */
 		shared_state->upstream_last_seen = POSTGRES_EPOCH_JDATE;
 		shared_state->voting_status = VS_NO_VOTE;
@@ -368,13 +373,20 @@ standby_get_last_updated(PG_FUNCTION_ARGS)
 Datum
 set_upstream_last_seen(PG_FUNCTION_ARGS)
 {
+	int			upstream_node_id = UNKNOWN_NODE_ID;
+
 	if (!shared_state)
 		PG_RETURN_VOID();
 
+	if (PG_ARGISNULL(0))
+		PG_RETURN_NULL();
+
+	upstream_node_id = PG_GETARG_INT32(0);
+
 	LWLockAcquire(shared_state->lock, LW_EXCLUSIVE);
 
 	shared_state->upstream_last_seen = GetCurrentTimestamp();
-
+	shared_state->upstream_node_id = upstream_node_id;
 	LWLockRelease(shared_state->lock);
 
 	PG_RETURN_VOID();
@@ -415,6 +427,27 @@ get_upstream_last_seen(PG_FUNCTION_ARGS)
 }
 
 
+
+Datum
+get_upstream_node_id(PG_FUNCTION_ARGS)
+{
+	int			upstream_node_id = UNKNOWN_NODE_ID;
+
+	if (!shared_state)
+		PG_RETURN_NULL();
+
+	/* A primary node cannot have an upstream ID */
+	if (!RecoveryInProgress())
+		PG_RETURN_INT32(UNKNOWN_NODE_ID);
+
+	LWLockAcquire(shared_state->lock, LW_SHARED);
+	upstream_node_id = shared_state->upstream_node_id;
+	LWLockRelease(shared_state->lock);
+
+	PG_RETURN_INT32(upstream_node_id);
+}
+
+
 /* ===================*/
 /* failover functions */
 /* ===================*/

repmgrd-physical.c

@@ -878,7 +878,7 @@ monitor_streaming_standby(void)
 		log_verbose(LOG_DEBUG, "checking %s", upstream_node_info.conninfo);
 		if (check_upstream_connection(&upstream_conn, upstream_node_info.conninfo) == true)
 		{
-			set_upstream_last_seen(local_conn);
+			set_upstream_last_seen(local_conn, upstream_node_info.node_id);
 		}
 		else
 		{
@@ -1671,7 +1671,7 @@ monitor_streaming_witness(void)
 	{
 		if (check_upstream_connection(&primary_conn, upstream_node_info.conninfo) == true)
 		{
-			set_upstream_last_seen(local_conn);
+			set_upstream_last_seen(local_conn, upstream_node_info.node_id);
 		}
 		else
 		{